Biochemistry

13.3 ROLE OF HORMONES IN THE REGULATION OF SUBSTANCE EXCHANGE Humoral regulation is carried out by transfer of biologically active substances of hormones in liquid media. Hormones (from Greek. Hormao - set in motion, induce) are biologically active substances of an organic nature. They are produced by specialized cells of the endocrine glands and, acting with body fluids, affect the metabolism and physiological functions of the corresponding organs - “ targets ” . Endocrine glands are hypothalamus, pituitary, thyroid, parathyroids , thymus gland, adrenal glands and pancreas and sex glands. Hormones belong to the group of informons, they can be formed both in the endocrine glands (time hormones) and in the tissues of other organs (histone hormones). The biological significance of hormones lies in their regulatory effect on a variety of processes in the body. They support homeostasis (constancy of the internal environment), participate in the adaptive activity of the body to changing conditions of the external and internal environment, affect the speed of chemical reactions, physiological functions, differentiation of cells, the mechanism of immunity, and mental activity. Hormones produced by the endocrine glands exhibit a high specificity of action. It manifests itself distantly, i.e., at a distance from the site of the hormone formation. In the cells of tissues that perceive hormones, there are specific proteins that have a special structure that allows them to interact with a specific hormone. The initial link in the action of hormones on the cell is the connection of the hormone with proteins - cell receptors. Hormones bind with receptors either on the outer surface of the plasma membrane or in the cytoplasm. However, in both cases, receptor proteins, due to their specificity, “ draw ” hormones into the cell and then transmit their signals to enzymes. Hormones action is aimed mainly at regulation of metabolic processes in cells by changing the rate of enzymatic conversion of substances. A number of hormones affect the synthesis of enzymes. Such an action is exerted by hormones of the cortical substance of the adrenal glands (glucocorticoids), thyroid hormones (thyroxine), pituitary gland (growth hormone) - somatotropic hormone. These hormones are characterized by the ability to penetrate into the cell and connect there with specific receptors in the cytoplasm. In this case, a hormone-receptor complex is formed, which, after molecular restructuring, leading to its activation, is able to penetrate into the cell nucleus. In the nucleus, the hormone-receptor complex interacts with chromatin, 282