Inhibition of the Renin Angiotensin System in the Treatment of Hypertension
Renin is a proteolytic enzyme that is synthetized, stored and secreted mainly by the juxtaglomerular apparatus of the kidney. The release of renin is regulated a.o. by renal baroreceptors, by sodium-sensitive mechanisms at the level of the macula densa, by the sympathetic nervous system, prostaglandins and angiotensin II. Renin acts on its substrate, angiotensinogen, an alpha-2-globulin produced in the liver and present in the plasma to form the decapeptide angiotensin I, which is practically devoid of pressor activity. The converting-enzyme, a peptidyl-dipeptidase, converts angiotensin I to angiotensin II by splitting off the dipeptide histidyl-leucine at the C-terminal of the decapeptide. The pulmonary circulation is the main site of conversion, but converting-enzyme is also present in the plasma, in the splanchnic system, in the kidney and in several other tissues. Angiotensin II is the effector hormone of the system in man. Its most important actions are direct pressor effects on the arteriolar smooth muscle, stimulation of the aldosterone secretion by the adrenal gland, and effects on the central and peripheral nervous system; these actions result in an increase of blood pressure and in salt and water retention.
KeywordsAngiotensin Converting Enzyme Renin Angiotensin System Juxtaglomerular Apparatus Sodium Depletion Plasma Renin Level
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