renin-angiotensin system (redirected from Renin-angiotensin-aldosterone axis)

renin-angiotensin system,

the regulation of sodium balance, fluid volume, and blood pressure. In response to reduced perfusion, renin is secreted, which hydrolyzes a plasma globulin to release angiotensin I, which is rapidly hydrolyzed to angiotensin II, a powerful vasoconstrictor; angiotension II also stimulates aldosterone secretion, which causes sodium retention, an increase in blood pressure, and restoration of renal perfusion, which shuts off the signal for renin release (negative feedback). Angiotensin-converting enzyme also deactivates bradykinin, a vasodilator. Also called renin-angiotensin-aldosterone system.

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renin

a proteolytic enzyme synthesized, stored and secreted by the juxtaglomerular cells of the kidney; it plays a role in regulation of blood pressure by catalyzing the conversion of the plasma glycoprotein angiotensinogen to angiotensin I. This, in turn, is converted to angiotensin II by an enzyme that is present in relatively high concentrations in the lung. Angiotensin II is one of the most potent vasoconstrictors known, and also is a powerful stimulus of aldosterone secretion.

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renin-angiotensin system

renin, secreted by the juxtaglomerular apparatus, activates the precursor angiotensinogen. This liberates angiotensin I, then angiotensin II, a vasoconstrictor and stimulant to the secretion of aldosterone.

big renin

a relatively inactive protein with a higher molecular weight than normal renin, which is activated after exposure to low pH or to proteolytic enzymes.