Natriuretic activity of human and monkey atria

Recent evidence indicates that mammalian atria contain a substance that produces a rapid onset natriuresis in anesthetized rats. In the present experiments, small portions of human right atria obtained from patients undergoing coronary bypass surgery, as well as monkey atria and ventricles obtained from the Regional Primate Center, Seattle, were boiled or acid extracted and lyophilized. These materials (30 mg/kg) were dissolved in Ringer's lactate and injected intravenously into anesthetized monkeys to determine their effects on renal function. Their effects were also compared with those of furosemide (0.1 mg/kg) and chlorothiazide (10 mg/kg). Human and monkey atrial extracts produced significant increases in sodium and calcium excretion that were independent of changes in creatinine clearance. Monkey ventricular extract had no consistent renal effects. Furosemide, but not chlorothiazide, mimicked the renal responses to human and monkey atrial extracts in terms of time of onset, duration, and pattern of electrolyte excretion. These data suggest that primate atrial tissue contains a heat- and acid-stable natriuretic factor similar to that first described in the rat, suggesting that mammalian atrial natriuretic factors are cross-reactive among species. In addition, atrial natriuretic factors may have a mechanism of action similar to that of furosemide.