Effects of prepro-vasoactive intestinal polypeptide-derived peptides on net fluid flux in small intestine of anesthetized rats.

Intravenous infusion of low doses of vasoactive intestinal polypeptide, peptide histidine valine-42, and peptide histidine methionine (and the rat equivalent, peptide histidine isoleucine) into anesthetized rats caused a reduction in net absorption of fluid from the small intestine. Larger doses caused a net fluid secretion. At the same nominal infusion rates, peptide histidine valine-42 appeared to be the most potent. In terms of plasma concentrations achieved, however, vasoactive intestinal polypeptide was approximately six times more active than the other two human peptides. If confirmed in humans, these results would suggest that peptide histidine methionine and peptide histidine valine may be as important as vasoactive intestinal polypeptide in causing the watery diarrhea seen in the Verner-Morrison syndrome in which plasma levels of all three peptides are raised.