Decreased insulin binding of human erythrocytes after dexamethasone or prednisone ingestion.

We have investigated changes in insulin binding in erythrocytes in response to overnight ingestion of 1 mg dexamethasone or 10 mg of prednisone in two groups of eight lean, healthy subjects. Dexamethasone administration reduced insulin binding from 9.6 to 6.8% (P < 0.001) with concomitant increase in basal plasma insulin from 10.5 to 14.1 microU/ml (P < 0.05). Prednisone ingestion reduced insulin binding from 9.9 to 7.9% (P < 0.01), but the increase in basal insulin from 16.9 to 20.6 microU/ml was not significantly different. The decrease in insulin binding with both dexamethasone and prednisone was associated with decreased affinity of erythrocyte for insulin at low occupancy and the increase in the dose of unlabeled insulin resulted in 50% inhibition of specific binding without changes in the number of receptors. The earliest decrease in insulin binding was noted within 2 h after ingestion of 1 mg of dexamethasone. These data suggest that acute alteration of insulin receptor function could occur in erythrocytes by small amounts of dexamethasone or prednisone through a mechanism consistent with a decrease in receptor affinity rather than a decrease in the number of receptors.