Dexamethasone inhibition of hydrogen peroxide-stimulated glucose transport.

Although an action of corticosteroids to inhibit glucose transport is well known, the mechanism by which this is brought about has been unclear. Some evidence has suggested an action on insulin receptors, but a postbinding or postreceptor effect has also been reported. As hydrogen peroxide acts at a postbinding site to stimulate glucose transport, studies were carried out in 3T3-L1 fibroblasts to determine whether corticosteroids would inhibit hydrogen peroxide-induced glucose transport. In this cell type, both insulin and hydrogen peroxide produced a marked increase in glucose transport after a 30-min incubation. The increase produced by hydrogen peroxide, as well as insulin, was inhibited by previous incubation of the cells with dexamethasone. These findings give further support to the conclusion that dexamethasone has effects on glucose transport at a postbinding site. As changes in membrane lipids influence the movement and/or activity of glucose transporters, and dexamethasone alters membrane lipids, dexamethasone-induced changes in the lipids of the plasma membrane may be important in the mediation of the steroid effect upon glucose transport.