Stimulation by glucose and carbamylcholine of phospholipase A2 in pancreatic islets

Glucose, in high concentrations (16.7-27.8 mM), caused a modest increase in effluent radioactivity from rat pancreatic islets prelabelled with [U-14C] arachidonate. The response to glucose was abolished in the absence of extracellular Ca2+. At a low glucose concentration (5.6 mM), carbamylcholine (1.0 mM) provoked a more marked and sustained increase in effluent radioactivity. The response to the cholinergic agent was abolished in the presence of atropine or absence of extracellular Ca2+. These results suggest that carbamylcholine and, to a lesser extent, glucose cause a Ca2+-dependent activation of phospholipase A2 in intact islet cells.