[Effect of alpha, beta blocker, labetol on the angiotensin renin system in arterial hypertension].

The effect of labetalol, a new alpha and beta adrenergic blocker, on blood pressure, heart rate, plasma renin activity (PRA), and urinary aldosterone excretion was assessed in 23 essential hypertensive patients, divided in 2 subgroups: 11 with normal electrocardiogram and 12 with left ventricular hypertrophy (LVH). In the first subgroup significant differences were found in the arithmethyc mean for sistolic blood pressure in sitting position (control: 166.1 +/- 17.2 mm of Hg treatment: 153.9 +/- 13.8, p less than or equal to 0.005) and in standing position (control: 165.3 +/- 17.3, treatment: 152.8 +/- 13.8, p less than or equal to 0.005) and for diastolic blood pressure (control: 102.7 +/- 12.6 to 89.9 +/- 10.1, p less than or equal to 0.001 and 103.2 +/- 11.8 to 91.2 +/- 10.8, p less than or equal to 0.001; in sitting and orthostatic positions, respectively.). No significant differences were found in the group with LVH. Heart rate decreased in the total population during treatment (- 6.0 +/- 7.5, p less than or equal to 0.05 and - 5.4 +/- 7.5 beats per minute, p less than or equal to 0.05 in sitting and orthostatic positions, respectively. PRA diminished in 12 of 15 cases studied (- 2.5 +/- 4.65 ng/ml/hr., p greater than 0.5). Correlation coefficient between decrements of diastolic blood pressure (sitting position) and ARP was 0.637. Aldosterone decreased in a non significant way during treatment. These data support the thesis of an important role of the adrenergic system in the pathogenesis of non complicated essential hypertension and, therefore, simultaneous alpha and beta receptor blockade in these cases has a better therapeutic effect. The good correlation between the decrements of ARP and blood pressure suggests an intervention of the inhibition of renin angiotensine system, brought about by the blocker property of labetalol, in the antihypertensive mechanism of the drug.