A method for quantifying insulin sensitivity in vivo in the anesthetized rat: the euglycemic insulin clamp technique coupled with isotopic measurement of glucose turnover.

The euglycemic insulin clamp technique coupled with isotopic measurement of the glucose utilization rate ([3-3H] glucose), described previously in man, has been adapted to characterize and quantify insulin sensitivity in vivo in the rat. Only 30 min were needed for the exogenous glucose infusion rate, the specific activity of [3-3H] glucose and the plasma insulin to reach a steady-state value. During the next 30 min of the experiment, blood glucose was maintained at a constant basal level with a coefficient of variation of 2.3%. Plasma insulin was 48 +/- 4 microU/ml and glucose utilization was 1.84 +/- 0.07 mg/min in anesthetized female rats in the basal state. During euglycemic insulin clamp, plasma insulin was 302 +/- 24 microU/ml, glucose utilisation was increased by 53 +/- 10% and endogenous glucose production was decreased by 76 +/- 3%. By studying several insulin concentrations in different groups of rats, we hope to be able to characterize insulin resistance during pregnancy and to determine whether hepatic or peripheral tissues are responsible for this insulin resistance.