Comparison of pancreatic responses to portal and systemic secretin and VIP in cats.

This study was designed to compare pancreatic bicarbonate responses to secretin and vasoactive intestinal peptide (VIP) administered either by peripheral or portal route in 24 anesthetized cats. Continuous intravenous infusion of graded doses of secretin (rang from 0.04 to 0.68 nmol/kg per h), stimulated pancreatic volume flow and bicarbonate outputs dose dependently and not statistically differently when given into the peripheral or portal vein. VIP infused in graded doses (range from 0.60 to 9.62 nmol/kg per h) into the peripheral vein produced pancreatic volume flow and bicarbonate outputs not statistically different from those obtained with secretin. In contrast, the biological activity of VIP administered intraportally was reduced by 60% at lower VIP doses (0.60 and 1.20 nmol/kg per h) and by 40% at 2.40 nmol/kg per h, whereas at higher doses it was not significantly changed. This study provides evidence that VIP in the cat is a secretin-like full agonist of pancreatic bicarbonate secretion and that it is only partially inactivated by the liver.