[14C]-2-deoxyglucose uptake studies in Leydig cells.

The present study examines several aspects of [14C]-2-deoxyglucose uptake by rat Leydig cells: the characteristics of uptake by Leydig cells and type of inhibition by cytochalasin B, the effect of other drugs on [14C]-2-deoxyglucose uptake, the specificity of the glucose transporter for other substrates and the effect of various hormones. The apparent Km and V for [14C]-2-deoxyglucose were 0.4 mM and 0.17 mumol/min/10(6) cells, respectively. The inhibition of [14C]-2-deoxyglucose by cytochalasin B was competitive in nature, with an apparent Ki of 0.28 microM. Both phloretin and phlorizin (1.0-50 microM) inhibited [14C]-2-deoxyglucose uptake in a dose-dependent manner. Although D-glucose inhibited [14C]-2-deoxyglucose uptake by Leydig cells, L-glucose was ineffective, reflecting the stereospecificity of the glucose transporter for the former substrate. Various hormones, including: insulin, LH, 17 beta-estradiol or growth hormone which have been reported to stimulate glucose uptake in cells from other tissues, had no effect on [14C]-2-deoxyglucose uptake in Leydig cells under the current conditions. It remains to be determined how glucose uptake in Leydig cells is regulated.