Vasoactive intestinal polypeptide-augmented insulin release: actions on ionic fluxes and electrical activity of mouse islets

Vasoactive intestinal polypeptide is a pancreatic neurotransmitter which augments insulin release. To obtain more detailed information on its mode of action on the pancreatic beta cell we studied the effect of vasoactive intestinal polypeptide on86Rb+ efflux,45Ca2+ uptake, electrical activity and second messenger systems of isolated mouse islets. Vasoactive intestinal polypeptide enhanced insulin release and45Ca2+ uptake in a concentration-dependent manner, and was effective at non-stimulatory and stimulatory glucose levels. It increased glucose-induced electrical activity but was without effect on either glucose-mediated changes of86Rb+ efflux, cAMP or inositol-1,4,5-trisphosphate content. It is suggested that vasoactive intestinal polypeptide augments insulin release by increasing the uptake of Ca2+ into the cell by as yet undefined mechanisms.