Renin is a hormone-like enzyme (endopeptidase) whose task is to split off angiotensin I from angiotensinogen in the metabolism. The determination of the renin value serves to assess the renin-angiotensin system. Renin is produced in the cells of the juxta-aglomerular apparatus of the kidneys. Extrarenal it is formed in the uterus, liver and vascular walls, among others.
Renin
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Renin secretion is controlled by various stimuli: reduced blood flow to the kidneys (e.g. acute decrease in blood pressure or circulating plasma volume or as a result of renal artery stenosis. Furthermore, by the composition of the fluid in the distal renal tubule (especially by reduction of the NaCl concentration) as well as via innervation by sympathetic nerves of the kidney (beta-1-receptors).
Renin release is inhibited mainly by angiotensin II and aldosterone released via angiotensin II. An increase in the extracellular K concentration leads via increased aldosterone secretion to feedback inhibition on renin production to a lowered renin concentration in the blood.
The non-peptide selective renin inhibitor aliskiren lowers blood pressure by lowering plasma renin concentration and thus has an antihypertensive effect.