Effect of exogenous angiotensin II infusion after one year of captopril therapy in essential hypertension.

The effect of exogenous angiotensin II on plasma renin activity (PRA), plasma renin concentration (PRC) and plasma aldosterone (PA) was investigated in a group of 8 patients with essential hypertension after one year of captopril therapy. The results were compared with those obtained in a group of 18 normotensive volunteers not on captopril. Angiotensin II was infused at increasing doses until a pressor response (increase of diastolic blood pressure by 20 mm Hg) was evoked. The normotensive volunteers exhibited the expected decline of PRA during angiotensin II infusion. However, no significant change was observed in PRA nor in PRC levels in the group of hypertensive patients. The PA values increased significantly both in volunteers and patients (P less than 0.02). The dose of angiotensin II necessary to evoke a pressor response was higher in the hypertensive patients than in the normotensive volunteers (6.0 +/- 2.6 s.d. ng/kg/min vs 2.5 +/- 0.9; P less than 0.01). We conclude that patients with essential hypertension, after chronic treatment with captopril, show no inhibition of renin secretion in contrast with the controls. They also require more angiotensin II to evoke a pressor response during infusion of this peptide.