Glucocorticoids and insulin but not growth hormone modulate insulin binding to adipocyte membranes from sheep

Mechanisms by which the glucocorticoid analogue dexamethasone and growth hormone modulate insulin action in sheep adipose tissue have been investigated. Maintenance of sheep adipose tissue in culture for 48 hr in the absence of exogenous hormones resulted in a decrease in insulin binding to adipocyte membranes; this was prevented by the inclusion of 10 nM dexamethasone during culture. Tissue culture for 48 hr with insulin itself decreased insulin binding to adipocyte membranes, whereas tissue culture with growth hormone had no effect on insulin binding. Neither dexamethasone nor growth hormone altered the ability of insulin to decrease insulin binding to its receptor. The study shows that the insulin-antagonistic effects of growth hormone on sheep adipose tissue metabolism are due to an effect subsequent to insulin binding to its receptor, whereas some of the effects of dexamethasone may be due to an increase in the insulin-binding capacity of membranes.