Time course studies of glucose-induced changes in glucose-6-phosphate and fructose-1, 6-diphosphate content of mouse and rat pancreatic islets

Abstract

The concentrations of glucose 6-phosphate (G6P) and fructose 1-6-diphosphate plus triose-phosphates (FDP + TPs) were measured in isolated islets of Langerhans from mice and rats after a sudden increase in extracellular glucose concentration from 0.5 to 3.4 mg/ml. In mouse islets, the contents of G6P and (FDP + TPs) were both raised after a two minute incubation at the high glucose concentration and remained elevated for at least 30 min. In rat islets, the G6P but not the (FDP + TPs) content was increased after a 5 min exposure to high glucose. After a 30 min incubation, both G6P and (FDP + TPs) contents were higher than at low glucose concentration. The (G6P)/(FDP + TPs) ratio was some tenfold higher in mouse islets than in rat islets. Increasing extracellular glucose concentration was associated with an increase in the (G6P)/(FDP + TPs) ratio. The results are consistent with the increased glycolytic rate in response to a raised extracellular glucose concentration arising primarily from an increase in the rate of phosphorylation of glucose, and with the hypothesis that the insulin secretory response to glucose may be mediated by a metabolite of the sugar. © 1973 Springer-Verlag.