Effects of glibenclamide and tetracaine on 86Rb+ fluxes in mouse pancreatic beta-cells.

Potassium transport was measured in beta-cell-rich islets from ob/ob-mice using the K+-analogue 86Rb+. Both tetracaine (0.1 mM) and glibenclamide (0.1 microM) reduced the ouabain-resistant 86Rb+ influx but did not significantly affect the ouabain-sensitive portion (Na+/K+ pump). Tetracaine (0.5 - 1 mM) or glibenclamide (0.2 mM) decreased the 86Rb+ equilibrium content and glibenclamide (1 microM) transiently reduced the 86Rb+ efflux rate but 0.1 mM tetracaine had only a slight effect on this flux rate. The results suggest that a change in ouabain-resistant (passive) K+ fluxes, but not the Na+/K+ pump, is involved in stimulation of insulin secretion by glibenclamide and tetracaine. Both drugs may exert similar effects on the beta-cell plasma membrane.