plasma renin activity, the action of the enzyme renin (produced by the kidney), measured in plasma to aid in the diagnosis of adrenal disease associated with hypertension. The normal adult value in plasma is 0.2 to 4 ng/mL/hr, depending on salt intake and the time the patient is in an upright position before a renin activity test. An upright position raises production of renin, and a high salt intake lowers it.
