TRANSLOCATION OF 2 GLUCOSE TRANSPORTERS IN HEART - EFFECTS OF ROTENONE, UNCOUPLERS, WORKLOAD, PALMITATE, INSULIN AND ANOXIA

Our previous studies on the acute regulation of glucose transport in p erfused rat hearts were extended to explore further the mechanism of r egulation by anoxia; to test the effects of palmitate, a transport inh ibitor; and to compare the translocation of two glucose transporter is oforms (GLUT1 and GLUT4). Following heart perfusions under various con ditions, glucose transporters in intracellular membranes were quantita ted by reconstitution of transport activity and by Western blotting. R otenone stimulated glucose uptake and decreased the intracellular cont ents of glucose transporters. This indicates that it activates glucose transport via net outward translocation, similarly to anoxia. However , two uncouplers of oxidative phosphorylation produced little or no ef fect. Increased workload (which stimulates glucose transport) reduced the intracellular contents of transporters, while palmitate increased the contents, indicating that these factors cause net translocation fr om or to the intracellular pool, respectively. Relative changes in GLU T1 were similar to those in GLUT4 for most factors tested. A plot of c hanges in total intracellular transporter content vs. changes in gluco se uptake was roughly linear, with a slope of -0.18. This indicates th at translocation accounts for most of the changes in glucose transport , and the basal pool of intracellular transporters is five times as la rge as the plasma membrane pool.