Studies on the secretion, metabolism and action of atrial natriuretic peptide in man

Radio-immunoassay of atrial natriuretic peptide (ANP) and infusions of alpha-human ANP (alpha-hANP) have been used to study the secretion, metabolism, regulation and actions of ANP in man. Plasma immunoreactive ANP (irANP) was twice as high in arterial blood as in simultaneously sampled venous plasma from the femoral, hepatic and renal vein, but no arteriovenous difference was found across the lung. Analysis of plasma extracts by high performance liquid chromatography confirmed that alpha-hANP-like material was a major component in coronary sinus and peripheral arterial and venous plasma. In normal subjects, venous plasma irANP was increased by both acute and chronic sodium loads, and by exercise. The cardiac secretion of irANP, and peripheral venous levels, were markedly increased by atrial pacing in four patients investigated for arrhythmia. Plasma irANP concentrations were elevated in many patients with circulatory disorders, including chronic renal failure, congestive heart failure and during spontaneous tachyarrhythmias. Constant 60-min intravenous infusions of alpha-hANP increased urinary sodium excretion in normal subjects, under conditions of both high- and low-sodium intake, and selectively reduced plasma aldosterone concentrations. These effects were observed at the venous levels of plasma irANP found in some patients with circulatory disease. Taken together, the present studies suggest that ANP has important endocrine functions in human health and disease.