Distinct effects of acetylcholine and glucose on 45calcium and 86rubidium efflux from mouse pancreatic islets

The similarities between the effects of acetylcholine and glucose on phospholipid metabolism in pancreatic islet cells prompted the comparison of their effects on ionic fluxes. Acetylcholine (1 μM) consistently increased 45Ca 2+ efflux from mouse islets, whereas glucose increased it in the presence, but decreased it in the absence of extracellular Ca 2+. Acetylcholine consistently accelerated 86Rb + efflux, and this effect was augmented by Ca 2+ omission. On the other hand, glucose markedly inhibited 86Rb + efflux, except when its concentration was raised from 10 to 15 mM in the presence of Ca 2+. Unlike their effects on phospholipid metabolism, the ionic effects of the two insulin-secretagogues are thus very different.