Proposed mechanisms of propranolol's antihypertensive effect in essential hypertension.

We studied the antihypertensive effect of propranolol alone and in combination with diuretics in 13 patients with high, 18 with normal and nine with low-renin essential hypertension whose blood-pressure response to diuretics was previously established. Propranolol (160 mg daily) significantly lowered mean arterial pressure in high-renin (129 +/- 2.6 to 114 +/- 2.1 mm Hg) and normal-renin (131 +/- 2.7 to 119 +/- 3.5 mm Hg) patients but not in low-renin patients. A positive correlation (r = 0.36, P less than 0.05) between fall in pressure and fall in plasma renin activity occurred at this dose when the whole group was considered. An antihypertensive effect occurred in both high-renin and low-renin hypertension during large-dose (320 to 960 mg daily) propranolol therapy. This effect was independent of changes in plasma renin activity. The antihypertensive effects of propranolol and diuretics were additive in normal-renin and high-renin hypertension. These data suggest that propranolol's pressure-lowering activity is due to both renin-dependent and renin-independent effects.