INCRETION - allocation by specialized cells of biologically active agents (hormones) directly through a cell wall without disturbance of its anatomic integrity in intercellular substance, and from there in blood.
The concept «incretion» was entered in 1855 by K. Bernard who suggested to allocate special group hemadens (see) — the secretory anatomic educations which do not have a special output channel for the substances synthesized by them (glands having an output channel carry to group of glands of external secretion).
Century of page is essential for life activity of a human body and animals. Release of the gormonalnoaktivny substances which are formed, as a rule, in small amounts directly in blood provides bystry receipt them to target organs. In the course of evolution V.'s emergence of page reflected the need for remote regulation of functional systems of the higher organisms. From the molekulyarnobiologichesky point of view, development of hormonal regulation represented replacement of the mechanism of substrate induction of biosynthesis of proteins (at the lowest organisms) on induction by special warning agents — hormones (see).
Biochemical, the mechanisms which are the cornerstone of V. of page, in different closed glands depending on chemical structure of the emitted hormones and the nature of their biosynthesis are various. In glands (adrenal glands, gonads) cosecreting steroid hormones, the corresponding steroids, as a rule, do not collect, and are allocated in blood in process of their education. At the same time synthesizable steroids are taken lipidic elements of cytoplasm of a steroidsekretiruyushchy cell and transported in extracellular space. Proteinaceous and peptide hormones can collect in glands forming them. So, iodinated hormones of a thyroid gland come to blood in process of euzymatic splitting of thyreoglobulin colloid; the insulin cosecreted by islands of a pancreas comes to blood after splitting of pro-insulin.
Regulation of processes of V. of page has in general neurohumoral character (see. Neurohumoral regulation ). Direct regulatory impact on activity of a number of peripheral glands B. of page is exerted tropny hormones of a hypophysis (see) which, apparently, stimulate biosynthesis cyclic 3,5 adenosinemonophosphates, activating then synthesis of hormones in the corresponding gland.
Release of tropny hormones of a hypophysis is controlled by a hypothalamus by secretion directly in portal system of vessels of a hypophysis of special low-molecular peptide substances. These substances either stimulate (rileasing-factors), or slow down (the inhibiting factors) secretion of hypophyseal hormones. Activity of a hypothalamus is under control, on the one hand, of nervous impulses, and with another — hormones of peripheral glands.
Some peripheral glands B. of page along with regulation like hypothalamus — a hypophysis — peripheral gland are controlled as well by those metabolites, education or utilization of which are regulated by the cosecreted hormone. It first of all belongs to hormone of incretory tissue of pancreas — to insulin (dependence on the level of glucose in blood), and also to parathormone of epithelial body and a calcitonin of a thyroid gland (their dependence on the level of calcium). Production of hormones of a medulla of adrenal glands is regulated by directly sympathetic nervous system.
The main method of a research B. of page is determination of level of hormones and their metabolites in peripheral blood and urine. In rare instances definition is carried out to blood, flowing from gland. Use of highly sensitive methods (with use, e.g., of radioisotopes) gives the chance to determine the average speed of secretion of a number of hormones within a day. However in the analysis of the obtained data it is necessary to consider that in many glands V.'s process by the village is changeable. It is carried out by very short-term (pulse) emissions which are often repeating for days; in intervals between impulses hormone can not be found.
Disturbance of process of V. of page can be as acquired (an inflammation, sclerous process, tumoral growth), and hereditary character (disturbance of education in iron of any enzyme). The change of a metabolism caused by deficit of any hormone korrigirutsya by introduction to an organism of this hormone (see. Hormonal therapy ) or the drugs stimulating process of formation of hormone in iron.
Supersecretion of hormones is suppressed introduction of blockers and partial or full removal of gland.
See also Secretion .
Bibliography Grollman A. Clinical endocrinology and its physiological bases, the lane with English, M., 1969; Modern questions of endocrinology, under the editorship of N. A. Yudasva, century 3 — 4, M., 1969 — 1972; E with to and I. A N. Fundamentals of physiology of closed glands, M., 1968; In e of of n and of d C1. Sur le mecanisme de la formation du sucre dans le foie, C. R. Acad. Sci. (Paris), t. 41, p. 461, 1855; L a b h a r t A. Klinik der inneren Sekretion, u.a., 1971.
B. V. Pokrovsky.