Hormones synthesis, secretion and releasing.

Hormones classification (according to their chemical structure):

1) aminoacids derivates:

· thyroid hormones;

· adrenaline;

· hypophyseal hormones;

2) peptide hormones:

· hypothalamic neuropeptides;

· hypophysal hormones;

· pancreatic insular apparatus hormones;

· parathyroid hormones;

3) steroid hormones (are formed from cholesterine):

· suprarenal glands hormones;

· sexual hormones;

· renal hormone – calcitryol.

Hormones are usually deponated (accumulated) in those tissues where they are formed (thyroid follicles, suprarenal glands medulla - as granules). But some of them are deponated by non-secretory cells (cathecholamines are catched by blood cells).

Hormones transport is performed by internal environment fluids (blood, lymph, cells microenvironment) in 2 forms – bound and free. Bound (with erythrocytic, thrombocytic membranes and proteins) hormones have low activity. Free hormones are the most active, they pass through barriers and interact with cellular receptors. Hormones metabolic transformations lead to new informational molecules forming with qualities different from main hormone. Hormonal metabolism is performed by means of enzymes in endocrine tissues themselves and also in liver, kidney and tissues-effectors. Hormonal information molecules and their metabolites releasing from blood is realized through kidney, sweat glands, salivary glands, bile and alimentary juices.

Hormones action mechanism. They differentiate several kinds, types and mechanisms of hormones action to tissues-targets:

metabolic action – causes metabolism change in tissues (cellular membranes permeability, cellular enzymatic activity, enzymatic synthesis change);

morpho-genetic action – hormones influence on processes of structural elements shape-forming, differentiating and growth (genetic apparatus and metabolism change);

kinetic action – ability to switch on effector activity (oxytocine – uterus musculature contraction, adrenaline – glycogenolysis in lirer);

corrigating action – organ activity change (adrenaline – heart contractions frequency increasing);

reactogenic action – hormone ability to change tissue reactivity to the action of the same hormone, other hormones or mediators (glucocorticoids release adrenaline action, insuline increases somatotropine action realizing).

Hormones action ways to cells – targets – can be realized as 2 possibilities. Hormone action from cellular membrane surface after binding with specific membrane receptor and after that switching on biochemical reactions chain in membrane and cytoplasm. Peptide hormones realize their activity by this way. Another way – penetrating the membrane and connection with cytoplasmic receptors after which hormone-receptor complex penetrates nucleus and cellular organoids. Such way is a characteristics of steroid and thyroid hormones.

In peptide, protein hormones and catecholamines hormone-receptor complex leads to membrane enzymes activation and hormonal regulative effect secondary messengers formation. They know next secondary messengers systems:

· adenylatecyclase-cyclic adenosinemonophosphate (cAMP);

· guanylatecyclase-cyclic guanosinemonophosphate (cGMP);

· phospholipase C – inositoletryphosphate (IP3);

· ionized calcium.

In the most organism cells practically all messengers mentioned above with the exception of cGMP are present or may be formed. There are different interrelations between them (equal participation, one – main, others – agonists, act simultaneously, double one another, are antagonists). In steroid hormones membrane receptors provides specific hormone recognition and its transport to cell; special cytoplasmic protein – receptor with which hormone is connected – is located in cytoplasm. Then interaction of this complex with nuclear receptor occurs and reaction cycle with DNA participation and ending protein and enzymes biosynthesis on ribosomes is switched on. Additionally, steroids change intracellular cAMP and ionized calcium content. In this aspect different hormones action mechanisms have similar features.

In last tens years tissue hormones large group has been discovered, for example, alimentary tract, kidney and practically all the tissues hormones. Prostaglandins, kinins, histamine, serotonin, cytomedin s and others belong to them. Second half of last century in biology and medicine is characterized by fast development of peptide role study in organism activity. Every year great amount of publications dedicated to different physiologic functions course appear. Nowadays from different (practically all) organism tissues more than 100 peptides are extracted. One group of neuropeptides is among them. To present time peptide regulators are found out in alimentary tract, heart-vascular system, respiratory and excretory organs. Thus, there exists diffused neuroendocrine system called sometimes third nervous system. Endogenous peptide regulators containing in blood, lymph, interstitial liquid and different tissues, can have at least three origins of their development: endocrine cells, organ neuronal elements and peptide axonal transport depot from central nervous system. Brain synthesizes constantly and thus contains with the small exception all peptide bioregulators. That’s why brain is called to be endocrine organ. At the end of last century information molecules existance in organism cells was proved. These molecules provide interactions in nervous and immune system activity. They received the name cytomedines. These are substances realizing connection between small cellular groups that influence greatly on their specific activity. Cytomedines carry definite information from cell to cell. Such information is written by means of aminoacids sequences and conformational modifications. Maximal effect cytomedines cause in tissues of organ from which they are excreted. These substances support definite cell correlation in populations situated on different developmental stages. They perform informational exchange between genes and intercellular environment. They participate in cells differentiation and proliferation processes while changing genome functional activity and protein biosynthesis. Nowadays thesis about united neuro-endocrine-cytomedine regulatory system in organism is putted forward.