Acute effect of an alpha1-adrenoceptor antagonist on urinary sodium excretion,plasma atrial natriuretic peptide,arginine vasopressin,and the renin-aldosterone system in healthy subjects

Summary To elucidate the mechanism underlying the sodium retention caused by₁-adrenoceptor blockade in man, a placebo-controlled, randomised, double-blind study has been made of the acute effects of bunazosin an₁-antagonist, on urinary sodium excretion, atrial natriuretic peptide (ANP), arginine vasopressin (AVP), and the renin-aldosterone system in 7 healthy men.A single oral dose of bunazosin 2.0 mg caused a significant reduction (P < 0.05) in urinary sodium excretion after 0–2 h, 2–4 h, and 4–6 h. The mean values for plasma ANP, AVP, aldosterone, and cortisol concentrations at those times were similar after placebo and bunazosin, and plasma renin activity was significantly increased 2 and 4 h after bunazosin.Pretreatment with oral enalapril 10 mg, an angiotensin converting enzyme inhibitor, did not prevent the bunazosin-induced reduction in urinary sodium excretion.There was a significant positive correlation between the drug-induced changes in blood pressure and urinary sodium excretion.The results suggest that ANP, AVP, and renin-aldosterone may play little role in the sodium retention caused by acute₁-adrenoceptor blockade in man.