Mucin biological role. Human saliva: composition, functions, enzymes

Salivation and salivation are complex processes that occur in the salivary glands. In this article, we will also look at all the functions of saliva.

Salivation and its mechanisms are, unfortunately, not well understood. Probably, the formation of saliva of a certain qualitative and quantitative composition occurs due to a combination of filtration of blood components into the salivary glands (for example: albumins, immunoglobulins C, A, M, vitamins, drugs, hormones, water), selective excretion of some of the filtered compounds into the blood (for example, some blood plasma proteins), additional introduction into the saliva of components synthesized by the salivary gland itself into the blood (for example, mucins).

Factors affecting salivation

Therefore, salivation can change as systemsnye factors, i.e. factors that change the composition of the blood (for example, the intake of fluorine with water and food), and factors local that affect the functioning of the salivary glands themselves (for example, inflammation of the glands). In general, the composition of secreted saliva qualitatively and quantitatively differs from that of blood serum. Thus, the content of total calcium in saliva is approximately twice as low, and the content of phosphorus is twice as high as in blood serum.

Salivation regulation

Salivation and salivation are regulated only reflexively (conditioned reflex to the sight and smell of food). During most of the day, the frequency of neuroimpulses is low and this provides the so-called baseline or “unstimulated” level of saliva flow.

When eating, in response to taste and chewing stimuli, there is a significant increase in the number of neuroimpulses and secretion is stimulated.

Saliva secretion rate

The rate of secretion of mixed saliva at rest averages 0.3-0.4 ml/min, stimulation by chewing paraffin increases this figure to 1-2 ml/min. The rate of unstimulated salivation in smokers with an experience of up to 15 years before smoking is 0.8 ml / min, after smoking - 1.4 ml / min.

Compounds contained in tobacco smoke (over 4 thousand different compounds, including about 40 carcinogens) irritate the tissue of the salivary glands. A significant smoking experience leads to the depletion of the autonomic nervous system, which is in charge of the salivary glands.

Local factors

• hygienic condition of the oral cavity, foreign bodies in the oral cavity (dentures)
• the chemical composition of food due to its residues in the oral cavity (loading food with carbohydrates increases their content in the oral fluid)
• condition of the oral mucosa, periodontium, hard tissues of teeth

Daily biorhythm of salivation

Daily biorhythm: salivation decreases at night, this creates optimal conditions for the vital activity of microflora and leads to a significant change in the composition of organic components. It is known that the rate of saliva secretion determines caries resistance: the higher the rate, the more resistant teeth are to caries.

salivation disorder

The most common impaired salivation is decreased secretion (hypofunction). The presence of hypofunction may indicate a side effect of drug treatment, a systemic disease (diabetes mellitus, diarrhea, febrile conditions), hypovitaminosis A, B. A true decrease in salivation may not only affect the condition of the oral mucosa, but also reflect pathological changes in salivary glands.

Xerostomia

Term "xerostomia" refers to the patient's feeling of dryness in the mouth. Xerostomia is rarely the only symptom. It is associated with oral symptoms that include increased thirst, increased fluid intake (especially with meals). Sometimes patients complain of burning, itching in the mouth (“burning mouth syndrome”), oral infection, difficulty wearing removable dentures, and abnormal taste sensations.

Hypofunction of the salivary gland

In cases where salivation is insufficient, we can talk about hypofunction. Dryness of the tissues lining the oral cavity is the main feature hypofunction of the salivary gland. The oral mucosa may look thin and pale, have lost its luster, and be dry when touched. The tongue or speculum may adhere to soft tissues. It is also important to increase the incidence of dental caries, the presence of oral infections, especially candidiasis, the formation of fissures and lobules on the back of the tongue, and sometimes swelling of the salivary glands.

Increased salivation

Salivation and salivation increase with foreign bodies in the oral cavity between meals, increased excitability of the autonomic nervous system. A decrease in the functional activity of the autonomic nervous system leads to stagnation and the development of atrophic and inflammatory processes in the organs of salivation.

Functions of saliva

saliva functions, which is 99% water and 1% soluble inorganic and organic compounds.

1. digestive
2. Protective
3. Mineralizing

Digestive function of saliva, associated with food, is provided by the stimulated flow of saliva during the meal itself. Stimulated saliva is secreted under the influence of taste bud stimulation, chewing, and other excitatory stimuli (for example, as a result of the gag reflex). Stimulated saliva differs from unstimulated saliva both in the rate of secretion and in composition. The secretion rate of stimulated saliva varies widely from 0.8 to 7 ml/min. The activity of secretion depends on the nature of the stimulus.

Thus, it has been established that salivation can be mechanically stimulated (for example, by chewing gum, even without flavoring). However, such stimulation is not as active as stimulation due to taste stimuli. Among the taste stimulants, acids (citric acid) are most effective. Among the enzymes of stimulated saliva, amylase is predominant. 10% of protein and 70% of amylase is produced by the parotid glands, the rest is mainly produced by the submandibular glands.

Amylase- calcium-containing metalloenzyme from the group of hydrolases, ferments carbohydrates in the oral cavity, helps to remove food debris from the surface of the teeth.

alkaline phosphatase produced by small salivary glands, plays a specific role in tooth formation and remineralization. Amylase and alkaline phosphatase are classified as marker enzymes that provide information on the secretion of large and small salivary glands.

The protective function of saliva

Protective function aimed at preservation of the integrity of the tissues of the oral cavity is provided, first of all, by unstimulated saliva (at rest). The rate of its secretion averages 0.3 ml/min., however, the rate of secretion can be subject to quite significant daily and seasonal fluctuations.

The peak of unstimulated secretion occurs in the middle of the day, and at night, secretion decreases to values ​​​​less than 0.1 ml / min. The protective mechanisms of the oral cavity are divided into 2 groups: non-specific protective factors, acting in general against microorganisms (alien), but not against specific representatives of the microflora, and specific(specific immune system), affecting only certain types of microorganisms.

Saliva contains mucin is a complex protein, glycoprotein, contains about 60% carbohydrates. The carbohydrate component is represented by sialic acid and N-acetylgalactosamine, fucose and galactose. Mucin oligosaccharides form o-glycosidic bonds with serine and threonine residues in protein molecules. Mucin aggregates form structures that firmly hold water inside the molecular matrix, due to which mucin solutions have a significant viscosity. Removal of sialic acids significantly reduces the viscosity of mucin solutions. Oral liquid with a relative density of 1.001 -1.017.

saliva mucins

saliva mucins cover and lubricate the surface of the mucous membrane. Their large molecules prevent bacterial adherence and colonization, protect tissues from physical damage, and allow them to resist thermal shocks. Some haze in saliva due to the presence of cellular elements.

Lysozyme

A special place belongs to lysozyme, synthesized by the salivary glands and leukocytes. Lysozyme (acetylmuramidase)- an alkaline protein that acts as a mucolytic enzyme. It has a bactericidal effect due to the lysis of muramic acid, a component of bacterial cell membranes, stimulates the phagocytic activity of leukocytes, and participates in the regeneration of biological tissues. Heparin is a natural inhibitor of lysozyme.

lactoferrin

lactoferrin has a bacteriostatic effect due to the competitive binding of iron ions. Sialoperoxidase in combination with hydrogen peroxide and thiocyanate, it inhibits the activity of bacterial enzymes and has a bacteriostatic effect. Histatin has antimicrobial activity against Candida and Streptococcus. Cystatins inhibit the activity of bacterial proteases in saliva.

Mucosal immunity is not a simple reflection of general immunity, but is due to the function of an independent system that has an important effect on the formation of general immunity and the course of the disease in the oral cavity.

Specific immunity is the ability of a microorganism to selectively respond to antigens that have entered it. The main factor of specific antimicrobial protection are immune γ-globulins.

Secretory immunoglobulins in saliva

In the oral cavity, IgA, IgG, IgM are most widely represented, but the main factor of specific protection in saliva is secretory immunoglobulins (mainly class A). Violate bacterial adhesion, support specific immunity against pathogenic oral bacteria. The species-specific antibodies and antigens that make up saliva correspond to the human blood type. The concentration of group antigens A and B in saliva is higher than in blood serum and other body fluids. However, in 20% of people, the amount of group antigens in saliva may be low or completely absent.

Class A immunoglobulins are represented in the body by two varieties: serum and secretory. Serum IgA differs little from IgC in its structure and consists of two pairs of polypeptide chains connected by disulfide bonds. Secretory IgA is resistant to various proteolytic enzymes. There is an assumption that enzyme-sensitive peptide bonds in secretory IgA molecules are closed due to the addition of a secretory component. This resistance to proteolysis is of great biological importance.

IgA are synthesized in the plasma cells of the lamina propria and in the salivary glands, and the secretory component in the epithelial cells. To get into the secrets, IgA must overcome the dense epithelial layer lining the mucous membranes; immunoglobulin A molecules can pass this way both through the intercellular spaces and through the cytoplasm of epithelial cells. Another way for the appearance of immunoglobulins in secrets is their entry from the blood serum as a result of extravasation through an inflamed or damaged mucous membrane. The squamous epithelium lining the oral mucosa acts as a passive molecular sieve, especially favoring IgG penetration.

Mineralizing function of saliva.saliva minerals very varied. The largest amount contains ions Na +, K +, Ca 2+, Cl -, phosphates, bicarbonates, as well as many trace elements such as magnesium, fluorine, sulfates, etc. Chlorides are amylase activators, phosphates are involved in the formation of hydroxyapatites, fluorides - hydroxyapatite stabilizers. The main role in the formation of hydroxyapatites belongs to Ca 2+ , Mg 2+ , Sr 2+ .

Saliva serves as a source of calcium and phosphorus entering the tooth enamel, therefore, saliva is normally a mineralizing liquid. The optimum Ca/P ratio in enamel, necessary for mineralization processes, is 2.0. A decrease in this coefficient below 1.3 contributes to the development of caries.

Mineralizing function of saliva consists in influencing the processes of mineralization and demineralization of enamel.

The enamel-saliva system can theoretically be considered as a system: HA crystal ↔ HA solution(solution of Ca 2+ and HPO 4 2- ions),

C process speed ratioThe rate of dissolution and crystallization of HA enamel at a constant temperature and area of ​​contact between the solution and the crystal depends only on the product of the molar concentrations of calcium and hydrophosphate ions.

Dissolution and crystallization rate

If the rates of dissolution and crystallization are equal, as many ions pass into the solution as they precipitate into the crystal. The product of molar concentrations in this state - the state of equilibrium - is called solubility product (PR).

If in a solution [Ca 2+ ] [HPO 4 2- ] = PR, the solution is considered saturated.

If in solution [Ca 2+ ] [HPO 4 2- ]< ПР, раствор считается ненасы­щенным, то есть происходит растворение кристаллов.

If in solution [Ca 2+ ] [HPO 4 2- ] > PR, the solution is considered supersaturated, crystals grow.

The molar concentrations of calcium and hydrophosphate ions in saliva are such that their product is greater than the calculated PR required to maintain equilibrium in the system: HA crystal ↔ HA solution (solution of Ca 2+ and HPO 4 2- ions).

Saliva is supersaturated with these ions. Such a high concentration of calcium and hydrophosphate ions contributes to their diffusion into the enamel fluid. Due to this, the latter is also a supersaturated solution of HA. This provides the benefit of enamel mineralization as it matures and remineralizes. This is the essence of the mineralizing function of saliva. The mineralizing function of saliva depends on the pH of saliva. The reason is a decrease in the concentration of bicarbonate ions in saliva due to the reaction:

HPO 4 2- + H + H 2 PO 4 –

Dihydrophosphate ions H 2 RO 4 - unlike hydrophosphate HPO 4 2-, do not give HA when interacting with calcium ions.

This leads to the fact that saliva turns from a supersaturated solution to a saturated or even unsaturated solution with respect to HA. In this case, the dissolution rate of HA increases, i.e. demineralization rate.

saliva pH

A decrease in pH can occur with an increase in the activity of microflora due to the production of acidic metabolic products. The main acidic product produced is lactic acid, which is formed during the breakdown of glucose in bacterial cells. The increase in the rate of enamel demineralization becomes significant when the pH drops below 6.0. However, such a strong acidification of saliva in the oral cavity rarely occurs due to the work of buffer systems. More often there is a local acidification of the environment in the area of ​​soft plaque formation.

An increase in the pH of saliva relative to the norm (alkalinization) leads to an increase in the rate of enamel mineralization. However, this also increases the rate of tartar deposition.

Staterins in saliva

A number of salivary proteins contribute to the remineralization of subsurface enamel lesions. Staterins (proline-containing proteins) and a number of phosphoproteins prevent the crystallization of minerals in saliva, maintain saliva in a state of supersaturated solution.

Their molecules have the ability to bind calcium. When the pH in plaque falls, they release calcium and phosphate ions into the liquid phase of plaque, thus contributing to increased mineralization.

Thus, normally, two oppositely directed processes occur in enamel: demineralization due to the release of calcium and phosphate ions and mineralization due to the incorporation of these ions into the HA lattice, as well as the growth of HA crystals. A certain ratio of the rate of demineralization and mineralization ensures the maintenance of the normal structure of the enamel, its homeostasis.

