Preferential uptake of D-glucose by plasma membranes isolated from human adipose tissue

A sensitive method for the measurement of the stereospecific uptake of D-glucose by plasma membranes isolated from human adipose tissue has been developed. The method is based on the difference in uptake of L-[14C]glucose and D-[3H]glucose as measured by the retention of radioactivity by the membrane preparation collected on Millipore filters. This D-glucose-uptake activity was reversible and did not involve any chemical alteration of the sugar. All uptake activity was lost upon boiling the membrane preparation for 5-10 min. All of the hydroxyl groups of D-glucose appear to be involved in a concerted fashion in the uptake reaction. The D-glucose-uptake activity was shown to be closely associated with glucose transport in adipose cells, since it exhibited the following properties characteristic of this carrier-mediated transport system. (a) The uptake was specific for the D-isomer of glucose. (b) Saturation of D-glucose uptake occurred with increasing concentrations of D-glucose, (c) The uptake activity was inhibited by N-ethylamleimide and phloretin, two reagents previously reported to inhibit D-glucose transport. We conclude that plasma membranes isolated from human adipose tissue retain the glucose transport activity of the intact cells and can be used in subsequent attempts at the isolation and characterization of this transport system.