Medical Health Encyclopedia

Renin

Patients with essential hypertension may have renin and aldosterone levels checked to evaluate if they are salt-sensitive, which causes a low renin with normal aldosterone levels, and this helps to guide the physician in choosing the correct medication for these patients. Salt-sensitive patients with low renin hypertension respond well to diuretic medications.

Renin is an enzyme released by specialized cells of the kidney into the blood. It is in response to sodium depletion or low blood volume. Renin converts angiotensinogen (a protein released into the blood by the liver) to angiotensin I.

Angiotensin I is converted to angiotensin II by an enzyme in the veins of the lungs. Angiotensin II acts on the adrenal cortex to stimulate the release of aldosterone. Aldosterone acts on the distal tubules of the kidneys to decrease the loss of sodium ions and secondarily fluid. This has the effect of increasing blood pressure. In addition, angiotensin causes constriction of small blood vessels, which also increases blood pressure.

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