6-Phosphogluconate/glucose-6-phosphate ratio in rat pancreatic islets during inhibition of insulin release by exogenous insulin.
Inhibition of glucose-stimulated insulin release by exogenous insulin has been demonstrated in pancreatic islets to be associated with a decrease of the NADPH/NADP ratio and the pentose-phosphate cycle activity. Batches of five islets were incubated for 15 and 90 minutes in 1 ml. of KRB buffer with 2 per cent albumin containing 3 mg./ml. glucose and 0, 200, 400, or 800 microU./ml. of rat insulin, and the glucose-6-phosphate (G6P) and 6-phosphogluconate (6PG) contents were determined by enzymatic cycling. In response to a rise in the concentration of insulin, the 6PG/G6P ratio decreased. A close relationship was observed between this decrease of 6PG/G6P ratio and the net insulin release, the absolute rate of glucose oxidation via the pentose phosphate cycle, and the NADPH/NADP ratios measured under similar conditions. The results suggest that exogenous insulin, directly or indirectly, regulates the pentose cycle activity in the pancreatic islets at the G6P dehydrogenase step.
D000818:Animals; D002245:Carbon Dioxide; D005260:Female; D005942:Gluconates / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D005958:Glucosephosphates / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010428:Pentosephosphates / Q000378:metabolism; D051381:Rats
D005942:Gluconates; D005958:Glucosephosphates; D007328:Insulin; D010428:Pentosephosphates; D009243:NAD; D002245:Carbon Dioxide; D009249:NADP; D005947:Glucose