Homeostasis is determined mainly by the composition, rate of secretion and physicochemical properties of the oral fluid. The transition of ions from the oral fluid into HA enamel is accompanied by a change in the rate of demineralization. The most important factor affecting enamel homeostasis is the concentration of protons in the oral fluid. A decrease in the pH of the oral fluid can lead to increased dissolution, demineralization of enamel

Saliva buffer systems

Saliva buffer systems represented by bicarbonate, phosphate and protein systems. Saliva pH ranges from 6.4 to 7.8, within a wider range than blood pH and depends on a number of factors - the hygienic condition of the oral cavity, the nature of the food. The most powerful destabilizing pH factor in saliva is the acid-forming activity of the oral microflora, which is especially enhanced after carbohydrate intake. An “acidic” reaction of the oral fluid is observed very rarely, although a local decrease in pH is a natural phenomenon and is due to the vital activity of the microflora of dental plaque and carious cavities. At a low rate of secretion, the pH of saliva shifts to the acid side, which contributes to the development of caries (pH<5). При стиму­ляции слюноотделения происходит сдвиг рН в щелочную сторону.

The microflora of the oral cavity

The microflora of the oral cavity is extremely diverse and includes bacteria (spirochetes, rickettsiae, cocci, etc.), fungi (including actinomycetes), protozoa, and viruses. At the same time, a significant part of the microorganisms of the oral cavity of adults are anaerobic species. The microflora is discussed in detail in the course of microbiology.

Article for the competition "bio/mol/text": Mucins are the main glycoproteins of the mucus that covers the respiratory, digestive, and urinary tracts. The mucus layer protects against infection, dehydration, physical and chemical damage, and also acts as a lubricant and facilitates the passage of substances through the tract. But something else is interesting: it turns out that by changing the level of mucin production in the epithelial cells of various organs - the lungs, prostate, pancreas and others - one can judge the development of oncological processes hidden for the time being. This is especially true when there are difficulties in diagnosing cancer and in determining the source of tumor cells during metastasis.

Note!

The sponsor of the nomination "The Best Article on the Mechanisms of Aging and Longevity" is the Science for Life Extension Foundation. The Audience Choice Award was sponsored by Helicon.

Contest sponsors: 3D Bioprinting Solutions Laboratory for Biotechnology Research and Visual Science Studio for Scientific Graphics, Animation and Modeling.

Figure 1. Secreted and membranous forms of mucins in the protective barrier of the epithelium. a - Secreted mucins form a protective surface gel over epithelial cells. MUC2 is the most abundant mucin in the gastrointestinal mucosa. b - Transmembrane mucins are exposed on the surface of epithelial cells, where they form part of the glycocalyx. The sites with tandem amino acid repeats at the N-terminus are rigidly fixed above the glycocalyx, and when they are torn off, mucin subunits are opened in MUC1 and MUC4, which can transmit a stress signal into the cell. Drawing from .

In the mucous membrane, mucins perform an important protective function. They help the body cleanse itself of unwanted substances, keep distance from pathogenic organisms, and even regulate the behavior of the microbiota. In the intestine, for example, mucoproteins are involved in the dialogue between bacteria and mucosal epithelial cells. The microbiota, through epithelial cells, influences the production of mucins (Fig. 2), which, in turn, may be involved in the transmission of inflammatory signals. Bacteriophages are attached to mucin glycans, which also contribute to the regulation of bacterial numbers. The carbohydrate chains of mucoproteins perfectly bind water, forming a dense layer and thus keeping antimicrobial proteins from being flushed into the intestinal lumen. Of course, in the mucosa of the gastrointestinal tract (and not only) mucoproteins are not the main protective mechanism. In addition to mucins, antimicrobial peptides, secreted antibodies, glycocalyx, and other structures are involved in defense.

Figure 2. Influence of the microbiota on mucus secretion. Bacteria - commensals of the large intestine during the catabolism of indigestible carbohydrates in the small intestine form short-chain fatty acids ( SCFA, short-chain fatty acids), such as acetate, propionate and butyrate, which increase the production of mucins and the protective function of the epithelium. Drawing from .

With prolonged stress on the cell, its cancerous transformation is possible. Under the influence of stress, the cell can lose its polarity, as a result of which its apical transmembrane molecules, among which mucins are also present, begin to be exposed on the basolateral surfaces. In these places, mucins are unwanted guests, since their nonspecific binding to other molecules and receptors can lead to disruption of intercellular and basal contacts. MUC4, for example, contains an EGF-like domain capable of binding to a neighboring cell's tyrosine kinase receptor and leading to disruption of tight junctions. Deprived of connection with the environment, a depolarized cell has every chance of becoming cancerous, if it is not already.

Figure 3. Structure of the mucoprotein MUC1. ST- cytoplasmic domain, TM- transmembrane domain. Drawing from .

In the diagnosis of certain types of malignant tumors, the profile of mucins produced by cells is studied. The fact is that the expression of genes of different types of mucoproteins during the development of the organism has a specific spatio-temporal framework. However, unregulated expression of some of these genes is often observed in oncological diseases. For example, MUC1 (Fig. 3) is a marker for bladder cancer in certain amounts. In pathology, the concentration of MUC1 increases significantly, and the structure of the mucoprotein also changes. By influencing cell metabolism through tyrosine kinase and other receptors, MUC1 enhances the production of cell growth factors.

However, the assessment of the serum level of MUC1 is not very sensitive, although it is a highly specific method for diagnosing bladder cancer, not suitable for screening, but suitable for monitoring progression. It was also established that a favorable outcome of the disease is associated with hyperproduction of the receptor for the epidermal growth factor HER3 against the background of an increased content of MUC1. Only with the help of a cumulative analysis of these markers can any forecasts be made.

Further studies related to this mucin will be devoted to the study of the influence of MUC1 interactions with various factors and receptors on the course of the disease. In addition, the gene locus responsible for the synthesis of the MUC1 molecule has already been identified. This locus is considered as a possible target for gene therapy in order to reduce the risk of developing a primary tumor and its metastasis*.

* - Details about genetic therapy are described in the article " Gene therapy against cancer» .

Another study found that abnormal expression of the gene encoding MUC4 is a marker for pancreatic cancer. The gene of this mucin was significantly expressed in cancer cells, but not in the tissues of a normal or even inflamed gland (in chronic pancreatitis). The scientists used reverse transcription PCR as their main diagnostic method. In the same way, they also assessed the level of MUC4 mRNA synthesis in the monocytic fraction of the peripheral blood of patients: after all, it would be the easiest way to screen in clinics if successful. Such an analysis turned out to be a reliable way to detect pancreatic adenocarcinoma in the early stages. In healthy people and in tumors of other organs, gene expression MUC4 not fixed.

The discovery that transmembrane mucins are associated with cellular transformation and can contribute to tumor development marked the beginning of a new direction in the study of anticancer agents - so far in preclinical studies.

An increase in the production of mucins can be observed in a variety of diseases affecting the mucous membranes. However, in some cases, the gene expression profile of different mucins may be associated with a specific pathology. And among the numerous structural transformations of mucins characteristic of cancer, one can single out those that will become the most specific markers for the routine detection of a particular tumor.

Literature

1. Behera S.K., Praharaj A.B., Dehury B., Negi S. (2015). Exploring the role and diversity of mucins in health and disease with special insight into non-communicable diseases. Glycoconj. J. 32 , 575-613;
2. Kufe D.W. (2009). Mucins in cancer: function, prognosis and therapy. Nat. Rev. Cancer. 9 , 874-885;
3. Linden S.K., Sutton P., Karlsson N.G., Korolik V., McGuckin M.A. (2008). Mucins in the mucosal barrier to infection. Mucosal Immunol. 1 , 183-197;
4. Shan M., Gentile M., Yeiser J.R., Walland A.C., Bornstein V.U., Chen K. et al. (2013). Mucus enhances gut homeostasis and oral tolerance by delivering immunoregulatory signals. Science. 342 , 447-453;
5. Kamada N., Seo S.U., Chen G.Y., Núñez G. (2013). Role of the gut microbiota in immunity and inflammatory disease. Nat. Rev. Immunol. MUC) gene expression in human pancreatic adenocarcinoma and chronic pancreatitis: a potential role of MUC4 as a tumor marker of diagnostic significance. Clin. Cancer Res. 7 , 4033-4040;
6. Brayman M., Thathiah A., Carson D.D. (2004). MUC1: A multifunctional cell surface component of reproductive tissue epithelia. reproduction. Biol. Endocrinol. 2 , 4..

Features of the composition, properties, dependence on the stimulation of salivation. Physiological role of saliva.
Mixed saliva (oral fluid) is a viscous (due to the presence of glycoproteins) liquid. Saliva pH fluctuations depend on the hygienic state of the oral cavity, the nature of food, and the rate of secretion. At a low rate of secretion, the pH of saliva shifts to the acid side, and when salivation is stimulated, it shifts to the alkaline side.
Saliva is produced by three pairs of large salivary glands and many small glands of the tongue, mucous membrane of the palate and cheeks. From the glands through the excretory ducts, saliva enters the oral cavity. Depending on the set and intensity of secretion of different glandulocytes in the glands, they secrete saliva of different composition. Parotid-25% and small glands of the lateral surfaces of the tongue, containing a large number of serous cells, secrete liquid saliva with a high concentration of sodium and potassium chlorides and high amylase activity. A liquid protein secretion is isolated. Small salivary glands produce thicker and more viscous saliva containing glycoproteins. The secret of the submandibular gland - 70% (mixed protein-mucous secret) is rich in organic substances, including mucin, contains amylase, but in a lower concentration than the saliva of the parotid gland. The saliva of the sublingual gland 3-4% (mixed protein-mucous secret) is even richer in mucin, has a pronounced alkaline reaction, high phosphatase activity. The secretion of the mucous glands located at the root of the tongue and palate is especially viscous due to the high concentration of mucin. There are also small mixed glands. The amount of saliva secreted is variable and depends on the state of the body, the type and smell of food.
Physiological role of saliva.
-wetting and softening food
- lubricating function
-digestive
- protective
- enamel mineralization
- maintaining optimal pH
-regulatory
-excretory

2. Enzymes of saliva - alpha amylase, lysozyme, peroxidase, phosphatase, peptidyl peptidase, etc. Their origin and significance.
Amylase
-Calcium-containingmetalloenzyme.
- Hydrolyzes internal 1,4-glycosidic bonds in starch and similar polysaccharides.
- There are several isoenzymes-amylase.
- Maltose is the main end productdigestion.
-excreted with the secretion of the parotid gland and labial small glands
-not related to age, but varies throughout the day and depends on food intake
Lysozyme
- Globular protein with a mol. weighing 14 kDa.

It is secreted by epithelial cells of the ducts of the salivary glands and neutrophilic leukocytes.

Acts as an antimicrobial agent against Gram+ and Gram- bacteria, fungi and some viruses.

The mechanism of the antimicrobial effect is associated with the ability of lysozyme to hydrolyze the glycosidic bond between N-acetylglucosamine and N-acetylmuramic acid.
-(NANA-NAMA) in bacterial cell wall polysaccharides.

peroxidase and catalase
-iron-porphyrin enzymes of antibacterial action
-oxidize substrates using hydrogen peroxide as an oxidizing agent
- salivary peroxidase has several isoforms
- saliva has a high peroxidase activity
Myeloperoxidase is derived from neutrophilic leukocytes
-catalase is of bacterial origin
catase breaks down hydrogen peroxide to form oxygen and water
Alkaline phosphatase
-hydrolyzes phosphoric acid esters
- activates the mineralization of bone tissue and teeth
- the source of the enzyme is the sublingual glands
acid phosphatase
source are parotid glands, leukocytes and microorganisms
- there are 4 isoforms of acid phosphatase
- activates the processes of demineralization of tooth tissues and resorption of periodontal bone tissue
Cabroanhydrase
-belongs to the class of lyases
- catalyzes the cleavage of the C-O bond in carbonic acid, which leads to the formation of CO2 and H2O molecules
- its concentration is very low during sleep and increases during the daytime, after waking up and having breakfast
-regulates the buffer capacity of saliva
- accelerating the removal of acids from the surface of the tooth, it protects tooth enamel from demineralization
Cystatins
- Family of 8 proteinsderived from a common precursor.
- They are phosphoproteinsmolecular weight 9-13 kDa.
- Contains various groupspossessing the properties of powerful inhibitors of bacterial proteinases.
- 2 types of cystatins are found in the composition of the dental pellicle.
Nucleases (RNases and DNases)

Play an important role in the protective function of mixed saliva
source is leukocytes
- acidic and alkaline RNases and DNases were found in saliva, differing in various functions
- in some inflammatory processes of the soft tissues of the oral cavity, their number increases

3. Non-protein low molecular weight components of saliva: glucose, carboxylic acids, lipids, vitamins, etc.

4. Inorganic components of saliva, their distribution in stimulated and unstimulated saliva, cationic and anionic composition. Calcium, phosphorus, thiocyanates. saliva pH. Saliva buffer systems. Causes and significance of acidotic pH shift.
The inorganic components that make up saliva are represented by anions Cl, PO4, HCO3, SCN, I, Br, F, SO4, cations Na, K, Ca, Mg and trace elements Fe, Cu, Mn, Ni, Li, Zn, Cd, Pb, Li, etc. all mineral macro-microelements are found both in the form of simple ions and in the composition of compounds - salts, proteins and chelates.
HCO3 anions are excreted by active transport from the parotid and submandibular salivary glands and determine the buffer capacity of saliva. The concentration of HCO3 saliva "rest" is 5 mmol/l, and in the stimulated-60 mmol/l.
Na and K ions enter the mixed saliva with the secretion of the parotid and submandibular salivary glands. Saliva from the submandibular glands contains 8-14 mmol/l K and 6-12 mmol/l Na. In the parotid saliva, an even greater amount of K is determined - about 25-49 mmol / l and much less sodium - only 2-8 mmol / l.

