EFFECTS OF ATRIAL-NATRIURETIC-PEPTIDE ON WATER AND NACL ABSORPTION ACROSS THE INTESTINE

Previous studies have demonstrated that atrial natriuretic peptide (ANP) causes natriuresis and diuresis. However, it is not established whether ANP also alters fluid and electrolyte balance via actions on intestinal absorption of water and sodium chloride. Therefore, the purpose of the present study was to investigate the effects of ANP on water and NaCl absorption across the intestine. First, we determined that ANP was taken up from the intestinal circulation in conscious dogs. During the intravenous infusion of ANP (0.3-mu-g.kg-1.min-1), 27.4% of the ANP delivered to the intestinal vascular bed were removed from the circulation at that vascular bed, whereas only 1% of the ANP delivered to the hepatic circulation was removed at the hepatic vascular bed. Second, we determined the effects of the ANP infusion on splanchnic circulation in conscious dogs. ANP decreased hepatic arterial blood flow by 14%, portal venous blood flow by 16%, total hepatic blood flow by 15%, and cardiac output by 14%. Finally, we studied the effects of ANP on intestinal absorption of water and NaCl. ANP suppressed net absorption of water by 61%, Na+ by 43%, and Cl- by 42% across the jejunum but not the ileum. These results suggest that ANP modulates water and NaCl homeostasis across the jejunum but not across the ileum.