Plasma active and inactive renin in man during infusion of angiotensin II with and without prior administration of nifedipine.

Release of active renin is inhibited by angiotensin II. To determine whether plasma inactive renin is also sensitive to this hormone, the effect of stepwise infusion of angiotensin II at 5,10 and 20 ng/kg/min on active and inactive renin levels was measured in six salt-replete normal subjects. Each subject received two infusions of angiotensin II on each of 2 study days. The calcium antagonist drug nifedipine (20 mg) or placebo was administered between the angiotensin infusions on each study day. During control infusions there was a significant decline in plasma active renin but no change in inactive renin was observed. Active renin concentration was increased after nifedipine treatment and suppressed to a similar degree by angiotensin II as in control infusions, with no corresponding changes in inactive renin. These studies suggest that plasma inactive renin levels are not subject to feedback inhibition by angiotensin II, and that inactive renin is not a physiologically important precursor of active renin in man.