HORMONAL REGULATION

From Big Medical Encyclopedia

HORMONAL REGULATION — set of the regulating impact of various hormones on functions of an organism. Having arisen at a certain stage of evolutionary development, is earlier form, than nervous control, and plays a role of a coupling link between c. N of page and fabrics. Plays an important role in maintenance homeostasis (see) and in adaptation of an organism to the changing conditions of surrounding and internal environment (see. Adaptation ). It is carried out by change of secretion of hormones in response to external or internal actions and can be implemented by the next way: ts.n. page —> a hypothalamus (rilizingfaktor) —> a hypophysis (triple hormones) —> peripheral closed glands (hormones) —> bodies and fabrics (see. Gipotalamo-gipofizarnaya system ).

History of development of representations about is history of development of endocrinology and biology in general; the problem Is closely connected with achievements in the field of a research of hormones (see. Hormones ) and with questions of nervous control (see. Neurohumoral regulation ). Examination physical. - chemical and molecular bases it is connected with studying of biosynthesis of protein, with researches of structure and function biol, membranes, enzymes and with other achievements of biochemistry.

As in general is result of influence of various hormones, separate fiziol, the effect is defined by effect of this or that hormone. Influences all levels of the organization of live system. Depending on specificity of hormonal action it can be or rather specialized as, e.g., selective regulation of aldosteronomas of transport of sodium and potassium through epithelial structures of kidneys, or wide as regulation of oxidizing processes, processes of a differentiation, growth, development etc. However anyway a specific object — chemical reactions of a live organism, and this its aspect has the greatest theoretical and practical interest.

Among mechanisms influence of hormones on biosynthesis Is most studied proteins (see). Influence of hormones on the speed of biosynthesis of protein is the cornerstone of regulation of such processes as growth, development, a differentiation of fabrics, synthesis of fabric proteins, maturing of follicles of an ovum etc.

is most brightly expressed by influence of hormones on synthesis of enzymes since all chemical reactions in an organism are catalyzed enzymes (see). It is most studied synthesis of two enzymes of amino-acid exchange: tryptophane (tryptophane oxygenase or triptofanpirrolaza) and tyrosine (tyrosine-aminotransferase). It is established that glucocorticoids at animals and the person considerably increase the speed of synthesis of these enzymes. Similar data are obtained also concerning influence of other hormones on enzymes, and quite often between hormones there is antagonistic relationship. It is possible to give data on opposite action of glucocorticoids and insulin on disintegration of glucose in fabrics as an example: glucocorticoids brake it, and insulin — raises. This fact is explained by opposite influence of the specified hormones on the enzymes catalyzing disintegration of glucose (a glucokinase, a fosfofruktokinaza, a pyruvatekinase) which quantity increases after administration of insulin and decreases after introduction of glucocorticoids. As for enzymes of synthesis of glucose (pyruvatecarboxymanholes, fosfoyenolpiruvatkarboksilaza, fruktozo-1, 6 diphosphatases and glyukozo-6-phosphatases), insulin suppresses their synthesis, and glucocorticoids raise. Influence of hormones on the speed of synthesis of protein is shown also to in vitro: thyroxine in concentration 6,6×10 - 5 The m stimulated full synthesis (5 chains of hemoglobin in reticulocytes of a rabbit. At clarification of a stage of biosynthesis of protein, on Krom it is carried out, it is established that it can be both a stage of a transcription, and a stage of broadcasting. Data on a possibility of influence of hormones on the speed of synthesis of information (matrix) RNA are obtained.

As the amount of active enzymes in fabrics is defined not only by the speed of synthesis, but also speed of their disintegration, exchange of fermental proteins can be an object. It is established that hormones can influence half-life of enzymes. E.g., after introduction by an animal of Prednisolonum half-life of alaninaminotranspherase in a liver decreases from 3,5 to 1,2 days, and after an incubation of tissue of liver with cortisol half-life of tyrosinetransaminase decreases from 11,1 to 3,7 o'clock.

Change of conformation (spatial structure) of enzymes can be one of ways that is illustrated by effect of estrogen and thyroxine concerning a glutamatdegidrogenaza. This enzyme in the presence of the specified hormones dissociates on subunits, and glutamatdegidrogenazny activity at the same time sharply decreases. Influence of hormones on conformation of fermental proteins is of great importance also because conformation defines stability of enzymes to various influences, and preservation of active conformation defines enzymatic activity. Data on increase in specific activity of enzymes under the influence of hormones without change of amount of enzymes are obtained. It is possible what in such cases consists in maintenance of conformation of enzyme, optimum for a catalysis. It is also necessary to consider what in a complete organism is carried out in interaction with other control mechanisms regulating the speed of enzymatic reactions.

