In vivo and in vitro effects of glucocorticoids on glucose transport in human polymorphonuclear leukocytes.

In order to study whether or not exogenous and/or endogenous glucocorticoids affect the glucose transport rate in human cells, we examined the transport rate of a non-metabolizable hexose analogue, 3-O-methyl-D-glucose, in polymorphonuclear leukocytes from patients with hypercortisolism. The mean glucose transport rate was prominently decreased in 5 patients with Cushing's syndrome compared with 29 healthy controls (5.4 +/- 1.8 vs 10.4 +/- 2.5 fl/cell.sec, mean +/- SD, p < 0.001) and the transport rate returned to normal range after adenoma resection in 2 of them. In 10 patients with nephrotic syndrome treated with prednisolone, a significant negative correlation was found between transport rates and daily prednisolone doses. When prednisolone of 40 mg/day was administered to a diabetic patient and the dose was gradually reduced, glucose transport rate was transiently decreased during the initial period. In an in vitro study, a synthetic glucocorticoid, dexamethasone, directly inhibited glucose transport rate in those cells in time- and concentration-dependent manners by mainly reducing Vmax. These results suggest that either exogenous or endogenous hypercortisolism in humans is associated with a decrease in glucose transport rate in polymorphonuclear leukocytes, and that the direct effect of glucocorticoids accounts at least in part for the decreased glucose transport rates found in those cells.