Effect of glucocorticoid hormones on fatty acid mobilization and re-esterification in rat adipose tissue.

1. The effect of dexamethasone and cortisol on fatty acid mobilization and re-esterification has been studied in intact adipose tissue and isolated fat cells of the rat. 2. Dexamethasone added in vitro inhibited both the re-esterification of mobilized free fatty acids and the esterification of palmitate in the medium. 3. Under several conditions (low concentrations of dexamethasone, cortisol at a high concentration, with tissue from starved animals), steroid-induced release of free fatty acids could be accounted for by decreased re-esterification only, overall lipolytic activity remaining unmodified. At higher concentrations of dexamethasone, however, stimulation of lipolytic activity also occurred. 4. Decreased re-esterification produced by dexamethasone was observed in the total absence of glucose from the incubation medium. Further, dexamethasone stimulated the disappearance of prelabelled [(14)C]glycogen from the tissue. 5. The evidence presented suggests that mobilization of free fatty acids induced by glucocorticoid hormones under physiological conditions is primarily due to a decrease of the re-esterification rate rather than to lipase activation.