Saliva is oversaturated with phosphorus and calcium ions. Phosphate is found in two forms: in the form of "inorganic" phosphate and associated with proteins and other compounds. The content of total phosphate in saliva reaches 7.0 mmol / l, of which 70-95% falls on the share of inorganic phosphate (2.2-6.5 mmol / l), which is presented in the form of monohydrophosphate - HPO 4 - and dihydrogen phosphate - H 2 RO 4 - . The concentration of monohydrophosphate varies from below 1 mmol/l in saliva "rest" to 3 mmol/l in stimulated saliva. The concentration of dihydrogen phosphate in the "rest" saliva reaches 7.8 mmol/l, and in the stimulated saliva it becomes less than 1 mmol/l.

The content of calcium in saliva is different and ranges from 1.0 to 3.0 mmol/l. Calcium, like phosphates, is in an ionized form and in combination with proteins. There is a correlation coefficient Ca 2+ /Ca total, which is equal to 0.53-0.69.
This concentration of calcium and phosphate is necessary to maintain the constancy of tooth tissues. This mechanism proceeds through three main processes: pH regulation; an obstacle in the dissolution of tooth enamel; incorporation of ions into mineralized tissues.

An increase in blood plasma to non-physiological values ​​of heavy metal ions is accompanied by their excretion through the salivary glands. Heavy metal ions that enter the oral cavity with saliva interact with hydrogen sulfide molecules released by microorganisms and metal sulfides are formed. This is how a “lead border” appears on the surface of the enamel of the teeth.

When urea is destroyed by urease of microorganisms, an ammonia molecule (NH 3) is released into the mixed saliva. Thiocyanates (SCN - , thiocyanates) enter the saliva from the blood plasma. Thiocyanites are formed from hydrocyanic acid with the participation of the enzyme rhodanese. The saliva of smokers contains 4-10 times more thiocyanate than non-smokers. Their number can also increase with inflammation of the periodontium. With the breakdown of iodothyronines in the salivary glands, iodides are released. The amount of iodides and thiocyanates depends on the rate of salivation and decreases with an increase in saliva secretion.

Saliva buffer systems.
Buffer systems are such solutions that are able to maintain a constant pH environment when they are diluted or a small amount of acids and bases are added. A decrease in pH is called acidosis, and an increase is called alkalosis.
Mixed saliva contains three buffer systems: hydrocarbonate, phosphate and protein. Together, these buffer systems form the first line of defense against acidic or alkaline attack on oral tissues. All buffer systems of the oral cavity have different capacity limits: phosphate is most active at pH 6.8-7.0, hydrocarbonate at pH 6.1-6.3, and protein provides buffer capacity at various pH values.

The main buffer system of saliva is hydrocarbonate , which is a conjugated acid-base pair, consisting of a molecule H 2 CO 3 - a proton donor, and a hydrocarbonation HCO 3 - a proton acceptor.

During eating, chewing, the buffer capacity of the hydrocarbon system is provided on the basis of equilibrium: CO 2 + H 2 O \u003d HCO 3 + H +. Chewing is accompanied by an increase in salivation, which leads to an increase in

measuring the concentration of bicarbonate in saliva. When acid is added, the phase of CO 2 transition from dissolved gas to free (volatile) gas increases significantly and increases the efficiency of neutralizing reactions. Due to the fact that the end products of the reactions do not accumulate, complete removal of acids occurs. This phenomenon is called "buffer phase".

With prolonged standing of saliva, a loss of CO 2 occurs. This feature of the hydrocarbon system is called the buffering stage, and it continues until more than 50% of the hydrocarbon is used up.

After exposure to acids and alkalis, H 2 CO 3 quickly decomposes to CO 2 and H 2 O. The dissociation of carbonic acid molecules occurs in two stages:

H 2 CO 3 + H 2 O HCO 3 - + H 3 O + HCO 3 - + H 2 O CO 3 2- + H 3 O +

Phosphate buffer system saliva is a conjugated acid-base pair, consisting of a dihydrogen phosphate ion H 2 PO 2- (proton donor) and a monohydrophosphate ion - HPO 4 3- (proton acceptor). The phosphate system is less efficient than the hydrocarbon system and does not have the "buffer phase" effect. The concentration of HPO 4 3- in saliva is not determined by the rate of salivation, so the capacity of the phosphate buffer system does not depend on food intake or chewing.

The reactions of the components of the phosphate buffer system with acids and bases proceed as follows:

When adding acid: HPO 4 3- + H 3 O + H 2 PO 2- + H 2 O

When adding a base: H 2 PO 2- + OH - HPO 4 3- + H 2 O

Protein buffer system has an affinity for biological processes occurring in the oral cavity. It is represented by anionic and cationic proteins, which are highly soluble in water. This buffer system includes more than 944 different proteins, but it is not completely known which proteins are involved in the regulation of acid-base balance. Carboxyl groups of aspartate, glutamate radicals, as well as cysteine, serine and tyrosine radicals are proton donors

In this regard, the protein buffer system is effective at both pH 8.1 and pH 5.1.

The pH of “resting” saliva differs from the pH of stimulated saliva. Thus, the unstimulated secretion from the parotid and submandibular salivary glands has a moderately acidic pH (5.8), which increases to 7.4 with subsequent stimulation. This shift coincides with an increase in the amount of HCO 3 in saliva - up to 60 mmol/l.

Thanks to buffer systems, in practically healthy people, the pH level of mixed saliva is restored after eating to its original value within a few minutes. With the failure of buffer systems, the pH of mixed saliva decreases, which is accompanied by an increase in the rate of enamel demineralization and initiates the development of a carious process.

The pH of saliva is largely influenced by the nature of the food: when taking orange juice, coffee with sugar, strawberry yogurt, the pH drops to 3.8-5.5, while drinking beer, coffee without sugar practically does not cause changes in saliva pH .
The reasons:
Usually, the products of oxidation of organic acids are quickly removed from the body. With febrile illnesses, intestinal disorders, pregnancy, starvation, etc., they linger in the body, which is manifested in mild cases by the appearance in the urine acetoacetic acid and acetone (so-called. acetonuria), and in heavy ones (for example, with diabetes) can lead to coma.
5. Saliva proteins. General characteristics. Mucin, immunoglobulins, other glycoproteins. Specific proteins of saliva. The role of proteins in the functions of saliva.
A number of salivary proteins are synthesized by the salivary glands. They are represented by mucin, proteins rich in proline, immunoglobulins, parotin, lysozyme, histatins, cystatins, lactoferrine, etc. proteins have different molecular weights, mucins and secretory immunoglobulin A have the highest. These saliva proteins form a pellicle on the oral mucosa, which provides lubrication , protect the mucous membrane from the effects of environmental factors and proteolytic enzymes secreted by bacteria and destroyed polymorphonuclear leukocytes, and also prevent its drying.
Mucins

Globular proteins
Mucins are highly hydrophilic (resistant to dehydration).
- Possess unique rheological properties (high viscosity, elasticity, adhesiveness with low solubility).
- There are 2 main types of mucins (MG1 and MG2).
- Lining up in the same direction as the fluid flow, mucin molecules serve as a biological lubricant, reducing the friction force of the moving elements of the oral cavity.
- Can attach to bacterial membrane polysaccharides, creating a mucin membrane around bacterial cells, and thus stop their aggressive action.
Mucins are the main structural components of the dental pellicle.

Immunoglobulins (Ig)

- Antibodies are plasma immunoglobulins (γ-globulins).

Formed in the cells of the immune system (lymphocytes).

All major types ( IgA, IgM, IgG, IgD, IgE) found in oral fluid.

Neutralize antigens of bacteria and viruses.

The main structural units are 2 heavy and

2 light chains linked by interchain disulfide bonds.

Both types of chains contain variable ends involved in antigen recognition and binding.

Histatins

A family of 12 histidine-rich peptides.

Secreted by the parotid and submandibular glands.

Residues of negatively charged amino acids are located near the C-terminus.

They take part in the formation of the dental pellicle.

Inhibit the growth of hydroxyapatite crystals.

Powerful inhibitors of bacterial proteinases.
lactoferrin

A glycoprotein found in many body fluids.

The highest concentration of lactoferrin occurs in saliva and colostrum.

Lactoferrin performs a protective function, because. binds Fe 3+ ions necessary for the growth and reproduction of bacteria.

Lactoferrin is able to change the redox potential of bacteria, which also leads to a bacteriostatic effect.

Proline rich proteins (PRPs)

Like staterin, also asymmetric molecules

Inhibit the growth of calcium phosphate crystals

The inhibition is due to 30 negatively charged amino acid residues near the N-terminus.

PRPs promote bacterial adhesion to the enamel surface:

The C-terminus is responsible for a highly specific interaction with oral fluid bacteria,

The proline-glutamyl dipeptide fragment located at the C-terminus performs this function.
α - and β-defensins

Cysteine-rich peptides with predominantly β-sheet structure.

Produced by leukocytes.

They act as antimicrobial agents against Gram+ and Gram- bacteria, fungi and some viruses.

They can form channels in microbial cells and inhibit protein synthesis in them.
Cathelicidins

Peptides with predominantly α-helical structure.

Found in saliva, mucous secretions and skin.

They can form ion channels in bacterial cells and inhibit protein synthesis.
6. Gingival fluid. Features of its chemical composition.
- Produced in the gingival groove.

Composition similar to interstitial fluid

Intact gum produces JJ at a rate of 0.5-2.4 ml/day

The normal depth of the gingival groove is 3 mm or less.

With periodontitis, the depth of this groove becomes more than 3 mm. In this case, it is called a gum pocket.

Composition J:
1. Cells

desquamated epithelial cells,

neutrophils,

Lymphocytes and monocytes (small number),

bacteria

2. Inorganic ions

Same as in blood plasma

Fluorine (J - source F - for mineralization)

3.Organic components

Proteins (concentration 61-68 g/l)

Proteins - the same as in plasma - serum albumin, globulins, complement, protease inhibitors (lactoferrin), immunoglobulins A, M, G,

Low molecular weight substances - lactate, urea, hydroxyproline,

Enzymes (cellular and extracellular)
J functions:

Purifying - The movement of this fluid flushes out potentially dangerous cells and bacteria.

Antibacterial- immunoglobulins, lactoferrin.

Remineralizing- Ca 2+, PO 3 H 2 - and F - ions,

Calcium and phosphorus are involved in the formation of the pellicle, but can lead to the formation of tartar,

Antioxidant- J contains the same antioxidants as the general oral fluid.

Mucins (from lat. mucus - mucus)

secretions (secrets) of epithelial cells of the mucous membranes of the respiratory, digestive, urinary tract, as well as submandibular and sublingual salivary glands. According to the chemical nature of M. - a mixture of carbohydrate-protein compounds - glycoproteins (See Glycoproteins). Provide mucous membranes with moisture, elasticity; M. saliva contribute to the wetting and gluing of the food bolus and its passage through the esophagus. Enveloping the mucous membrane of the stomach and intestines, M. protect it from the effects of proteolytic enzymes of gastric and intestinal juice. They perform a protective function in the body, for example, they suppress the adhesion (hemagglutination (See Hemagglutination)) of red blood cells caused by the influenza virus.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Mucins" are in other dictionaries:

- (from Latin mucus mucus), mucoproteins are a family of high molecular weight glycoproteins containing acidic polysaccharides. They have a gel-like consistency and are produced by the epithelial cells of almost all animals, including humans. Mucins are the main ... ... Wikipedia

- (from Latin mucus mucus) glycoproteins that are part of the viscous secretions of the mucous membranes of animals, as well as saliva, gastric and intestinal juices. Provides moisture and elasticity to the mucous membranes… Big Encyclopedic Dictionary

Complex proteins (glycoproteins) that are part of the secretions of the mucous glands. Contains ch. arr. acidic polysaccharides linked to proteins by ionic bonds. Fucomucins (high in fucose) are found in most secretions of the mucous glands ... ... Biological encyclopedic dictionary

mucins- ov, pl. (unit mucin, a, m.). mucine lat. mucus mucus. Semi-liquid, transparent, viscous substances that are part of the secretions of mucous membranes, saliva, gastric and intestinal juices. ALS 3. Lex. Michelson 1866: mucin; TSB 2: mucins / ny ... Historical Dictionary of Gallicisms of the Russian Language

- (from Latin mucus mucus), glycoproteins that are part of the viscous secretions of the mucous membranes of animals, as well as saliva, gastric and intestinal juices. Provide moisture and elasticity of mucous membranes. * * * MUCINS MUCINS (from lat. mucus… … encyclopedic Dictionary

Mn. Semi-liquid, transparent, viscous substances that are part of the secretions of mucous membranes, saliva, gastric and intestinal juices. Explanatory Dictionary of Efremova. T. F. Efremova. 2000... Modern explanatory dictionary of the Russian language Efremova

- (from lat. mucus mucus), glycoproteins that are part of the viscous secretions of the mucous membranes of the stomach, as well as saliva, gastric and intestinal juices. Provides moisture and elasticity to the mucous membranes… Natural science. encyclopedic Dictionary

The condition of the hard and soft tissues of the oral cavity is determined by the amount and properties of saliva, which is secreted by the salivary glands located in the anterior part of the human digestive tract.

