SURFACTANT (from English surface active agents surfactants; synonym: anti-atelectatic factor, surface-active factor) — the complex substance of the lipidic and proteinaceous and carbohydrate nature which is located in the form of a film on the interphase boundary air — liquid in alveoluses of lungs and the regulating surface intention at change of their volume. The main fiziol. S.'s role consists in maintenance of stability of alveolar structure lungs (see) by decrease in surface intention in alveoluses at reduction of their volume on an exhalation. The page participates in exchange of gases and liquid through an aerogematichesky barrier, removal of foreign debris from a surface of alveoluses, protection of elements of a wall of alveoluses against the damaging action of oxidizers and peroxides, and also as assume, in immune responses.
S.'s structure, its functions, value in pathology remain insufficiently clear and are a subject of discussions. Idea of S. as lamellar is most proved or to a net, edges consists of bilipidny membranes and includes lipoproteidny and glikoproteidny complexes. Membranes of osmiofilny lamellar little bodies of the alveolotsit synthesizing and cosecreting surfactants have a similar structure. The main chemical component C. are phospholipids, from to-rykh the most expressed superficial activity the fraction of saturated phosphatidylsincaline (lecithin) — dipalmitylphosphatidylsincaline possesses; besides, fractions of phosphatidylethanolamine, phosphatidylglycerin, phosphatidylserine, a lizofosfatidilkholin, sphingomyelin, phosphatidylinositol, fosfatidny and lizodifosfatidny to - t are allocated. Also triglycerides, cholesterol, serumal (albumine, immunoglobulins, etc.) and specific not serumal (apoproteins C.) proteins, carbohydrates are S.'s part (glucose, a galactose, a fukoza, glikozaminoglikana, etc.).
Various exogenous and internal causes can have the damaging effect on S.: disturbance of partial pressure of oxygen in inhaled air, air pollution, microorganisms, anesthetics, disturbances of a hemodynamics, ventilation, an innervation and metabolism in lungs at diseases of lungs and hearts, operative measures, etc.
Many patol. processes in lungs (hypostasis, hemorrhages, an atelectasis, a vascular embolism) are followed by decrease in superficial activity of Page. S.'s changes are found in the centers of pneumonia, a pneumosclerosis, tuberculosis, at emphysema of lungs. However in most cases the causal relationship of disturbances of properties C. with a certain type of defeat, as well as a role of changes of S. in development of this or that patol is finally not found out. conditions of lungs. A setpoint value of deficit of S. in a pathogeny of inborn atelectasis (see), a hyaline and membrane disease of newborns (see) and other pneumopathies of the newborns who are clinically shown respiratory distress syndrome (see). Reduction of activity of S. is considered as one of mechanisms of development of a focal atelectasis, hypostasis and hyaline membranes at respiratory insufficiency at adults.
Villages study with the help morfol. methods, hl. obr. a submicroscopy (see) tissues of lungs, and also by physical. - chemical and biochemical researches of endobronchial washouts, aspirates, extracts from tissue of lungs, from a trachea and a throat, an amniotic fluid. The chemical structure of S. is studied by means of the standard methods. Results of a research C. found application in clinic for development of diagnostic tests of antenatal assessment of risk of development a distress syndrome (e.g., definition of the quantitative relation of lecithin to sphingomyelin in an amniotic fluid, the sheyk-test), forecasting of an outcome of this syndrome, research of prophylactics and treatment of respiratory insufficiency (see).
Bibliography: Berezovsky V. A. and Gorchakov V. Yu. Surfactants of a lung, Kiev, 1982, bibliogr.; Birkun A. A., Nesterov E. N and Kobozev G. V. Surfactant of lungs, Kiev, 1981, bibliogr.; Laryushvina R. M. and P at x about fi-ska I am N. V. Biochemical diagnosis of a condition of surfaktantny system of lungs of a fruit and newborn, Pediatrics, No. 1, page 9, 1980; Magomedov M. K., T and - t about in and G. P. and B and r and N about in and M. V. Morfologiya of an atelectasis of lungs at the operated and not operated patients taking into account a condition of pulmonary surfactant, Arkh. patol., t. 41, No. 11, page 57, 1979; Romanova L. K., etc. The adaptable mechanisms providing surface intention in lungs, Fiziol. person, t. 3, No. 6, page 1006, 1977; About b 1 a d e n M. Factors influencing surfactant composition in the newborn infant, Europ. J. Pediat., v. 128, p. 129, 1978; Robertson B. Surfactant substitution, Lung, v. 158, p. 57, 1980; Scarpelli E. M. The surfactant system of the lung, Philadelphia, 1968, bibliogr.
A. A. Birkun.