Long-term hypotensive and renal effects of atrial natriuretic peptide

The present study was designed to examine the short-term and long-term effects of increased plasma levels of atrial natriuretic peptide on the glomerular filtration rate, sodium excretion, and arterial pressure. Intravenous infusion of synthetic atrial natriuretic peptide (2 μg/kg/bolus, 50 ng/kg/min continuous infusion) for 45 minutes in six conscious dogs increased plasma levels of immunoreactive atrial natriuretic peptide from 69 ± 10 to 233 ± 14 pg/ml. Short-term increases in plasma levels of atrial natriuretic peptide increased the glomerular filtration rate from 53 ± 15 to 82 ± 16 ml/min and increased sodium excretion from 74.4 ± 32.6 to 146.9 ± 38.1 μq/min. Mean arterial pressure decreased slightly, from 88 ± 3 to 83 ± 3 mm Hg, whereas no changes occurred in plasma renin activity (2.0 ± 0.6 to 1.6 ± 0.8 ng of angiotensin I per milliliter per hour) or plasma aldosterone concentration (6.9 ± 2.3 to 8.1 ± 3.9 ng/dl). To determine whether the short-term effects of atrial natriuretic peptide on the glomerular filtration rate and sodium excretion lead to a sustained reduction in mean arterial pressure, atrial natriuretic peptide (50 ng/kg/min) was infused intravenously for 5 days in six conscious dogs. Long-term infusion increased plasma levels of immunoreactive atrial natriuretic peptide from 27 ± 5 to 292 ± 31 pg/ml. The infusion caused only a transient increase in sodium excretion and had no significant long-term effect on the glomerular filtration rate. Mean arterial pressure decreased from 90 ± 3 to 74 ± 3 and 75 ± 4 mm Hg by Days 4 and 5 of the infusion. Plasma renin activity and aldosterone were unchanged during the infusion, despite the large decrease in arterial pressure. These results demonstrate that short-term increases in plasma levels of atrial natriuretic peptide result in marked increases in the glomerular filtration rate and sodium excretion but only a slight decrease in mean arterial pressure. Long-term elevation of plasma atrial natriuretic peptide, however, results in a greater reduction in arterial pressure without having significant effects on the glomerular filtration rate or sodium excretion.