THE EFFECT OF PROPRANOLOL ON PLASMA RENIN ACTIVITY AND BLOOD PRESSURE IN MILD ESSENTIAL HYPERTENSION

Abstract

Abstract. Fourteen male patients with mild to moderate essential hypertension have been studied with regard to plasma renin activity (PRA) after acute and prolonged β‐adrenergic blockade with propranolol. Initial PRA was determined after four weeks of placebo treatment. Before propranolol was given PRA rose in response to 10 min of 45° head‐up tilt from 151.7 ng/100 ml/h to 248.7 ng/100 ml/h (p<0.01). After acute administration of propranolol 0.22 mg/kg b.wt. i.v. and following repeated tilt for 10 min PRA only rose to 204.7 ng/100 ml/h (n.s.). Following four weeks of oral propranolol treatment at 160–320 mg daily PRA after tilt was 39.0 ng/100 ml/h. Thus a significant reduction of PRA had taken place (p< 0.005) to a level constituting only 15% of the initial PRA after tilt.The reduction of blood pressure (BP) after four weeks of propranolol treatment was also significant. Diastolic BP was reduced by 19 mmHg(p< 0.001). The changes in BP and tilted PRA were not significantly correlated (r=0.449, p<0.10). These results indicate that propranolol causes a marked reduction of PRA in addition to its hypotensive effect. However, this does not necessarily imply that there is a direct causal relationship between the effect of propranolol on PRA and its effect on BP.