Atrial natriuretic peptide and the natriuresis due to acute beta-blockade in conscious hypertensive rats

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 atenolol 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 less than .001) significantly. The atenolol therapy decreased heart rate (P less than .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 beta-adrenoreceptor blockers, by a reduction in PRA and PA levels and a vasodilatative effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of arotinolol on hemodynamics and plasma atrial natriuretic peptide at rest and during stress in spontaneously hypertensive rats

We investigated the effects of chronic treatment with arotinolol, a beta-blocker with weak alpha-blocking potency, on hemodynamics and plasma levels of catecholamines and atrial natriuretic peptide (ANP) at rest and during stress in spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. At rest, arotinolol treatment decreased mean arterial pressure (MAP), cardiac index (CI) and heart rate (HR), with no changes in total peripheral resistance index or regional hemodynamics in SHR. Acute stress caused more remarkable hemodynamic changes in SHR. During stress, arotinolol decreased MAP, CI and HR, and reduced myocardial and skeletal muscle flow and splanchnic, renal, cerebral and cutaneous vascular resistance in SHR. Arotinolol's effects were much less in WKY. Stress also increased the plasma catecholamine and ANP levels in SHR. Arotinolol raised these hormones in both strains at rest and in SHR during stress. Thus, arotinolol treatment exerted greater suppressive effects on the resting and stressed hemodynamics in SHR, with associated increases in the plasma catecholamine and ANP levels.