Numerous small salivary glands are located in the mucous membrane of the tongue, lips, cheeks, hard and soft palate. Outside the oral cavity there are 3 pairs of large glands - parotid, sublingual and submandibular and communicate with it through ducts.

6.1. STRUCTURE AND FUNCTIONS OF THE SALIVARY GLANDS

The large salivary glands are alveolar-tubular and consist of secretory sections and a system of pathways that bring saliva into the oral cavity.

In the parenchyma of the salivary glands, a terminal section and a system of excretory ducts are distinguished. The end sections are represented by secretory and myoepithelial cells, which communicate through desmosomes with secretory cells and contribute to the removal of secretions from the end sections. The terminal sections pass into the intercalary ducts, and they, in turn, into the striated ducts. The cells of the latter are characterized by the presence of elongated mitochondria located perpendicular to the basement membrane. Secretory granules are present in the apical parts of these cells. One-way saliva transport is provided by reservoir and valve structures, as well as muscle elements.

Depending on the composition of the secreted saliva, protein, mucous and mixed secretory sections are distinguished. The parotid salivary glands and some glands of the tongue secrete a liquid protein secretion. Small salivary glands produce thicker and more viscous saliva containing glycoproteins. The submandibular and sublingual, as well as the salivary glands of the lips, cheeks and tip of the tongue, secrete a mixed protein-mucous secret. Most of the saliva is formed by the submandibular salivary glands (70%), parotid

(25%), sublingual (4%) and small (1%). Such saliva is called saliva proper or flowing saliva.

Functions of the salivary glands

secretory function . As a result of the secretory activity of the large and small salivary glands, the oral mucosa is moistened, which is a necessary condition for the implementation of bilateral transport of chemicals between the oral mucosa and saliva.

Excretory (endocrine) function . Various hormones are excreted with saliva - glucagon, insulin, steroids, thyroxine, thyrotropin, etc. Urea, creatinine, derivatives of drugs and other metabolites are injected. The salivary glands have selective transport of substances from the blood plasma into the secretion.

Regulatory (integrative) function . The salivary glands have an endocrine function, which is ensured by the synthesis of parotin and growth factors in it - epidermal, insulin-like, nerve growth, endothelial growth, fibroblast growth, which have both paracrine and autocrine effects. All these substances are excreted both in the blood and in saliva. With saliva in small quantities, they are excreted into the oral cavity, where they contribute to the rapid healing of damage to the mucous membrane. Parotin also has an effect on the epithelium of the salivary glands, stimulating protein synthesis in these cells.

6.2. MECHANISM OF SALIVATION SECRETION

Secretion- the intracellular process of substances entering the secretory cell, the formation of a secret of a certain functional purpose from them, and the subsequent release of the secret from the cell. Periodic changes in the secretory cell associated with the formation, accumulation, secretion, and recovery through further secretion is called the secretory cycle. From 3 to 5 phases of the secretory cycle are distinguished, and each of them is characterized by a specific state of the cell and its organelles.

The cycle begins with the entry of water, inorganic and low molecular weight organic compounds (amino acids, monosaccharides, etc.) into the cell from the blood plasma through pinocytosis, diffusion, and active transport. Substances that enter the cell are used for synthesis

secretory product, as well as for intracellular energy and plastic purposes. In the second phase, the primary secretory product is formed. This phase differs significantly depending on the type of secretion formed. In the final phase, the secretory product is released from the cell. According to the mechanism of salivation by the secretory sections, all salivary glands are exocrine-merocrine. In this case, the secret is released from the cell without destruction of glandular cells in dissolved form through its apical membrane into the lumen of the acinus, and then enters the oral cavity (Fig. 6.1).

Active transport, synthesis and secretion of proteins require energy expenditure of ATP molecules. ATP molecules are formed during the breakdown of glucose in the reactions of substrate and oxidative phosphorylation.

Formation of primary salivary secretion

The secretion of the salivary glands contains water, ions and proteins. The specificity and isolation of secretion products of different composition made it possible to identify secretory cells with three types of intracellular conveyors: protein, mucous, and mineral.

The formation of the primary secret is associated with a number of factors: blood flow through the blood vessels surrounding the secretory sections; salivary glands, even at rest, have a high

Primary secretion of ions from blood plasma (isotonic saliva)

Rice. 6.1.Transport systems in the salivary glands involved in the formation of salivary secretions.

bulk blood flow. With the secretion of the glands and the resulting vasodilation, the blood flow increases by 10-12 times. The blood capillaries of the salivary glands are characterized by high permeability, which is 10 times higher than in the capillaries of skeletal muscles. It is likely that such a high permeability is due to the presence of active kallikrein in the cells of the salivary glands, which breaks down kininogens. The resulting kinins (kallidin and bradykinin) change vascular permeability; flow of water and ions through the pericellular space, opening

channels on the basolateral and apical membranes; contraction of myoepithelial cells located around

secretory sections and excretory ducts. In secretory cells, an increase in the concentration of Ca 2+ ions is accompanied by the opening of calcium-dependent ion channels. Synchronous secretion in acinar cells and contraction of myoepithelial cells leads to the release of primary saliva into the excretory ducts. Secretion of electrolytes and water in secretory cells. The electrolyte composition of saliva and its volume is determined by the activity of acinar cells and duct cells. The transport of electrolytes in acinar cells consists of two stages: the transfer of ions and water through the basolateral membrane into the cell and their exit through the apical membrane into the lumen of the ducts. In the cells of the excretory ducts, not only secretion is carried out, but also the reabsorption of water and electrolytes. The transport of water and ions also occurs in the pericellular space according to the mechanism of active and passive transport.

Ions Ca 2+, Cl - , K + , Na + , PO 4 3-, as well as glucose and amino acids enter the cell through the basolateral membrane. In the future, the latter are used for the synthesis of secretory proteins. The glucose molecule undergoes aerobic decay to the final products CO 2 and H 2 O with the formation of ATP molecules. Most of the ATP molecules are used for the operation of transport systems. With the participation of carbonic anhydrase, CO 2 and H 2 O molecules form carbonic acid, which dissociates into H + and HCO 3 -. The orthophosphate that enters the cell is used to form ATP molecules, and the excess is released through the apical membrane with the help of a carrier protein.

An increase in the concentration of Cl - , Na + ions inside the cell causes a flow of water into the cell, which enters through proteins - aquaporins. Aquaporins provide rapid fluid transport across the membranes of epithelial and endothelial cells. Identified in mammals

11 members of the aquaporin family with cellular and subcellular distribution. Some aquaporins are membrane channel proteins and are present as tetramers. In some cases, aquaporins are located in intracellular vesicles and are transferred to the membrane as a result of stimulation with vasopressin, muscarine (aquaporin-5). Aquaporins -0, -1, -2, -4, -5, -8, -10 selectively pass water; aquaporins -3, -7, -9 not only water, but also glycerol and urea, and aquaporin-6 - nitrates.

In the salivary glands, aquaporin-1 is localized in capillary endothelial cells, while aquaporin-3 is present in the basolateral membrane of acinar cells. The influx of water into the acinar cell leads to the integration of the aquaporin-5 protein into the apical plasma membrane, which ensures the exit of water from the cell into the salivary duct. Simultaneously, Ca 2+ ions activate ion channels in the apical membrane, and thus the outflow of water from the cell is accompanied by the release of ions into the excretory ducts. Part of the water and ions enter the composition of the primary saliva through the pericellular space. The resulting primary saliva is isotonic to blood plasma and is close to it in the composition of electrolytes (Fig. 6.2).

Rice. 6.2.Cellular mechanisms of ion transport in acinar cells.

Biosynthesis of protein secretion . In acinar cells and cells of the excretory ducts of the salivary glands, the biosynthesis of protein secretion is carried out. Amino acids enter the cell via sodium-dependent membrane transporters. Synthesis of secretory proteins occurs on ribosomes.

Ribosomes associated with the endoplasmic reticulum synthesize proteins, which are then glycosylated. The transfer of oligosaccharides to the growing polypeptide chain occurs on the inner side of the membrane of the endoplasmic reticulum. The lipid carrier is dolichol phosphate, a lipid containing about 20 isoprene residues. An oligosaccharide block consisting of 2 N-acetylglucosamine residues, 9 mannose residues, and 3 glucose residues are attached to dolichol phosphates. Its formation proceeds by successive addition of carbohydrates from UDP- and GDP-derivatives. Specific glycosyltransferases are involved in the transfer. Then the carbohydrate component is completely transferred to a certain asparagine residue of the growing polypeptide chain. In most cases, 2 out of 3 glucose residues of the attached oligosaccharide are quickly removed while the glycoprotein is still bound to the endoplasmic reticulum. When the oligosaccharide is transferred to the protein, dolichol diphosphate is released, which, under the action of phosphatase, is converted to dolichol phosphate. The synthesized initial product accumulates in the crevices and lacunae of the endoplasmic reticulum, from where it moves to the Golgi complex, where the maturation of the secret and the packaging of glycoproteins into vesicles ends (Fig. 6.3).

Fibrillar proteins and the synexin protein take part in the movement and removal of the secret from the cell. The resulting secretory granule comes into contact with the plasma membrane and a tight contact is formed. Further, intermembrane globules appear on the plasmolemma and "hybrid" membranes are formed. Holes are formed in the membrane through which the contents of the secretory granules pass into the extracellular space of the acinus. The secretory granule membrane material is then used to construct cell organelle membranes.

In the Golgi apparatus of the submandibular and sublingual salivary glands, glycoproteins are synthesized containing a large amount of sialic acids, amino sugars, which are able to bind water with the formation of mucus. These cells are characterized by a less pronounced plasma reticulum and a pronounced apparatus.

Rice. 6.3.Biosynthesis of salivary gland glycoproteins [according to Voet D., Voet J.G., 2004, as amended].

1 - formation of an oligosaccharide core in the dolichol phosphate molecule with the participation of glycosyltransferases; 2 - movement of dolichol phosphate containing oligosaccharide into the internal cavity of the endoplasmic reticulum; 3 - transfer of the oligosaccharide core to the asparagine residue of the growing polypeptide chain; 4 - release of dolichol diphosphate; 5 - recycling of dolichol phosphate.

Golgi. Synthesized glycoproteins are formed into secretory granules, which are released into the lumen of the excretory ducts.

Formation of saliva in the excretory ducts

Ductal cells synthesize and contain biologically active substances that are excreted in the apical and basolateral directions. The cells of the ducts not only form the walls of the excretory channels, but also regulate the water and mineral composition of saliva.

From the lumen of the excretory ducts, where isotonic saliva passes, Na + and Cl - ions are reabsorbed in the cell. In the cells of the striated ducts, where there are a large number of mitochondria,

Rice. 6.4.Formation of saliva in the striated cells of the excretory ducts of the salivary glands.

many molecules of CO 2 and H 2 O are formed. With the participation of carbonic anhydrase, carbonic acid dissociates into H + and HCO 3 -. Then H + ions are excreted in exchange for Na + ions, and HCO 3 - - for Cl - . On the basolateral membrane, transport proteins Na + / K + ATP-ase and Cl - are localized - a channel through which Na + and Cl - ions enter from the cell into the blood (Fig. 6.4).

The process of reabsorption is regulated by aldosterone. The flow of water in the excretory ducts is provided by aquaporins. As a result, hypotonic saliva is formed, which contains a large amount of HCO 3 - , K + ions and little Na + and Cl - .

In the course of secretion from the cells of the excretory ducts, in addition to ions, various proteins are secreted, which are also synthesized in these cells. The secretions received from the small and large salivary glands are mixed with cellular elements (leukocytes, microorganisms, desquamated epithelium), food debris, metabolites of microorganisms, which leads to the formation of mixed saliva, which is also called oral fluid.

6.3. REGULATION OF SALIVATION

The center of salivation is localized in the medulla oblongata and is controlled by the suprabulbar regions of the brain, including

nuclei of the hypothalamus and the cerebral cortex. The center of salivation is inhibited or stimulated according to the principle of unconditioned and conditioned reflexes.

Unconditional stimulators of salivation during food intake are irritations of 5 types of receptors in the oral cavity: taste, temperature, tactile, pain, olfactory.

Variation in the composition and amount of saliva is achieved by changing the excitability, number and type of excited neurons by the salivation center and, accordingly, the number and type of initiated cells of the salivary glands. The volume of salivation is determined mainly by the excitation of M-cholinergic neurons, which enhance the synthesis and secretion of acinar cells, their blood supply, and the excretion of the secret into the duct system by contractions of myoepithelial cells.

Myoepithelial cells are attached by means of semidesmosomes to the basement membrane and contain in the cytoplasm proteins-cytokeratins, smooth muscle actins, myosins, and a-actinins. Processes extend from the cell body, covering the epithelial cells of the glands. By contracting, myoepithelial cells contribute to the promotion of the secret from the terminal sections along the excretory ducts of the glands.

Acetylcholine in myoepithelial and acinar cells binds to the receptor, and activates phospholipase C through the G-protein. Phospholipase C hydrolyzes phosphatidylinositol - 4,5-bisphosphate, and the resulting inositol triphosphate increases the concentration of Ca 2+ ions inside the cell. Ca 2+ ions coming from the depot bind to the calmodulin protein. In myoepithelial cells, calcium-activated kinase phosphorylates smooth muscle myosin light chains, which interact with actin to cause them to contract (Figure 6.5). A feature of smooth muscle tissue is the rather low activity of myosin ATPase, so the slow formation and destruction of actin-myosin bridges require less ATP. In this regard, the contraction is caused slowly and is maintained for a long time.

