It allows to describe

It allows to describe easily phenomenology of action of hormones of one class through receptors of other class (for example, glucocorticoid action of a hydrocortisone through receptors or insulinic action of insulin through receptors), and there are circumstances at which such effects can matter. MOLECULAR MECHANISMS OF ACTION OF HORMONES For the last two decades the huge number of data on mechanisms of action buy order cipro of hormones [4] has been received, though many important details (for example how steroidno-retseptoraye complexes influence on activity of a chromatin by what the nature of "the second mediator insulin actions) are not found out yet. These mechanisms are more convenient for analyzing, having united to hormones in following groups: 1 - polypeptide hormones, catecholamins and rilizing-factors; 2 - steroid hormones, including vitamin D, and 3 - thyroid hormones (see chapter 4). Polypeptide hormones, catecholamins and rilizing-factors contact the receptors localised on a surface of cells. In the big number of cases linkage of hormones with their receptors leads to adenylatecyclase activation. It is fair for b-adrenergic agonists, a glucagon, , hormones groups (, , , ), some rilizing-hormones (LG-RG, ), , a calcitonin (possibly), , a vasopressin (), the factor of growth of nerves (). Owing to adenylatecyclase activation there is an accumulation .
As already it became perceptible, activates specific protein kinases (named tsamf-dependent protein kinases), various fibers in specific places. The fibers changed as a result , also mediate then hormonal effects. In many cases the reaction very short steps between interaction of a hormone with receptors of a cellular surface and the biological answer of a cell are unknown. Apparently, does not accept participation in these hormonal effects. The main candidates for a role of mediating factors in these cases are stimulation a complex of other kinds of enzymatic activity (other kinds , , AdF-ribozilirujushchej activity, etc.) Or ionic (for example, calcium) streams. To the hormones operating thus, other factors of growth, such, as erythropoetin, the factor of growth of fibroblasts (), the factor of growth of a false skin (), group of hormones (, chorionic and Prolactinum), a-adrenergicheskie the agonists, some rilizing-hormones, such, as , and also Oxytocinum and angiotensin concern insulin, and factors close to them, such, as the activity stimulating reproduction of cells () and not suppressed insulinoid activity (). Mentions and two other lines of receptors of polypeptide hormones and catecholamins deserve. First, the homologous hormone usually reduces (negatively regulates) sensitivity of cells to it. As a rule, it is caused basically by a caused hormone reduction of number of own receptors. However the hormone can reduce also cellular sensitivity to itself, influencing on the components of reaction localised more buy acomplia aventis rimonabant sanofi distally of a receptor. Such negative regulation represents the mechanism type which is imposed on other mechanisms of integration. Probably, it can serve and protect an organism from excessive influence of hormones at their high maintenance in case of sharp and long stimulation of their production. However this general rule has also exceptions, and in some cases hormones can raise cellular sensitivity to the action (for example, angiotensin and adrenals, Prolactinum and a mammary gland). Secondly, superficial complexes can be exposed to "internalization" in blisters in a cell. Concerning this mechanism appears cholesterol of the biosynthesis essential to inhibition. After blisters with the intracellular lysosomes containing enzymes, cholesterol can be split off from and in a free kind to operate in a cell with the help yet not taped receptors. Concerning polypeptide hormones and catecholamins the role of "internalization" of a hormone is unknown. Available data testify that in some cases "internalization" is not an obligatory condition of hormonal effect (for example, for the hormones activating adenylatecyclase); the question is activly investigated, whether she plays roles in hormone delivery to intracellular scenes of action in other cases. However "internalization" can take part in processes of degradation of a hormone and-or a receptor. Steroid hormones, at least in most cases, operate, obviously, intracellularly. They get into a cell by means of unknown mechanisms, but, probably, by passive diffusion and contact intracellular receptors which on the localisation can be both cytoplasmatic, and nuclear. Interaction of a hormone with a receptor causes the conformation changes of the last allowing it to contact by a nuclear chromatin. Having contacted a chromatin, the complex can enlarge (or to reduce) formation specific .