Effects of antiserum against alpha-rat atrial natriuretic peptide in anesthetized rats

Although synthetic atrial natriuretic peptide is known to increase urinary volume and sodium excretion and to reduce arterial blood pressure, the physiological role of endogenous atrial natriuretic peptide is still unclear. We investigated the effects of specific rabbit antiserum against alpha-rat atrial natriuretic peptide on hemodynamics, diuresis, and natriuresis in anesthetized rats. A significant rise in mean blood pressure lasted for about 60 minutes after intravenous administration of the antiserum, with the maximal increment being approximately 7%. Similarly, a significant increase in cardiac output was obtained 20 minutes after injection at an increment of approximately 11%. Heart rate, however, remained unchanged. On the other hand, significant reductions in urine output and urinary sodium and potassium excretion lasted for about 20 minutes after administration of the antiserum, with maximal decrements being 63%, 63%, and 60%, respectively. No significant effects on hemodynamics, diuresis, and natriuresis were observed following injection of normal rabbit serum. These results indicate that endogenous atrial natriuretic peptide has an important physiological role in the regulation of hemodynamics and water-electrolyte balance.