Dissociation of glucocorticoid inhibition of glucose transport and metabolism by increase in adipocyte age and/or size.

Exposure of adipocytes from young rats (2--3 months old) to dexamethasone in vitro results in 40--50% inhibition of glucose transport and metabolism. Comparable experiments with older rats reveal that the hormonal effect on glucose metabolism is progressively reduced to about 20% in 12- to 13-month-old animals and about 5% in 24- to 26-month-old animals. However, no effect of dexamethasone on the glucose transport system can be detected in either of the older age groups when three different sugars are used to measure transport activity. The ability of dexamethasone to inhibit glucose phosphorylation seems to be closely related to inhibition of overall glucose oxidation in both young and old adipocytes. That the membrane may be generally more resistant to control of glucose transport is suggested by failure or reduced ability of insulin, vitamin K5, and hydrogen peroxide to stimulate this function in older cells.