Plasma renin activity in phaeochromocytoma: effects of beta-blockade and converting enzyme inhibition

We measured plasma renin activity and plasma catecholamines in 26 untreated patients with phaeochromocytoma, 18 untreated patients with primary hypertension, and 10 normal control volunteers. Plasma renin activity measured in patients in the supine position, standing position and after walking for 1 h was higher in the subjects with phaeochromocytoma than in those with primary hypertension or in the volunteers (F = 9, P less than 0.001). In all three situations, renin activity was closely correlated with noradrenaline levels in the phaeochromocytoma patients (r = 0.545, r = 0.600, and r = 0.739; P less than 0.01) but not in the subjects with primary hypertension or in the volunteers. The cardioselective beta-blocker acebutolol reduced heart rate, mean blood pressure and renin activity by averages of 20, 12 and 89% respectively in the seven phaeochromocytoma patients given the drug. Captopril decreased mean blood pressure by 19% and raised renin activity by 293% in the nine phaeochromocytoma patients tested. These findings show that in phaeochromocytoma, hypertension is accompanied by high renin levels and that renin release is stimulated in response to noradrenaline overflow. The hypotension observed in response to beta-blockade and captopril provides indirect support for the possibility that renin-dependent mechanisms are involved in the hypertension of phaeochromocytoma.