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 on 86Rb+ efflux, 45Ca2+ uptake, electrical activity and second messenger systems of isolated mouse islets. Vasoactive intestinal polypeptide enhanced insulin release and 45Ca2+ 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 of 86Rb+ 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.