Salivation is also regulated by sympathetic innervation, hormones and neuropeptides. The released neurotransmitters, epinephrine and norepinephrine, bind to specific adrenoreceptors on the basolateral membrane of the acinar cell. The resulting complex transmits signals through G-proteins. Activated adenylate cyclase catalyzes the transformation of the molecule

Rice. 6.5.The role of acetylcholine in the formation and secretion of secretions in the secretory sections of the salivary glands.

ATP to the second messenger 3",5" cAMP, which is accompanied by the activation of protein kinase A, followed by protein synthesis and their exocytosis from the cell. After the binding of adrenaline to a-adrenergic receptors, a molecule of 1,4,5-inositol triphosphate is formed, which is accompanied by the mobilization of Ca 2+ and the opening of calcium-dependent channels with subsequent

subsequent fluid secretion. During secretion, cells lose Ca 2+ ions, which is accompanied by a change in membrane permeability in glandular cells.

In addition to neurotransmitters (adrenaline, norepinephrine and acetylcholine), neuropeptides play an important role in the regulation of vascular tone of the salivary glands: substance P, which is a mediator of increased permeability for blood plasma proteins, and vasoactive intestinal (intestinal) polypeptide (VIP), which is involved in noncholinergic vasodilation.

The active peptides kallidin and bradykinin also affect blood flow and increase vascular permeability. Serine trypsin-like proteinase is involved in the formation of kinins - kallikrein, produced by the cells of the striated ducts. Kallikrein causes limited proteolysis of globular proteins of kininogens with the formation of biologically active peptides - kinins. Bradykinin binds to B1 and B2 receptors, which leads to the mobilization of intracellular calcium with subsequent activation of protein kinase C, which triggers a cascade of signal transmission inside the cell through nitric oxide, cGMP, and prostaglandins. The formation of these second messengers in endothelial and smooth muscle cells provides vasodilation of the salivary glands and mucous membranes. This leads to hyperemia, increased vascular permeability, lower blood pressure. The synthesis of kallikrein increases under the influence of androgens, thyroxin, prostaglandin, cholinomimetics and (3-agonists.

Aspartyl proteinase is also involved in the regulation of vascular tone - renin. Renin is concentrated in the granular convoluted ducts of the submandibular glands, where it is localized in secretory granules along with epithelial growth factor. More renin is synthesized in the salivary glands than in the kidneys. The enzyme contains two polypeptide chains linked by a disulfide bond. It is secreted as preprorenin and is activated by limited proteolysis.

Under the action of renin, angiotensinogen is cleaved and the angiotensin I peptide is released.

otensin I with an angiotensin-converting enzyme with cleavage of two amino acid residues, leads to the formation of angiotensin II, which causes narrowing of peripheral arteries, regulates water-salt metabolism and can affect the secretory function of the salivary glands (Fig. 6.6).

Rice. 6.6.Scheme of the relationship between the renin-angiotensin and kallikrein-kinin systems on the surface of the vascular endothelium in the salivary glands.

At the same time, angiotensin-converting enzyme and aminopeptidases act as kininases that cleave active kinins.

6.4. MIXED SALIVA

Mixed saliva (oral fluid) is a viscous (due to the presence of glycoproteins) liquid with a relative density of 1001-1017. Fluctuations in the pH of saliva depend on the hygienic state of the oral cavity, the nature of food, and the rate of secretion. At a low rate of secretion, the pH of saliva shifts to the acid side, and when salivation is stimulated, it shifts to the alkaline side.

Functions of mixed saliva

Digestive function . By wetting and softening solid food, saliva ensures the formation of a food bolus and facilitates

swallowing food. After impregnation with saliva, food components in the oral cavity undergo partial hydrolysis. Carbohydrates are broken down by a-amylase to dextrins and maltose, and triacylglycerols to glycerol and fatty acids by lipase secreted by the salivary glands located at the root of the tongue. The dissolution of the chemicals that make up food in saliva contributes to the perception of taste by the taste analyzer.

communicative function. Saliva is necessary for the formation of correct speech and communication. With a constant flow of air during a conversation, eating, moisture is retained in the oral cavity (mucin and other salivary glycoproteins).

Protective function . Saliva cleans the teeth and oral mucosa from bacteria and their metabolic products, food debris. The protective function is carried out by various proteins - immunoglobulins, histatins, α- and (3-defensins, cathelidine, lysozyme, lactoferrin, mucin, proteolytic enzyme inhibitors, growth factors, and other glycoproteins.

Mineralizing function . Saliva is the main source of calcium and phosphorus for tooth enamel. They enter through the acquired pellicle, which is formed from saliva proteins (statzerin, proline-rich proteins, etc.) and regulates both the entry of mineral ions into the tooth enamel and their exit from it.

Composition of mixed saliva

Mixed saliva consists of 98.5-99.5% water and dry residue (Table 6.1). The dry residue is represented by inorganic substances and organic compounds. Every day a person secretes about 1000-1200 ml of saliva. The activity of secretion and the chemical composition of saliva are subject to significant fluctuations.

The chemical composition of saliva is subject to diurnal fluctuations (circadian rhythms). The rate of salivation varies widely (0.03-2.4 ml / min) and depends on a large number of factors. During sleep, the secretion rate decreases to 0.05 ml / min, increases several times in the morning and reaches the upper limit at 12-14 hours, by 18 hours it decreases. People with low secretory activity are much more likely to develop caries, so a decrease in the amount of saliva at night contributes to the manifestation of the action of cariogenic factors. Saliva composition and secretion also depend on age and gender. In the elderly, for example, it significantly increases

Table 6.1

Chemical composition of mixed saliva

Xia amount of calcium, which is important for the formation of dental and salivary calculus. Changes in the composition of saliva can be associated with the use of drugs, intoxication and diseases. So, with dehydration, diabetes, uremia, there is a sharp decrease in salivation.

The properties of mixed saliva vary depending on the nature of the causative agent of secretion (for example, the type of food taken), the rate of secretion. So, when eating cookies, sweets in mixed saliva, the level of glucose and lactate temporarily increases. When salivation is stimulated, the amount of saliva secreted increases, the concentration of Na + and HCO 3 - ions increases in it.

Inorganic components , which are part of saliva, are represented by anions Cl -, PO 4 3-, HCO 3 -, SCN -, I -, Br -, F -, SO 4 2-, cations Na +, K +, Ca 2+, Mg 2 + and microelements: Fe, Cu, Mn, Ni, Li, Zn, Cd, Pb, Li, etc. All mineral macro- and microelements are found both in the form of simple ions and in the composition of compounds - salts, proteins and chelates (Table .6.2).

Anions HCO 3 - excreted by active transport from the parotid and submandibular salivary glands and determines the buffer capacity of saliva. The concentration of HCO 3 - saliva "rest" is 5 mmol/l, and in stimulated saliva 60 mmol/l.

Table 6.2

Inorganic components of unstimulated mixed saliva

and blood plasma

Na + and K + ions enter the mixed saliva with the secretion of the parotid and submandibular salivary glands. Saliva from the submandibular salivary glands contains 8-14 mmol/l potassium and 6-12 mmol/l sodium. Parotid saliva contains an even greater amount of potassium - about 25-49 mmol / l and much less sodium - only 2-8 mmol / l.

Saliva is oversaturated with phosphorus and calcium ions. Phosphate is found in two forms: in the form of "inorganic" phosphate and associated with proteins and other compounds. The content of total phosphate in saliva reaches 7.0 mmol / l, of which 70-95% falls on the share of inorganic phosphate (2.2-6.5 mmol / l), which is presented in the form of monohydrophosphate - HPO 4 - and dihydrogen phosphate - H 2 RO 4 - . The concentration of monohydrophosphate varies from below 1 mmol/l in saliva "rest" to 3 mmol/l in stimulated saliva. The concentration of dihydrogen phosphate in the "rest" saliva reaches 7.8 mmol/l, and in the stimulated saliva it becomes less than 1 mmol/l.

This concentration of calcium and phosphate is necessary to maintain the constancy of tooth tissues. This mechanism proceeds through three main processes: pH regulation; an obstacle in the dissolution of tooth enamel; incorporation of ions into mineralized tissues.

An increase in blood plasma to non-physiological values ​​of heavy metal ions is accompanied by their excretion through the salivary glands. Heavy metal ions that enter the oral cavity with saliva interact with hydrogen sulfide molecules released by microorganisms and metal sulfides are formed. This is how a “lead border” appears on the surface of the enamel of the teeth.

When urea is destroyed by urease of microorganisms, an ammonia molecule (NH 3) is released into the mixed saliva. Thiocyanates (SCN - , thiocyanates) enter the saliva from the blood plasma. Thiocyanites are formed from hydrocyanic acid with the participation of the enzyme rhodanese. The saliva of smokers contains 4-10 times more thiocyanate than non-smokers. Their number can also increase with inflammation of the periodontium. With the breakdown of iodothyronines in the salivary glands, iodides are released. The amount of iodides and thiocyanates depends on the rate of salivation and decreases with an increase in saliva secretion.

organic matter are represented by proteins, peptides, amino acids, carbohydrates and are mainly present in the sediment of mixed saliva formed by microorganisms, leukocytes and desquamated epithelial cells (Table 6.3). Leukocytes absorb the components of nutrients entering the oral cavity, and the resulting metabolites are released into the environment. Another part of the organic substances - urea, creatinine, hormones, peptides, growth factors, kallikrein and other enzymes - is excreted with the secretion of the salivary glands.

Lipids. The total amount of lipids in saliva is variable and does not exceed 60-70 mg/l. Most of them enter the oral cavity with the secrets of the parotid and submandibular salivary glands, and only 2% from the blood plasma and cells. Part of salivary lipids is represented by free long-chain saturated and polyunsaturated fatty acids - palmitic, stearic, eicosapentaenoic, oleic, etc. In addition to fatty acids, free cholesterol and its esters (about 28% of the total), triacylglycerols (about 40-50%) are determined in saliva. and a very small amount of glycerophospholipids. It should be noted that data on the content and nature of lipids in saliva are ambiguous.

Table 6.3

Organic components of mixed saliva

This is primarily due to the methods of purification and isolation of lipids, as well as the method of obtaining saliva, the age of the subjects and other factors.

Ureaexcreted into the oral cavity by the salivary glands. Its largest amount is secreted by the small salivary glands, then the parotid and submandibular. The amount of urea secreted depends on the rate of salivation and is inversely proportional to the amount of saliva secreted. It is known that the level of urea in saliva increases with kidney disease. In the oral cavity, urea is broken down with the participation of ureolytic bacteria in saliva sediment:

The amount of NH 3 released affects the pH of dental plaque and mixed saliva.

In addition to urea in saliva is determined uric acid, the content of which (up to 0.18 mmol / l) reflects its concentration in blood serum.

The saliva also contains creatinine in the amount of 2.0-10.0 µmol/L. All these substances determine the level of residual nitrogen in saliva.

organic acids. Saliva contains lactate, pyruvate and other organic acids, nitrates and nitrites. Saliva sediment contains 2-4 times more lactate than its liquid part, while pyruvate is determined more in the supernatant. An increase in the content of organic acids, in particular, lactate in saliva, and plaque contributes to focal demineralization of enamel and the development of caries.

Nitrates(NO s -) and nitrites(NO 2 -) enter the saliva with food, tobacco smoke and water. Nitrates with the participation of nitrate reductase of bacteria are converted into nitrites and their content depends on smoking. It has been shown that smokers and people employed in tobacco production develop leukoplakia of the oral mucosa, and nitrate reductase activity and the amount of nitrites increase in saliva. The resulting nitrites, in turn, can react with secondary amines (amino acids, drugs) to form carcinogenic nitroso compounds. This reaction takes place in an acidic environment, and it is accelerated by thiocyanates added to the reaction, the amount of which in saliva also increases when smoking.

Carbohydratesin saliva are predominantly in a protein-bound state. Free carbohydrates appear after the hydrolysis of polysaccharides and glycoproteins by glycosidases of saliva bacteria and α-amylase. However, the resulting monosaccharides (glucose, galactose, mannose, hexosamines) and sialic acids are quickly utilized by the oral microflora and converted into organic acids. Part of the glucose can come with the secretions of the salivary glands and reflect its concentration in the blood plasma. The amount of glucose in the mixed saliva does not exceed 0.06-0.17 mmol/L. The determination of glucose in saliva should be carried out by the glucose oxidase method, since the presence of other reducing substances significantly distorts the true values.

Hormones.A number of hormones, mainly of a steroid nature, are determined in saliva. They enter the saliva from the blood plasma through the salivary glands, gingival fluid, and also when taking hormones per os. Saliva contains cortisol, aldosterone, testosterone, estrogens and progesterone, as well as their metabolites. They are found in saliva mainly in the free state, and only in small amounts in combination with binding proteins. Quantity

androgens and estrogens depends on the degree of puberty and may change with the pathology of the reproductive system. The level of progesterone and estrogens in saliva, as well as in blood plasma, changes in different phases of the menstrual cycle. Normal saliva also contains insulin, free thyroxine, thyrotropin, calcitriol. The concentration of these hormones in saliva is low and does not always correlate with blood plasma levels.

Regulation of the acid-base state of the mouth

The epithelium of the oral cavity is exposed to a wide variety of both physical and chemical influences associated with eating food. Saliva is able to protect the epithelium of the upper part of the digestive tract, as well as tooth enamel. One form of protection is the preservation and maintenance of the pH environment in the oral cavity.

