Angiotensin II regulates the metabolism but not the secretion of vasoactive intestinal peptide in the rabbit.

Abstract

1. We have previously demonstrated that the metabolism and secretion of vasoactive intestinal peptide are affected by both acute and chronic dietary sodium. Sodium concentrations in portal and systemic plasma were unaffected by differing levels of sodium intake or administration of an acute gastric sodium load. We sought, therefore, to determine whether other hormones involved in sodium homoeostasis (such as angiotensin II) might be involved in regulating the metabolism and secretion of vasoactive intestinal peptide. We determined the metabolic clearance rate and theoretical secretion rate of vasoactive intestinal peptide in rabbits on low sodium (high circulating angiotensin II) and high sodium (low circulating angiotensin II) diets with and without simultaneous angiotensin II infusion. 2. The metabolic clearance rate of vasoactive intestinal peptide was significantly higher in rabbits on the high sodium diet during both vehicle control (P < 0.01) and angiotensin II (P < 0.05) infusion. Angiotensin II infusion decreased the metabolism of vasoactive intestinal peptide in rabbits on both low (P < 0.01) and high (P < 0.01) sodium diets. 3. Although there was a significant difference in secretion rates between the two dietary groups (P < 0.025) under basal conditions, infusion of angiotensin II did not alter the secretion rate significantly in either group. 4. We conclude that angiotensin II regulates the metabolism of vasoactive intestinal peptide in the rabbit, but does not regulate its secretion.