Glucose-stimulated efflux of fura-2 in pancreatic beta-cells is prevented by probenecid

Fura-2 loaded pancreatic beta-cells, isolated from obese hyperglycemic mice, were studied with respect to cytoplasmic free Ca2+ concentration ([Ca2+]i), insulin release and efflux of indicator. In the absence of glucose there was a continuous efflux of fura-2, which was markedly increased by stimulation with a high concentration of the sugar. Probenecid both reduced basal efflux of fura-2 and prevented that promoted by glucose. There was no interference of the drug with glucose-induced either insulin release or rise in [Ca2+]i. When applying fura-2 in pancreatic beta-cells, the use of probenecid markedly improves the measurements of [Ca2+]i.