The release of sPLA, from single mouse pancreatic beta-cells was monitored using a fluorescent substrate of the enzyme incorporated in the outer leaflet of the plasma membrane. Stimulation of beta-cells with agents that increased cytosolic free Ca2+ concentration ([Ca2+](i)) induced a rapid release of sPLA(2) to the extracellular medium. Exogenous sPLA(2) strongly stimulated insulin secretion in mouse pancreatic islets at both basal and elevated glucose concentrations. The stimulation of insulin secretion by sPLA(2) was mediated via inhibition of ATP-dependent K+ channels and an increase in [Ca2+]i. Measurements of cell capacitance in single beta-cells revealed that sPLA, did not modify depolarisation-induced exocytosis. Our data suggest that a positive feedback regulation of insulin secretion by co-released sPLA(2) is operational in pancreatic beta-cells and point to this enzyme as an autocrine regulator of insulin secretion. (C) 2003 Elsevier Inc. All rights reserved.