Since mixed saliva is a suspension of cells of a liquid medium that bathes the dentition, the acid-base state of the oral cavity is determined by the rate of salivation, the joint action of saliva buffer systems, as well as metabolites of microorganisms, the number of teeth and the frequency of their location in the dental arch. The pH value of mixed saliva normally ranges from 6.5 to 7.4 with an average value of about 7.0.

Buffer systems are such solutions that are able to maintain a constant pH environment when they are diluted or a small amount of acids or bases is added. A decrease in pH is called acidosis, and an increase is called alkalosis.

Mixed saliva contains three buffer systems: hydrocarbonate, phosphate and protein. Together, these buffer systems form the first line of defense against acidic or alkaline attack on oral tissues. All buffer systems of the oral cavity have different capacity limits: phosphate is most active at pH 6.8-7.0, hydrocarbonate at pH 6.1-6.3, and protein provides buffer capacity at various pH values.

The main buffer system of saliva is hydrocarbonate , which is a conjugated acid-base pair, consisting of a molecule H 2 CO 3 - a proton donor, and a hydrocarbonation HCO 3 - a proton acceptor.

During eating, chewing, the buffer capacity of the hydrocarbon system is provided on the basis of equilibrium: CO 2 + H 2 O \u003d HCO 3 + H +. Chewing is accompanied by an increase in salivation, which leads to an increase in

measuring the concentration of bicarbonate in saliva. When acid is added, the phase of CO 2 transition from dissolved gas to free (volatile) gas increases significantly and increases the efficiency of neutralizing reactions. Due to the fact that the end products of the reactions do not accumulate, there is a complete removal of acids. This phenomenon is called "buffer phase".

With prolonged standing of saliva, a loss of CO 2 occurs. This feature of the hydrocarbon system is called the buffering stage, and it continues until more than 50% of the hydrocarbon is used up.

After exposure to acids and alkalis, H 2 CO 3 quickly decomposes to CO 2 and H 2 O. The dissociation of carbonic acid molecules occurs in two stages:

H 2 CO 3 + H 2 O<--->HCO 3 - + H 3 O + HCO 3 - + H 2 O<--->CO 3 2- + H 3 O +

Phosphate buffer system saliva is a conjugated acid-base pair, consisting of a dihydrogen phosphate ion H 2 PO 2- (proton donor) and a monohydrophosphate ion - HPO 4 3- (proton acceptor). The phosphate system is less efficient than the hydrocarbon system and does not have the "buffer phase" effect. The concentration of HPO 4 3- in saliva is not determined by the rate of salivation, so the capacity of the phosphate buffer system does not depend on food intake or chewing.

The reactions of the components of the phosphate buffer system with acids and bases proceed as follows:

When adding acid: HPO 4 3- + H 3 O +<--->H 2 PO 2- + H 2 O

When adding a base: H 2 PO 2- + OH -<--->HPO 4 3- + H 2 O

Protein buffer system has an affinity for biological processes occurring in the oral cavity. It is represented by anionic and cationic proteins, which are highly soluble in water. This buffer system includes more than 944 different proteins, but it is not completely known which proteins are involved in the regulation of acid-base balance. Carboxyl groups of aspartate, glutamate radicals, as well as cysteine, serine and tyrosine radicals are proton donors:

R-CH 2 -COOH<--->R-CH 2 -COO - + H + (Aspartate);

R-(CH 2) 2 -COOH<--->R-CH 2 -COO - + H + (Glutamate).

The amino groups of the radicals of the amino acids histidine, lysine, arginine are able to attach protons:

R-(CH 2) 4 -NH 2 + H +<--->R-(CH 2) 4 (-N H +) (Lysine)

R-(CH 2) 3 -NH-C (= NH) -NH 2) + H +<--->(R-(CH 2) 3 -NH-C (=NH 2 +) -NH)

(arginine)

In this regard, the protein buffer system is effective at both pH 8.1 and pH 5.1.

The pH of “resting” saliva differs from the pH of stimulated saliva. Thus, the unstimulated secretion from the parotid and submandibular salivary glands has a moderately acidic pH (5.8), which increases to 7.4 with subsequent stimulation. This shift coincides with an increase in the amount of HCO 3 in saliva - up to 60 mmol/l.

Thanks to buffer systems, in practically healthy people, the pH level of mixed saliva is restored after eating to its original value within a few minutes. With the failure of buffer systems, the pH of mixed saliva decreases, which is accompanied by an increase in the rate of enamel demineralization and initiates the development of a carious process.

The pH of saliva is largely influenced by the nature of the food: when taking orange juice, coffee with sugar, strawberry yogurt, the pH drops to 3.8-5.5, while drinking beer, coffee without sugar practically does not cause changes in saliva pH .

Structural organization of saliva micelles

Why don't calcium and phosphate precipitate out? This is due to the fact that saliva is a colloidal system containing aggregates of rather small water-insoluble particles (0.1-100 nm) in suspension. There are two opposite tendencies in the colloidal system: its instability and the desire for self-strengthening and stabilization. The total value of the large surface of colloidal particles sharply increases its ability to absorb other substances by the surface layer, which increases the stability of these particles. In the case of organic colloids, along with electrolytes, which are ionic stabilizers, proteins play a stabilizing role.

A substance in a dispersed state forms an insoluble "core" of a colloidal degree of dispersion. It enters into

adsorption interaction with electrolyte ions (stabilizer) in the liquid (aqueous) phase. Stabilizer molecules dissociate in water and participate in the formation of a double electric layer around the nucleus (adsorption layer) and a diffuse layer around such a charged particle. The whole complex, consisting of a water-insoluble core, a dispersed phase, and stabilizer layers (diffuse and adsorption) covering the core, was named micelles .

What is the probable structural organization of micelles in saliva? It is assumed that the insoluble core of the micelle forms calcium phosphate [Ca 3 (PO 4) 2] (Fig. 6.7). Molecules of monohydrogen phosphate (HPO 4 2) located in saliva in excess are sorbed on the surface of the nucleus. The adsorption and diffuse layers of micelles contain Ca 2+ ions, which are counterions. Proteins (in particular, mucin), which bind a large amount of water, contribute to the distribution of the entire volume of saliva between micelles, as a result of which it becomes structured, acquires a high viscosity, and becomes inactive.

Conventions

Rice. 6.7.Suggested model of saliva micelle structure with calcium phosphate core.

In an acidic environment, the micelle charge can be halved, since monohydrogen phosphate ions bind H + protons. Dihydrogen phosphate ions appear - H 2 PO 4 - instead of HPO 4 - monohydrophosphate. This reduces the stability of the micelles, and dihydrogen phosphate ions of such micelles do not participate in the process of enamel remineralization. Alkalinization leads to an increase in phosphate ions, which combine with Ca 2+ and poorly soluble Ca 3 (PO 4) 2 compounds are formed, which are deposited in the form of tartar.

Changes in the structure of micelles in saliva also lead to the formation of stones in the ducts of the salivary glands and the development of salivary stone disease.

Microcrystallization of saliva

P.A. Leus (1977) was the first to show that structures with different structures are formed on a glass slide after drying a drop of saliva. It has been established that the nature of saliva microcrystals has individual characteristics, which can be associated with the state of the body, oral tissues, the nature of nutrition and the ecological situation.

When the saliva of a healthy person is dried under a microscope, microcrystals are visible that have a characteristic pattern of formed "fern leaves" or "coral branches" (Fig. 6.8).

There is a certain dependence of the type of pattern on the degree of saliva viscosity. At low viscosity, microcrystals are represented by small, shapeless, scattered, sparsely located formations without a clear structure. They include separate sections in the form of thin, weakly expressed "fern leaves" (Fig. 6.9, A). On the contrary, at high viscosity of the mixed saliva, the microcrystals are densely arranged and mostly chaotically oriented. There are a large number of granular and diamond-shaped structures of a darker color compared to similar formations found in mixed saliva with normal viscosity (Fig. 6.9, B).

The use of water saturated with minerals with high electrical conductivity (coral water) normalizes the viscosity and restores the structure of liquid crystals in the oral fluid.

The nature of the pattern of microcrystals also changes with the pathology of the dentoalveolar system. So for the compensated form of the course of caries, a clear pattern of elongated crystals is characteristic.

Rice. 6.8.The structure of microcrystals of saliva of a healthy person.

Rice. 6.9.The structure of microcrystals of mixed saliva:

BUT- low viscosity saliva; B- saliva of increased viscosity.

loprismatic structures fused with each other and occupying the entire surface of the drop. With a subcompensated form of caries flow, individual dendritic crystal-prismatic structures of small sizes are visible in the center of the drop. With a decompensated form of caries, a large number of isometrically arranged crystalline structures of irregular shape are visible over the entire area of ​​the drop.

On the other hand, there is evidence that microcrystallization of saliva reflects the state of the organism as a whole; therefore, it is proposed to use the crystallization of saliva as a test system for the rapid diagnosis of certain somatic diseases or a general assessment of the state of the body.

Saliva proteins

Currently, about 1009 proteins have been detected in mixed saliva by two-dimensional electrophoresis, of which 306 have been identified.

Most saliva proteins are glycoproteins, in which the amount of carbohydrates reaches 4-40%. The secretions of various salivary glands contain glycoproteins in different proportions, which determines the difference in their viscosity. Thus, the most viscous saliva is the secret of the sublingual gland (viscosity coefficient 13.4), then submandibular (3.4) and parotid (1.5). Under conditions of stimulation, defective glycoproteins can be synthesized and saliva becomes less viscous.

Salivary glycoproteins are heterogeneous and differ in mol. mass, mobility in the isoelectric field and phosphate content. Oligosaccharide chains in salivary proteins bind to the hydroxyl group of serine and threonine with an O-glycosidic bond or attach to an asparagine residue through an N-glycosidic bond (Fig. 6.10).

Sources of proteins in mixed saliva are:

1. Secrets of the major and minor salivary glands;

2. Cells - microorganisms, leukocytes, desquamated epithelium;

3. Blood plasma. Saliva proteins perform many functions (Fig. 6.11). Wherein

the same protein can be involved in several processes, which allows us to speak about the polyfunctionality of salivary proteins.

secretory proteins . A number of saliva proteins are synthesized by the salivary glands and are represented by mucin (two isoforms M-1, M-2), proteins rich in proline, immunoglobulins (IgA, IgG, IgM),

Rice. 6.10.Attachment of monosaccharide residues in glycoproteins through O- and N-glycosidic bonds.

kallikrein, parotin; enzymes - a-amylase, lysozyme, histatins, cystatins, statzerin, carbonic anhydrase, peroxidase, lactoferrin, proteinases, lipase, phosphatases and others. They have a different pier. mass; mucins and secretory immunoglobulin A have the greatest (Fig. 6.12). These saliva proteins form a pellicle on the oral mucosa, which provides lubrication, protects the mucosa from environmental factors and proteolytic enzymes secreted by bacteria and destroyed polymorphonuclear leukocytes, and also prevents its drying.

Mucins -high molecular weight proteins with many functions. Two isoforms of this protein were found, which differ in mol. mass: mucin-1 - 250 kDa, mucin-2 - 1000 kDa. Mucin is synthesized in the submandibular, sublingual and minor salivary glands. The mucin polypeptide chain contains a large amount of serine and threonine, and there are about 200 of them in total.

Rice. 6.11.Polyfunctionality of mixed saliva proteins.

Rice. 6.12.Molecular weight of some major secretory proteins of saliva [according to Levine M., 1993].

one polypeptide chain. The third most common amino acid in mucin is proline. N-acetyl-

neuraminic acid, N-acetylgalactosamine, fructose and galactose. The protein itself resembles a comb in its structure: short carbohydrate chains stick out like teeth from a tough, proline-rich, polypeptide backbone (Fig. 6.13).

Due to the ability to bind a large amount of water, mucins add viscosity to saliva, protect the surface from bacterial contamination and the dissolution of calcium phosphate. Bacterial protection is provided in conjunction with immunoglobulins and some other proteins attached to the mucin. Mucins are present not only in saliva, but also in the secretions of the bronchi and intestines, seminal fluid and secretions from the cervix, where they play the role of lubricant and protect the underlying tissues from chemical and mechanical damage.

Oligosaccharides associated with mucins have antigenic specificity, which corresponds to group-specific antigens, which are also present as sphingolipids and glycoproteins on the surface of erythrocytes and as oligosaccharides in milk and urine. The ability to secrete group-specific substances in saliva is inherited.

The concentration of group-specific substances in saliva is 10-130 mg/l. They mainly come from the secretion of small salivary glands and correspond exactly to the blood type. The study of group-specific substances in saliva is used in forensic medicine to establish

Rice. 6.13.The structure of salivary mucin.

changes in the blood group in cases where it cannot be done otherwise. In 20% of cases, there are individuals in whom the glycoproteins contained in the secrets are devoid of the characteristic antigenic specificity A, B or H.

Proteins rich in proline (BBP). These proteins were first reported in 1971 by Oppenheimer. They were discovered in the saliva of the parotid glands and account for up to 70% of the total amount of all proteins in this secret. Mol. the BBP mass ranges from 6 to 12 kDa. A study of the amino acid composition revealed that 75% of the total number of amino acids are proline, glycine, glutamic and aspartic acids. This family is united by several proteins, which are divided into 3 groups according to their properties: acidic BBP; basic BBP; glycosylated BBP.

