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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.

Type

Journal article

Journal

FEBS Lett

Publication Date

07/10/1985

Volume

190

Pages

21 - 24

Keywords

Aminoquinolines, Animals, Calcium, Cytoplasm, Female, Fluorescent Dyes, Glyburide, Hypoglycemic Agents, Ion Channels, Islets of Langerhans, Male, Mice, Mice, Obese, Potassium, Sulfonylurea Compounds, Tolbutamide