| Abstract: | The effects of the hypoglycemic sulfonylureas tolbutamide and glibenclamide on free cytoplasmic Ca2+, Ca2+]i, were compared with that of a depolarizing concentration of K+ in dispersed and cultured pancreatic beta-cells from ob/ob mice. Ca2+]i was measured with the fluorescent Ca2+-indicator quin2. The basal level corresponded to 150 nM and increased to 600 nM after exposure to 30.9 mM K+. The corresponding levels after stimulation with 1 microM glibenclamide and 100 microM tolbutamide were 390 and 270 nM respectively. K+ depolarization increased Ca2+]i more rapidly than either of the sulfonylureas. It is suggested that the increased Ca2+]i obtained after stimulation by sulfonylureas is due to depolarization of the beta-cells with subsequent entry of Ca2+ through voltage-dependent channels. |
