Inhibition of angiotensin converting enzyme by ramipril in serum and tissue of man

Studies in animal models have indicated that ramipril is a potent inhibitor of angiotensin converting enzyme (ACE) in serum and tissue. In our study, the normal range of ACE activity and the inhibitory effect of short-term oral administration of ramipril on ACE activity in human serum and tissue samples of renal cortex, heart and blood vessels were determined. ACE activity in the renal cortex (125.2 ± 11.5 nmol/mg per min) was >600 times that of the heart (0.20 ±0.01 nmol/mg per min), >500 times that of the veins (0.23 ±0.09 nmol/mg per min) and >150 times that of the arteries (0.80 ± 0.23 nmol/mg per min). ACE activity in the renal cortex and arteries 2h after last dosing was almost completely inhibited by ramipril whereas ACE activity in the veins and heart was inhibited to a lesser extent. Our results demonstrate in man, for the first time, an inhibition of tissue ACE following short-term oral treatment with an ACE inhibitor.