Somatostatin activates glibenclamide‐sensitive and ATP‐regulated K+ channels in insulinoma cells via a G‐protein

Abstract

Somatostatin, an hyperglycemia-inducing hormone, was studied in rat insulinoma (RINm5F) cells using ⁸⁶Rb⁺ efflux techniques. ⁸⁶Rb⁺ efflux is stimulated by somatostatin in a dose-dependent manner. The half-maximum value of activation is 0.7 nM. Somatostatin-induced ⁸⁶Rb⁺ efflux is abolished by the hypoglycemia-inducing sulfonylurea, glibenclamide, a known blocker of ATP-regulated K⁺ channels. Somatostatin activation is prevented by pretreatment of insulinoma cells with pertussis toxin. ⁸⁶Rb⁺ efflux studies show that somatostatin activates an ATP-dependent K⁺ channel.