Short-Term Effects of Atenolol and Nifedipine on Atrial Natriuretic Peptide, Plasma Renin Activity, and Plasma Aldosterone in Patients with Essential Hypertension

The short-term effects of atenonol and nifedipine on plasma levels of atrial natriuretic peptide (ANP), plasma renin activity (PRA), and plasma aldosterone (PA) were studied in two groups of patients with uncomplicated essential hypertension. Urinary catecholamines, and sodium and potassium excretion were also studied. A group of 20 patients with hypertension, after a wash-out period of at least 10 days, was randomly subdivided into two protocol therapy subgroups. One group (six men and four women) received atenolol (100 mg/d), and the other group (six men and four women) received nifedipine (30 mg/d). Circulating plasma levels of ANP, PRA, and PA were determined by radioimmunoassay, and other variables were determined by routine laboratory techniques before therapy and at day 3 and day 7 after the treatment began. Arterial blood pressure and heart rate were monitored during the study. Both drugs reduced arterial blood pressure (P < .001) significantly. The atenonol therapy decreased heart rate (P < .001), increased plasma ANP levels and urinary catecholamine excretion, and decreased PRA and circulating PA levels. Nifedipine treatment did not modify plasma ANP values, whereas it increased PRA and PA circulating levels and urinary catecholamine excretion. No differences were shown for urinary volume, urinary sodium, and potassium excretions during the two different treatments. These findings suggest that the increased plasma ANP levels could contribute to the antihypertensive effects of the β-adrenoreceptor blockers, by a reduction in PRA and PA levels and a vasodilatative effect. On the other hand, short-term treatment with nifedipine increased PRA and PA circulating levels without modifying ANP values, which suggests that its hypotensive effects are not mediated by ANP.