Functional abnormalities of islets of Langerhans of obese hyperglycemic mouse.

Glucose-induced insulin release was studied in vitro with isolated islets of Langerhans obtained from obese hyperglycemic C57Bl/6J-ob/ob (ob/ob) and lean C57Bl/6J-+/+ (control) mice. The threshold concentrations of glucose for insulin release were determined. In addition, the effect of total fast and of chronic food restriction on in vitro insulin release were studied. The following was observed: 1) with fasting, islet volume decreased. Islets obtained from ob/ob mice were larger than control islets, except for the chronic food restricted group. 2) Ob/ob islets were more sensitive to glucose than were controls in that the threshold for glucose-induced insulin release occured at lower glucose concentrations. 3) Fasting for 48 h completely abolished glucose-induced insulin release in control islets, whereas glucose-induced insulin release was maintained in 48-h and 7-day fasted ob/ob islets. 4) The increased glucose sensitivity of the ob/ob islets was maintained despite chronic food restriction.