Inhibitory effects of exogenous insulin on oxidative utilization of glucose in septic rats

The influence of exogenous insulin on oxidation of U-14C-glucose was investigated by monitoring the production of 14CO2 in septic rats. Ten Wistar rats underwent ligation of the distal third of the caecum and the ligated caecum was punctured with a 21-G needle (septic rats: group S). A group of ten rats was not subjected to these procedures (control rats: group C). Both groups received parenteral nutrition (PN) for the subsequent 27 hours. Non-protein nutrients were provided exclusively as glucose. Five rats in each group received insulin at a rate of 0.64 U/kg/hr for the last six hours of PN, and these rats were designated groups CI and SI. At the 21st hour of PN, 1.563 muCi of U-14C-glucose was injected as a bolus, and the production of 14CO2 was measured. The cumulative production of 14CO2 for the subsequent six hours, given as a percentage of the 14C injected, was 78.22 +/- 6.22% in group C, 86.16 +/- 4.23% in group CI, 62.38 +/- 13.00% in group S, and 54.38 +/- 6.89% in group SI. The elevated levels of blood glucose in rats in group S were reduced by the administration of insulin. These results indicate that the reduction of elevated blood glucose levels by exogenous insulin in the septic rats with antecedent hyperinsulinemia does not reflect an increase in the oxidative utilization of glucose but rather inhibition of the oxidation of glucose.