The renin-angiotensin system

The renin-angiotensin system - the group of biologically active substances, which interaction leads to the formation of pressure factors that play a role in the regulation of vascular tone.
The first link of the renin-angiotensin system is produced by the kidneys enzyme renin, not having the Pressor activity. Renin is secreted juxtamedullary apparatus of kidneys (see). The granular level of cells of this apparatus clearly varies with changes in blood pressure and violations of water-salt metabolism, playing important role in the regulation of vascular tone. A small number of renin allocated memory in the blood of healthy people and animals. The sharp increase in the number allocated in the blood renin in violation of renal blood flow (reducing blood flow, reducing vnutripuzarnogo pulse pressure). If you re a frequent introductions of renin a state of insensibility to him (tahifilaksiya).
Angiotensinogen (renin substrate, activator renin), part A2-globulin fraction of plasma, formed in the liver under the influence of the renin breaks up Decapeptide - angiotensin I, not having the Pressor activity. Under the influence of the so-called converting enzyme angiotensin I to disintegrate inactive dipeptide and angiotensin II with high Pressor activity. The chemical nature converting enzyme is unknown; it hydrolyzes the relationship between histidine and phenylalanine.
Angiotensin II is the final link of the renin-angiotensin system - is a oktapeptid, which consists of 8 amino acids. Synthesized numerous analogues of angiotensin II, part of which is not inferior to him on his biological activity. Angiotensin II is destroyed in the blood of the enzyme angiotensinase contained in extracts of many tissues (liver, kidney, spleen and other).
The role of the renin-angiotensin system in the pathogenesis of hypertension has been the subject of comprehensive research. A widespread view, the Goldblatt and other authors on the decisive role of the renin-angiotensin system in the pathogenesis of hypertension currently exposed to serious and valid criticism.
According to this view increased blood pressure in hypertension due to increased excretion by the kidneys renin in violation of renal blood flow and education as a result of this chain reactions increased number of angiotensin II with high Pressor activity. Consequently, essential hypertension of the content of renin and angiotensin in the blood should be increased, and the removal of the kidney with impaired circulation must be accompanied by a reduction in blood pressure.
However, the increase in the content of renin and angiotensin in blood, normalization of arterial pressure when removing the ischemic kidney observed only in the acute stage of experimental renal hypertension. In the chronic stage renal hypertension and the majority of hypertensive patients with the content of renin in the blood is not increased, and the removal of the kidneys of animals with chronic renal hypertension is not accompanied by normalization of blood pressure. Therefore, the renin-angiotensin system can play a decisive role only at the early stage of development experimental renal hypertension and hypertensive disease in humans, and later in pathogenetic chain is included new vnepochechny link (see Hypertension, pathophysiological mechanisms).