BBPs perform several functions in the oral cavity. First of all, they are easily adsorbed on the enamel surface and are components of the acquired tooth pellicle. Acidic BBP, which are part of the tooth pellicle, bind to the protein staterin and prevent its interaction with hydroxyapatite at acidic pH values. Thus, acidic BBPs delay the demineralization of tooth enamel and inhibit excessive deposition of minerals, that is, they maintain a constant amount of calcium and phosphorus in tooth enamel. Acidic and glycosylated BBPs are also able to bind certain microorganisms and thus participate in the formation of microbial colonies in dental plaque. Glycosylated BBPs are involved in the wetting of the food bolus. It is assumed that the main BBPs play a certain role in the binding of food tannins and thereby protect the oral mucosa from their damaging effects, and also impart viscoelastic properties to saliva.

Antimicrobial peptides they enter mixed saliva with the secretion of the salivary glands from leukocytes and the epithelium of the mucous membrane. They are represented by cathelidines; α - and (3-defensins; calprotectin; peptides with a high proportion of specific amino acids (histatins).

Histatins(proteins rich in histidine). From the secretions of the parotid and submandibular human salivary glands, a family of basic oligo- and polypeptides, characterized by a high content of histidine, has been isolated. The study of the primary structure of histatins showed that they consist of 7-38 amino acid residues and have a high degree of similarity with each other. The family of histatins is represented by 12 pep-

tidy with different mol. mass. It is believed that individual peptides of this family are formed in reactions of limited proteolysis, either in secretory vesicles or during the passage of proteins through the glandular ducts. Histatins -1 and -2 are significantly different from other members of this family of proteins. It has been established that histatin-2 is a fragment of histatin-1, and histatins-4-12 are formed during the hydrolysis of histatin-3 with the participation of a number of proteinases, in particular, kallikrein.

Although the biological functions of histatins have not been fully elucidated, it has already been established that histatin-1 is involved in the formation of the acquired tooth pellicle and is a potent inhibitor of the growth of hydroxyapatite crystals in saliva. A mixture of purified histatins inhibits the growth of some types of streptococci (Str. mutans). Histatin-5 inhibits the action of the immunodeficiency virus and fungi (Candida albicans). One of the mechanisms of such antimicrobial and antiviral action is the interaction of histatin-5 with various proteinases isolated from oral microorganisms. It has also been shown that they bind to specific fungal receptors and form channels in their membrane, which ensures the transport of K + , Mg 2+ ions into the cell with the mobilization of ATP from the cell. Mitochondria are also targets for histatins in microbial cells.

α- and ^-Defensins - low molecular weight peptides with a mol. weighing 3-5 kDa, having (3-structure and rich in cysteine. The source of α-defensins are leukocytes, and (3-defensins - keratinocytes and salivary glands. Defensins act on gram-positive and gram-negative bacteria, fungi (Candida albicans) and some viruses. They form ion channels depending on the cell type, and also aggregate with membrane peptides and thus ensure the transport of ions through the membrane. Defensins also inhibit protein synthesis in bacterial cells.

Protein is also involved in antimicrobial defense calprotectin - a peptide that has a powerful antimicrobial effect and enters the saliva from epitheliocytes and neutrophilic granulocytes.

Staterins(proteins rich in tyrosine). Phosphoproteins containing up to 15% proline and 25% acidic amino acids have been isolated from the secretion of the parotid salivary glands, they say. whose mass is 5.38 kDa. Together with other secretory proteins, they inhibit the spontaneous precipitation of calcium phosphorus salts on the surface of the tooth, in the oral cavity and in the salivary glands. Staterins bind Ca 2+ , inhibiting its deposition and formation of hydroxyapatites in saliva. Also, these proteins have the ability not only to inhibit the growth of crystals, but also the nucleation phase (formation of the seed of the future crystal). They are determined in the enamel pellicle and are associated by the N-terminal region with enamel hydroxyapatites. Statherins together with histatins inhibit the growth of aerobic and anaerobic bacteria.

lactoferrin- a glycoprotein contained in many secrets. It is especially abundant in colostrum and saliva. It binds iron (Fe 3+) of bacteria and disrupts redox processes in bacterial cells, thereby exerting a bacteriostatic effect.

Immunoglobulins . Immunoglobulins are divided into classes depending on the structure, properties and antigenic features of their heavy polypeptide chains. All 5 classes of immunoglobulins are present in saliva - IgA, IgAs, IgG, IgM, IgE. The main oral immunoglobulin (90%) is secretory immunoglobulin A (SIgA, IgA 2), which is secreted by the parotid salivary glands. The remaining 10% of IgA 2 are secreted by the minor and submandibular salivary glands. Whole saliva in adults contains 30 to 160 µg/mL of SIgA. IgA 2 deficiency occurs in one case per 500 people and is accompanied by frequent viral infections. All other types of immunoglobulins (IgE, IgG, IgM) are determined in smaller quantities. They come from the blood plasma by simple extravasation through the minor salivary glands and the periodontal sulcus.

Leptin- protein with a mol. with a mass of 16 kDa participates in the processes of regeneration of the mucous membrane. By binding to keratinocyte receptors, it causes the expression of keratinocyte and epithelial growth factors. Through phosphorylation of the STAT-1 and STAT-3 signaling proteins, these growth factors promote keratinocyte differentiation.

Glycoprotein 340(gp340, GP 340) is a protein rich in cysteine, with a pier. weighing 340 kDa; refers to antiviral proteins. Being an agglutinin, GP 340 in the presence of Ca 2+ binds to adenoviruses and viruses that cause hepatitis and HIV infection. He is also mutually

works with oral bacteria (Str. mutans, Helicobacter pylori and etc.) and suppresses their cohesion during the formation of colonies. Inhibits the activity of leukocyte elastase and thus protects saliva proteins from proteolysis.

Specific proteins were also found in saliva - salivoprotein, which promotes the deposition of phosphorus-calcium compounds on the surface of tooth enamel, and phosphoprotein, a calcium-binding protein with a high affinity for hydroxyapatite, which is involved in the formation of tartar and plaque.

In addition to secretory proteins, albumins and globulin fractions enter the mixed saliva from the blood plasma.

saliva enzymes. The leading role among the protective factors of saliva is played by enzymes of various origins - a-amylase, lysozyme, nucleases, peroxidase, carbonic anhydrase, etc. To a lesser extent, this applies to amylase, the main enzyme of mixed saliva involved in the initial stages of digestion.

Glycosidases.In saliva, the activity of endo- and exoglycosidases is determined. Salivary a-amylase primarily belongs to endoglycosidases.

α-amylase.Salivary α-amylase cleaves α(1-4)-glycosidic bonds in starch and glycogen. In its immunochemical properties and amino acid composition, salivary α-amylase is identical to pancreatic amylase. Certain differences between these amylases are due to the fact that salivary and pancreatic amylases are encoded by different genes (AMU 1 and AMU 2).

Isoenzymes of a-amylase are represented by 11 proteins, which are combined into 2 families: A and B. Proteins of the A family have a mol. mass of 62 kDa and contain residues of carbohydrates, and isoenzymes of the B family are devoid of a carbohydrate component and have a lower mol. mass - 56 kDa. In mixed saliva, an enzyme was identified that cleaves off the carbohydrate component and by deglycosylation of isoamylases, and family A proteins are converted into family B proteins.

α-Amylase is excreted with the secretion of the parotid gland and labial small glands, where its concentration is 648-803 μg / ml and is not associated with age, but varies during the day depending on brushing your teeth and eating.

In addition to a-amylase, the activity of several more glycosidases is determined in mixed saliva - a-L-fucosidase, a- and (3-glucosidase, a- and (3-galactosidases, a-D-mannosidases, (3-glucuronidases, (3-hyaluronidases, β-N-acetylhexosaminidase, neuraminidase. All of them

have different origins and different properties. α-L-Fucosidase is secreted with the secretion of the parotid salivary glands and cleaves α-(1-»2) glycosidic bonds in short oligosaccharide chains. The source of β-N-D-acetylhexosaminidase in mixed saliva is the secrets of the large salivary glands, as well as the microflora of the oral cavity.

α- and (3-glucosidases, α- and (3-galactosidases, (3-glucuronidase, neuraminidase, and hyaluronidase) are of bacterial origin and are most active in an acidic environment. correlates with the number of gram-negative bacteria and increases with inflammation of the gums.Together with hyaluronidase activity, the activity of (3-glucuronidase) increases, which is normally suppressed by the inhibitor of (3-glucocuronidase, coming from the blood plasma.

It was shown that despite the high activity of acid glycosidases in saliva, these enzymes are able to cleave glycosidic chains in salivary mucins with the formation of sialic acids and amino sugars.

Lysozyme -protein with mol. weighing about 14 kDa, the polypeptide chain of which consists of 129 amino acid residues and is folded into a compact globule. The three-dimensional conformation of the polypeptide chain is supported by 4 disulfide bonds. The lysozyme globule consists of two parts: one contains amino acids with hydrophobic groups (leucine, isoleucine, tryptophan), the other part is dominated by amino acids with polar groups (lysine, arginine, aspartic acid).

The salivary glands are the source of lysozyme in the oral fluid. Lysozyme is synthesized by the epithelial cells of the ducts of the salivary glands. With mixed saliva, approximately 5.2 μg of lysozyme enters the oral cavity per 1 minute. Another source of lysozyme is neutrophils. The bactericidal action of lysozyme is based on the fact that it catalyzes the hydrolysis of the α (1-4) -glycosidic bond connecting N-acetylglucosamine with N-acetylmuramic acid in the polysaccharides of the cell wall of microorganisms, which contributes to the destruction of murein in the bacterial cell wall (Fig. 6.14).

When the hexasaccharide fragment of murein is placed in the active center of the lysozyme macromolecule, all monosaccharide units retain the chair conformation, except for ring 4, which falls into too

Rice. 6.14.Structural formula of murein present in the membrane of Gram-positive bacteria.

com is closely surrounded by side radicals of amino acid residues. Ring 4 assumes a more tense half-chair conformation and flattens out. The glycosidic bond between rings 4 and 5 is located in close proximity to the amino acid residues of the active center asp-52 and glu-35, which are actively involved in its hydrolysis (Fig. 6.15).

Through hydrolytic cleavage of the glycosidic bond in the polysaccharide chain of murein, the bacterial cell wall is destroyed, which forms the chemical basis of the antibacterial action of lysozyme.

Gram-positive microorganisms and some viruses are most sensitive to lysozyme. The formation of lysozyme is reduced in certain types of oral diseases (stomatitis, gingivitis, periodontitis).

carbonic anhydrase- an enzyme belonging to the class of lyases. Catalyzes the cleavage of the C-O bond in carbonic acid, which leads to the formation of CO 2 and H 2 O molecules.

Type VI carbonic anhydrase is synthesized in the acinar cells of the parotid and submandibular salivary glands and secreted into saliva as part of secretory granules. This is a protein with a pier. weighing 42 kDa and is about 3% of the total amount of all proteins in parotid saliva.

The secretion of carbonic anhydrase VI into saliva follows a circadian rhythm: its concentration is very low during sleep and rises during the daytime after waking up and eating breakfast. This circadian addiction is very similar

Rice. 6.15.Hydrolysis (3 (1-> 4) a glycosidic bond in murein by the enzyme lysozyme.

with salivary β-amylase and proves a positive correlation between the level of salivary amylase activity and the concentration of carbonic anhydrase VI. This proves that these two enzymes are secreted by similar mechanisms and may be present in the same secretory granules. Carbanhydrase regulates the buffer capacity of saliva. Recent studies have shown that carbonic anhydrase VI binds to the enamel pellicle and retains its enzymatic activity on the tooth surface. On the pellicle, carbonic anhydrase VI is involved in the conversion of bicarbonate and metabolic products of bacteria into CO 2 and H 2 O. Accelerating the removal of acids from the tooth surface, carbonic anhydrase VI protects tooth enamel from demineralization. A low concentration of carbonic anhydrase VI in saliva is found in people with an active carious process.

Peroxidasesbelong to the class of oxidoreductases and catalyze the oxidation of the H2O2 donor. The latter is formed in the oral cavity by a microorganism

mami and its amount depends on the metabolism of sucrose and amino sugars. The enzyme superoxide dismutase catalyzes the formation of H 2 O 2 (Fig. 6.16).

Rice. 6.16.Superoxide anion dismutation reaction by the enzyme superoxide dismutase.

The salivary glands secrete thiocyanate ions (SCN -), Cl - , I - , Br - into the oral cavity. In mixed saliva, salivary peroxidase (lactoperoxidase) and myeloperoxidase are normally present, and glutathione peroxidase appears in pathological conditions.

Salivary peroxidase refers to hemoproteins and is formed in the acinar cells of the parotid and submandibular salivary glands. It is represented by multiple forms with a pier. weighing 78, 80 and 28 kDa. In the secret of the parotid gland, the activity of the enzyme is 3 times higher than in the submandibular. Salivary peroxidase oxidizes SCN - thiocyanates. The mechanism of SCN oxidation - includes several reactions (Fig. 6.17). The greatest oxidation of SCN - salivary peroxidase occurs at pH 5.0-6.0, so the antibacterial effect of this enzyme increases at acidic pH values. The resulting hypothiocyanate (-OSCN) at pH<7,0 подавляет рост Str. mutans and has 10 times more powerful antibacterial action

thinner than H 2 O 2 . At the same time, with a decrease in pH, the risk of demineralization of hard dental tissues increases.

In the process of purification and isolation of salivary peroxidase, it was found that the enzyme is in a complex with one of the BBPs, which, apparently, allows this enzyme to participate in the protection of tooth enamel from damage.

