1. The plasma aldosterone responses to exogenous angiotensin II and adrenocorticotropic hormone (ACTH) were studied before and after 1 month of propranolol therapy (120–240 mg/day) in eight patients with essential hypertension.
2. Basal supine plasma renin activity was decreased (P < 0.001) after propranolol, whereas plasma aldosterone was unchanged. After 3 h of upright posture the increases in both plasma renin activity and aldosterone were decreased (P < 0.05) after propranolol.
3. Plasma aldosterone responses to exogenous angiotensin II and ACTH were not significantly different after propranolol. Serum and urinary electrolytes and plasma cortisol were also unaffected by propranolol therapy.
4. It is concluded that changes in adrenal sensitivity are not responsible for maintaining unchanged supine plasma aldosterone concentrations after β-adrenoceptor antagonism in essential hypertension.