Renin Angiotensin Aldosterone Axis

Renin angiotensin aldosterone axis

Decreased blood flow to the kidneys cause them to secrete renin. Renin increases the production of angiotensin, a potent vasoconstrictor which causes contraction of smooth muscles of the blood vessels. Specifically it is angiotensin II which is one of the most potent vasoconstrictors. Renin converts angiotensinogen to angiotensin I, which is converted to angiotensin II by angiotensin converting enzyme (ACE). ACE is present mostly in the lungs.

Angiotensin II stimulates the secretion of aldosterone, a hormone which causes salt and water retention. Aldosterone is secreted from the adrenal cortex. Renin is a proteolytic enzyme secreted by the juxta glomerular apparatus of the kidney. Angiotensinogen is synthesised in the liver.