Progesterone and glucose metabolism in the female rat adipocyte: effect on hexokinase activity

Progesterone decreases the oxidation of 2-deoxyglucose and glucose through the pentose-phosphate pathway in isolated female rat adipocytes and, therefore, the effect of this steroid incubation in vitro, progesterone decreased total hexokinase activity but did not affect the isoenzyme-I activity. Progesterone had no direct effect on fat cell cytosol hexokinase and its action on glucose oxidation was not affected by variations in the concentration of Mg2+, the cofactor of hexokinase. Our data suggest that the decreased activity of hexokinase in the presence of progesterone is due to a decrease in the activity of the insulin-sensitive isoenzyme-II. This results from the steroid acting at a step beyond enzyme activation and may be mediated by a feedback mechanism.