Arachidonic acid induces an increase in the cytosolic calcium concentration in single pancreatic islet beta cells.

The insulin secretagogue D-glucose induces both accumulation of nonesterified arachidonic acid (35 microM) in pancreatic islets and a rise in beta cell cytosolic [Ca++]i. Arachidonate amplifies both voltage-dependent Ca++ entry in secretory cells and depolarization-induced insulin secretion. Here, arachidonate induced a biphasic rise in [Ca++]i of Fura-2AM loaded beta cells which increased with arachidonate concentration (5-30 microM), was reversed upon washout, and was unaffected by the arachidonate oxygenase inhibitor BW755C. The sustained phase of the rise was abolished by removal of extracellular Ca++ and amplified by depolarization with KCl. The accumulation of nonesterified arachidonate in islets stimulated by D-glucose may therefore promote the D-glucose-induced rise in beta cell [Ca++]i.