Contrasting effects of acute beta blockade with propranolol on plasma catecholamines and renin in essential hypertension: A possible basis for the delayed antihypertensive response

Blood pressure, heart rate, plasma renin activity, plasma norepinephrine and plasma epinephrine were determined in 11 patients with essential hypertension at rest before and 15, 30, 45, and 60 minutes after an intravenous infusion of 0.12 mg./Kg. propranolol given over five minutes. After propranolol mean blood pressure was unchanged; heart rate decreased by 14 per cent within 15 minutes and showed no further changes. Plasma renin activity decreased progressively by 48 per cent 60 minutes after propranolol, whereas plasma norepinephrine and epinephrine were always higher after propranolol than control values. Increases in norepinephrine was statistically significant at 30, 45, and 60 minutes (respectively 49, 39, and 45 per cent, P