Hexose metabolism in pancreatic islets: time-course of the oxidative response to D-glucose.

The time-course for the generation of 3HOH from D-[5-3H]glucose and for the production of 14CO2, 14C-labelled acidic metabolites and radioactive amino acids from D-[3,4-14C]glucose, D-[2-14C]glucose and D-[6-14C]glucose was monitored, over 60 to 120 min incubation, in both rat pancreatic islets and parotid cells exposed to a low or high concentration of the hexose. In islets stimulated by D-glucose, a progressive increase in the oxidation rate of glucose-derived acetyl residues was observed. Such a phenomenon was not observed in islets exposed to a low concentration of D-glucose, concerned specifically the oxidation of acetyl residues in the Krebs cycle as distinct from their generation in the reaction catalyzed by pyruvate dehydrogenase, and failed to occur in parotid cells. It is concluded that the increase in the oxidation rate of glucose-derived acetyl residues found in pancreatic islets represents an unusual phenomenon not encountered in other cell types and specifically regulated in terms of its time-course, concentration dependency and relationship to other oxidative events.