Rapid increase in the insulin sensitivity of rat adipocytes after intravenous glucose administration.

To study the mechanism underlying the enhancement of insulin action after carbohydrate challenge, rats were given an iv infusion of 100 mg glucose or saline. Adipocytes were isolated 1, 2, and 3 h after the infusions, and their ability to respond to insulin was examined. Two and 3 h postglucose, the cells showed a 50% increase in insulin sensitivity, as measured by glucose incorporation into total lipid and 2-deoxyglucose uptake. The effect was characterized by a leftward shift in the insulin dose-response curve. There was no change in maximum insulin stimulation. Insulin binding by the fat cells and by liver plasma membranes was not altered by glucose administration. These results demonstrate the presence of a physiological process that acutely enhances the insulin sensitivity of rat adipocytes after iv glucose infusion.