The great value in implementation is attached cyclic 3', 5 '-AMF as to the intermediary in operation of many hormones. This connection is formed in an organism of ATP at means of enzyme of adenylatecyclase; disintegration 3', 5 '-AMF is catalyzed by phosphodiesterase. Through 3', 5 '-AMF is implemented influence of AKTG and luteinizing hormone on a steroidogenesis (see. Steroids ), and catecholamines, a glucagon and insulin — on a lipolysis (see. Lipometabolism ) and a glycogenolysis (see. Glycolysis ), hypothalamic rilizingfaktor — on release of tropny hormones of a hypophysis etc. Intracellular action 3', 5 '-AMF consists in its influence on activity of enzymes. Tsiklo-AMF connects inactive unit (receptor) of a protein kinase therefore the catalytic subunit is released and the activated protein kinase is formed. Tsiklo-AMF is not only the intermediary in implementation of effect of hormones, but participates as well in their secretion; it is shown, in particular, in the relation Aldosteronum (see) and calcitonin (see).

Very important party is influence of hormones on permeability of cellular membranes. These membranes to a large extent define physical. - a chemical condition of internal environment of a cell since through them there is transport of ions, waters, carbohydrates, amino acids, fats and other components of internal environment. A cellular membrane (see. Membranes biological ) has thickness apprx. 8 nanometers and consists of a dimolecular layer of the lipids covered on both sides with proteinaceous films. The membrane is not homogeneous throughout a cell and consists of various functional units. Insulin causes transition of a laminar form of a membrane in micellar (globular) that is followed by reorientation of polar groups of the Lipidic component and change of permeability owing to emergence of «channels». Influence of hormones on a functional condition of cellular membranes is very important link for three main reasons: 1) owing to an opportunity in such way to control permeability; 2) owing to a possibility of influence of hormones on activity of adenylatecyclase, edge in many fabrics «is built in» a membrane; 3) because metochny membranes are the first place of contact of the hormones arriving with blood with target organs.

Adenylatecyclase — complex enzyme of the lipoproteidny nature, and change of its spatial structure leads as to increase (or to decrease) quantities 5', 5 '-AMF, and to change of conformation of this site of a membrane.

Influence of hormones on membranes can be considered as one of links of initial interaction of hormones with fabrics, i.e. specific reception of hormones. The issue of penetration of proteinaceous hormones in a cell is not resolved finally yet, and believe that on a membrane there is a «starting» reaction untying the sequence of effects of these hormones. Concerning steroid hormones it is established that they get into cells and initially contact special receptor proteins. Most in detail this question is investigated for estrogen (see). In estrogenchuvstvitelny fabrics special proteins, «specifically connecting estrogen are found; at first hormone contacts receptors of cytoplasm, then is transferred to a kernel and there contacts other receptor protein then influences the genetic device of a cell. Possibly, binding takes place and for others steroid hormones (see), while for peptide hormones (see. Proteinaceous and peptide hormones ) and catecholamines activation of adenylatecyclase and the subsequent education 3', 5 '-AMF can be primary.

Has specific, sexual and age features which cornerstone distinctions or change of size and quality of secretion of separate closed glands, and also distinctions in sensitivity of fabrics to hormones are. Concerning specific differences it is possible to give an example of corticosteroid induction of tyrosineaminotransferase in a liver: at amphibians and fishes activity of enzyme almost does not change after introduction of cortisol, and at mammals and birds this activity sharply increases. In the embryonal period hormonal induction of enzymes is absent and appears for the first time during the period from several hours to several days after the birth. With age hormonal induction for one enzymes does not change, and for others or weakens, or even increases. It is possible that it is the cornerstone characteristic for during the aging of a diskoordination of regulation, i.e. at the heart of disturbance and dissociation of harmonious relationship of various types of regulation (see. Old age, aging ). Disturbance happens also at various patol, conditions of both an endocrine, and not endocrine etiology. Practically all endocrine diseases lead to frustration which expressiveness can be various. So, at the virilizing tumors of adrenal glands it is perverted characteristic of a female body owing to excessive receipt of androgens in an organism; at feminizing tumors there is a similar frustration characteristic of a male body owing to excess of estrogen. However and at not endocrine diseases, as a rule, there occur the changes though which not always are sharply expressed since endocrine system extraordinary of a labiln to any influences. It is quite often very difficult to draw line between homeostatic and patol, shifts. A peculiar character has change at tumors (e.g., in fabric of an experimental gepatoma at animals ability of some enzymes to change the activity in response to introduction of corticosteroids while in tissue of the liver adjoining on a tumor, this ability remains is lost). It is necessary to remember a possibility of serious violations also at purpose of hormonal therapy (see. Hormonal therapy ), especially at the long administration of hormones which is quite often leading to the expressed frustration of a metabolism.


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T. H. Protasova.

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