Myeloperoxidase is released from polymorphonuclear leukocytes, which oxidizes ions Cl - , I - , Br - . The result of the interaction of the system "hydrogen peroxide-chlorine" is the formation of hypochlorite

Rice. 6.17.Stages of oxidation of thiocyanates by salivary peroxidase.

(HOCl-). The object of action of the latter is the amino acids of the proteins of microorganisms, which are converted into active aldehydes or other toxic products. In this regard, the ability of the salivary glands, along with peroxidase, to excrete significant amounts of ions SCN - , Cl - , I - , Br - . B should also be attributed to the function of antimicrobial protection.

Thus, the biological role of peroxidases present in saliva is that, on the one hand, the oxidation products of thiocyanates and halogens inhibit the growth and metabolism of lactobacilli and some other microorganisms, and on the other hand, the accumulation of H 2 O 2 molecules by many species is prevented. streptococci and cells of the oral mucosa.

Proteinases(salivary proteolytic enzymes). In saliva, there are no conditions for the active breakdown of proteins. This is due to the fact that there are no denaturing factors in the oral cavity, and there are also a large number of inhibitors of proteinases of a protein nature. The low activity of proteinases allows salivary proteins to remain in their native state and fully perform their functions.

In the saliva of a healthy person, a low activity of acidic and weakly alkaline proteinases is determined. The source of proteolytic enzymes in saliva are predominantly microorganisms and leukocytes. Trypsin-like, aspartyl, serine and matrix metalloproteinases are present in saliva.

Trypsin-like proteinases cleave peptide bonds, in the formation of which the carboxyl groups of lysine and arginine take part. Among weakly alkaline trypsin-like proteinases, kallikrein is the most active in mixed saliva.

Acid trypsin-like cathepsin B is practically not detected in the norm and its activity increases during inflammation. Cathepsin D, an acid proteinase of lysosomal origin, is distinguished by the fact that there is no inhibitor specific for it in the body and in the oral cavity. Cathepsin D is released from leukocytes as well as from inflamed cells, so its activity is increased in gingivitis and periodontitis. Matrix metalloproteinases in saliva appear when the intercellular matrix of periodontal tissues is destroyed, and their source is gingival fluid and cells.

Protein inhibitors of proteinases . The salivary glands are the source of a large number of secretory proteinase inhibitors.

They are represented by cystatins and low molecular weight acid-stable proteins.

Acid-stable protein inhibitors withstand heating up to 90°C at acidic pH values ​​without losing their activity. These are low molecular weight proteins with a mol. weighing 6.5-10 kDa, capable of inhibiting the activity of kallikrein, trypsin, elastase and cathepsin G.

Cystatins.In 1984, two groups of Japanese researchers independently reported the presence in saliva of yet another group of secretory proteins, salivary cystatins. Salivary cystatins are synthesized in the serous cells of the parotid and submandibular salivary glands. These are acidic proteins with a pier. weighing 9.5-13 kDa. A total of 8 salivary cystatins were found, of which 6 proteins were characterized (cystatin S, an extended form of cystatin S-HSP-12, SA, SN, SAI, SAIII). Salivary cystatins inhibit the activity of trypsin-like proteinases - cathepsins B, H, L, G, in the active center of which there is a residue of the amino acid cysteine.

Cystatins SA, SAIII are involved in the formation of the acquired pellicle of the teeth. Cystatin SA-III contains 4 phosphoserine residues that are involved in binding to tooth enamel hydroxyapatites. The high degree of adhesion of these proteins is probably due to the fact that cystatins are similar in amino acid sequence to other adhesive proteins, fibronectin and laminin.

It is believed that salivary cystatins perform antimicrobial and antiviral functions through inhibition of the activity of cysteine ​​proteinases. They also protect salivary proteins from enzymatic degradation, since secretory proteins can only function in an intact state.

α1 - proteinase inhibitor (α 1 -antitrypsin) and α2 -macroglobulin (α2 -M) enter mixed human saliva from blood plasma. α 1 -Antitrypsin is determined only in one third of the studied saliva samples. It is a single chain protein of 294 amino acid residues, which is synthesized in the liver. It competitively inhibits microbial and leukocyte serine proteinases, elastase, collagenase, as well as plasmin and kallikrein.

α2 -Macroglobulin - a glycoprotein with a mol. weighing 725 kDa, consisting of 4 subunits and capable of inhibiting any proteinases (Fig. 6.18). It is synthesized in the liver and in saliva is determined only in 10% of the examined healthy people.

Rice. 6.18.Scheme of the mechanism of inhibition of proteinase α 2 -macroglobulin: BUT - active proteinase binds to a certain part of the α 2 -macroglobulin molecule and an unstable complex α 2 -macroglobulin - proteinase is formed; B - the enzyme cleaves a specific peptide bond (“bait”), which leads to conformational changes in the α 2 -macroglobulin protein molecule; AT - proteinase covalently binds to a site in the α 2 -macroglobulin molecule, which is accompanied by the formation of a more compact structure. The resulting complex with the current of saliva is removed into the gastrointestinal tract.

In mixed saliva, most protein inhibitors of proteinases are in complex with proteolytic enzymes, and only a small amount is in the free state. During inflammation, the amount of free inhibitors in saliva decreases, and the inhibitors in the complexes undergo partial proteolysis and lose their activity.

Since the salivary glands are a source of proteinase inhibitors, they are used for the preparation of drugs (Trasilol, Kontrykal, Gordoks, etc.).

Nucleases (RNases and DNases) play an important role in the implementation of the protective function of mixed saliva. The main source of them in saliva are leukocytes. In mixed saliva, acidic and alkaline RNases and DNases, which differ in different properties, were found. Experiments have shown that these enzymes dramatically slow down the growth and reproduction of many microorganisms in the oral cavity. In some inflammatory diseases of the soft tissues of the oral cavity, their number increases.

Phosphatases- enzymes of the hydrolase class, which cleave inorganic phosphate from organic compounds. In saliva, they are represented by acid and alkaline phosphatases.

Acid phosphatase (pH 4.8) is contained in lysosomes and enters the mixed saliva with the secrets of the large salivary glands, and

also from bacteria, leukocytes and epithelial cells. In saliva, up to 4 isoenzymes of acid phosphatase are determined. Enzyme activity in saliva tends to be increased in periodontitis and gingivitis. There are conflicting reports on changes in the activity of this enzyme in dental caries. Alkaline phosphatase(pH 9.1-10.5). In the secretions of the salivary glands of a healthy person, the activity of alkaline phosphatase is low and its origin in mixed saliva is associated with cellular elements. The activity of this enzyme, as well as acid phosphatase, increases with inflammation of the soft tissues of the oral cavity and caries. At the same time, the obtained data on the activity of this enzyme are very contradictory and do not always fit into a definite pattern.

6.5. SALIVADIAGNOSTICS

The study of saliva refers to non-invasive methods and is carried out to assess the age and physiological status, identify somatic diseases, pathology of the salivary glands and oral tissues, genetic markers, and monitor drugs.

With the advent of new quantitative methods for laboratory

research is increasingly using mixed saliva. advantage

of such methods compared with the study of blood plasma are:

Non-invasive collection of saliva, making it convenient to receive as

in adults and children; lack of stress in the patient during the procedure for obtaining saliva; the ability to use simple tools and fixtures

to receive saliva; there is no need for the presence of a doctor and paramedical personnel during the collection of saliva; there is a possibility of repeated and repeated obtaining of material for research; saliva can be stored in the cold for a certain time before testing. Unstimulated mixed saliva is obtained by spitting after rinsing the mouth. The saliva of the large salivary glands is collected by catheterization of their ducts and collected in Leshli-Krasnogorsky capsules fixed to the oral mucosa above

ducts of the parotid, submandibular and sublingual salivary glands. Under the influence of stimulants of salivary secretion (chewing food, paraffin, applying sour and sweet substances to the taste buds of the tongue), stimulated saliva is formed. In the saliva released over a certain time, taking into account its volume, the viscosity, pH, content of electrolytes, enzymes, mucin and other proteins and peptides are determined.

To assess the functional state of the salivary glands, it is necessary to measure the amount of stimulated and unstimulated saliva secreted over a certain time; then calculate the rate of secretion in ml/min. A decrease in the amount of saliva secreted is accompanied by a change in its composition and is observed during stress, dehydration, during sleep, anesthesia, in old age, with renal failure, diabetes mellitus, hypothyroidism, mental disorders, Sjogren's disease, salivary stone disease. A significant decrease in the amount of saliva leads to the development of dryness in the oral cavity - xerostomia. Increased secretion (hypersalivation) is observed during pregnancy, hyperthyroidism, inflammatory diseases of the oral mucosa.

The quantitative and qualitative composition of saliva depends on the physiological status and age; for example, the saliva of infants up to 6 months contains 2 times more Na + ions compared to the saliva of an adult, which is associated with reabsorption processes in the salivary glands. With age, the amount of IgA, thiocyanates, and rapidly migrating forms of amylase isoenzymes increases in saliva.

Saliva is a source of genetic markers. According to protein polymorphism, the presence of water-soluble glycoproteins with antigenic specificity reflects the number of loci and alleles, as well as the frequency of alleles in different human races, which is of great importance in anthropology, population genetics, and forensic medicine.

Measuring the concentration of hormones in saliva makes it possible to assess the state of the adrenal glands, gonadotropic function, the rhythms of the formation and release of hormones. Saliva is examined to assess the metabolism of drugs, for example, ethanol, phenobarbital, lithium preparations, salicylates, diazepam, etc. At the same time, a correlation between the quantitative series of drugs in the blood and saliva does not always exist, which makes it difficult to use saliva in drug monitoring.

Certain shifts in the composition of both mixed saliva and from the ducts are detected in various somatic diseases. So, with uremia that occurs with renal failure, both in saliva and in blood serum, the amount of urea and creatinine increases. With arterial hypertension in the parotid saliva, the level of cAMP, total calcium, K + ions increases, but the concentration of Ca 2+ ions decreases. With polycystic testis accompanied by infertility, the concentration of free testosterone in saliva increases, and with damage to the adrenal glands and the use of cortisol in replacement therapy, the content of 17 α-hydroxytestosterone in saliva increases. In patients with hypofunction of the pituitary gland, bronze disease, the determination of cortisol in saliva is more informative than in urine and saliva. Stress is also characterized by an increase in the amount of cortisol. The concentration of cortisol in saliva has a circadian rhythm and depends on the psycho-emotional state. In early pregnancy and in liver cancer, chorionic gonadotropin appears in saliva. With tumors of the thyroid gland in saliva, the concentration of thyroglobulin increases; in acute pancreatitis, the amount of pancreatic and salivary α-amylase and lipase increases. In patients with hypothyroidism, the concentration of thyroxine and triiodothyronine in saliva is almost halved, and thyrotropin (TSH) is 2.8 times higher than in healthy individuals.

Changes in the composition of saliva are observed when the salivary glands are affected. In chronic parotitis, the extravasation of serum proteins, in particular, albumin, increases, the secretion of kallikrein, lysozyme increases; their number increases during the period of exacerbation. With tumors of the glands, not only the amount of secretion changes, but additional protein fractions appear in saliva, mainly of serum origin. Sjögren's syndrome is characterized by a decrease in salivation and salivation, which is associated with inhibition of the functions of aquaporin transport proteins. Water transport from acinar cells is reduced, which leads to cell swelling and damage. In the saliva of these patients, the amount of IgA and IgM, the activity of acid proteinases and acid phosphatase, lactoferrin and lysozyme increase; the content of Na + , Cl - , Ca 2+ and PO 4 3- ions changes.

Although no significant deviations were found in the composition of saliva during caries (and this information is extremely contradictory), it is nevertheless shown that in caries-resistant individuals, the content of amylase is significantly

higher than in those susceptible to caries. There is also evidence that during caries, the activity of acid phosphatase increases, the number of (3-defensins) decreases, the activity of lactate dehydrogenase changes, the pH of saliva and the rate of salivation decrease.

Inflammation of the periodontium is accompanied by an increase in the activity of cathepsins D and B and weakly alkaline proteinases in saliva. At the same time, free antitriptic activity decreases, but the activity of locally produced acid-stable proteinase inhibitors increases by 1.5 times, most of which are in complex with proteinases. The properties of the acid-stable inhibitors themselves also change, which is associated with the formation of their partially cleaved forms under the action of various proteinases. In saliva, the activity of ALT and AST increases. Periodontitis is characterized by an increase in the activity of hyaluronidase (3-glucuronidase and its inhibitor. The activity of peroxidase increases by 1.5-1.6 times, and the content of lysozyme decreases by 20-40%. Changes in the defense system are combined with an increase in the amount of thiocyanates by 2-3 The content of immunoglobulins varies ambiguously, but the amount of plasma IgG and IgM always increases.

With periodontal inflammation and pathology of the oral mucosa, free radical oxidation is activated, which is characterized by an increase in the amount of malondialdehyde in saliva and an increase in superoxide dismutase activity. Glutathione peroxidase enters the saliva from the blood plasma during bleeding gums, as well as through the gingival fluid, the activity of which is not normally determined.

With periodontitis, the activity of nitrate reductase and the content of nitrites also change. With mild and moderate severity of periodontitis, the activity of nitrate reductase decreases, however, with an exacerbation of the process in severe periodontitis, the activity of the enzyme doubles compared to the norm, and the amount of nitrites decreases by 4 times.