Extracellular Calcium and Acetylcholine-stimulated Insulin Secretion

The importance and possible involvement of extracellular calcium in the stimulation of insulin secretion by acetylcholine was examined in the isolated perfused dog pancreas. Acetylcholine (SO μM) failed to stimulate insulin secretion when calcium was omitted from the perfusion medium. In the presence of tetracaine (1 mM) and magnesium (10.16 mM), conditions favoring blockade of Ca⁺⁺ influx into the beta cell, acetylcholine-induced (50μM) insulin secretion was inhibited. We conclude from these observations that acetylcholine-stimulated insulin secretion is dependent upon extracellular Ca⁺⁺ and an increase in Ca⁺⁺ influx may be involved in this stimulation.