Binding and antilipolytic action of insulin in isolated adipocytes from cortisol-treated rats

The effects of an in vivo cortisol-treatment to rats (2 X 2 mg/rat/day, for one week) on insulin plasma levels, insulin binding and antilipolytic activity in rat adipose tissue were investigated. Hyperinsulinemia together with an increase in insulin degradation in the serum of cortisol-treated rats were observed. The adipocytes from cortisol-treated animals showed a statistically significant decrease in insulin binding but no change in receptor numbers [cortisol-treated 103,000 +/- 8,000 (n = 8) receptors/cell and controls 138,000 +/- 15,000 (n = 16) receptors/cell], together with unchanged receptor affinity [ED50: cortisol-treated 3 X 10(-9) M and controls 3.2 X 10(-9) M], and a decreased sensitivity to the antilipolytic effect of insulin. The evidence presented for pre-receptor, receptor and post-receptor insulin defects on the action of cortisol in isolated rat adipocytes could represent a coordinated mechanism by which cortisol exerts "insulin resistance" in this tissue.