Effect of hyperglycemia on the hexose monophosphate shunt in islets of Langerhans.

Abstract

The activities of glucose-6-P dehydrogenase, 6-P-gluconate dehydrogenase, ribulose-5-P epimerase, ribulose-5-P isomerase, transketolase and transaldolase were measured in frozen dried specimens of the islets of Langerhans and exocrine cells of the pancreas. Activities of all five enzymes were comparable in the two cell types. The effect of hyperglycemia on the concentration of 6-P-gluconate was also studied. A ten-fold increase in bloodglucose concentration resulted in a thirteen-fold increase in 6-P-gluconate levels in islet tissue but no change in the exocrine portion of the pancreas. The rate of increase of 6-Pgluconate in the islets during hyperglycemia was slower than the rate of increase of either glucose or glucose-6-P. The rise of 6-P-gluconate appears to be too slow a process to serve as a trigger for the insulin release mechanism.