Effect of endothelin-1 and vasoactive intestinal contractor on blood flow and output of vasoactive intestinal polypeptide in the feline colon.

Overview

Injection of the structurally related peptides, endothelin-1 and vasoactive intestinal contractor (VIC), into a branch of the superior mesenteric artery in anesthetized cats caused dose-dependent reductions in blood flow in the portal vein and inferior mesenteric artery. The maximum effect occurred after 1 minute and was more prolonged in the portal vein. The effects of the two peptides were not significantly different. The colonic output of vasoactive intestinal polypeptide (VIP) into portal venous blood was decreased significantly by endothelin-1 and VIC, returning to baseline more rapidly than blood flow. When norepinephrine was injected to produce comparable reductions in blood flow, the output of VIP into portal venous blood was not altered significantly. These results suggest that inhibition of output of the vasodilator VIP contributes to the vasoconstrictor effects of endothelin-1 and VIC in the feline colonic vascular bed.