Glucose both inhibits and stimulates insulin secretion from isolated pancreatic islets exposed to maximally effective concentrations of sulfonylureas.

Isolated pancreatic islets from mice were perifused with media containing maximally effective concentrations of glibenclamide (0.1-10 mumol/l) or glipizide (1 mumol/l). In these islets an increase of the glucose concentration from 10 mmol/l to 40 mmol/l or addition of D-glyceraldehyde (20 mmol/l) caused a temporary decrease in insulin release which was followed by a sustained enhancement of release. alpha-Ketoisocaproate (3 or 20 mmol/l) did not inhibit insulin release; at high concentration it was an even stronger secretagogue than D-glucose or D-glyceraldehyde. It is concluded that high energy phosphates couple B-cell fuel metabolism and insulin release by acting both on the ATP-dependent K+ channel and on other targets not yet identified.