Possible Role of Renin in Hypertension as Suggested by Renin-Sodium Profiling and Inhibition of Converting Enzyme

To block renin activity, a nonapeptide converting-enzyme inhibitor was given to 65 seated hypertensive patients. Depressor responses occurred only when control plasma renin activity exceeded 2 ng of angiotensin I per milliliter per hour and correlated directly in amplitude with control plasma renin activity and with induced increments in activity (P less than 0.001 for both). Depressor responses, like renin activity, were characteristic for renin subgroups as defined by renin-sodium profiling. Before and after sodium deprivation, the nonapeptide reduced diastolic pressure in all patients with high renin (by 17.3 and 19.8 per cent) and most patients with normal renin (by 9.1 and 17.7 per cent). Low-renin patients remained unresponsive. This enzyme blockade may cause bradykinin accumulation. But if, as seems likely, depressor responses are due to blockade of angiotensin II formation, the results indicate that, irrespective of sodium balance, measurements of plasma renin activity reflect its contribution to blood-pressure maintenance. The results suggest broad participation of the renin system in common forms of hypertension.