POST ISCHEMIC STIMULATION OF 2-DEOXYGLUCOSE UPTAKE IN RAT MYOCARDIUM - ROLE OF TRANSLOCATION OF GLUT-4

Myocardial ischemia elicits translocation of the insulin-sensitive glu cose transporter GLUT-4 from intracellular membrane stores to the sarc olemma. Because glucose metabolism is of crucial importance for post-i schemic recovery of the heart, myocardial uptake of [H-3]-labeled 2-de oxyglucose and subcellular localization of GLUT-4 were determined duri ng reperfusion in isolated rat hearts perfused with medium containing 0.4 mM palmitate and 8 mM glucose. Hearts were subjected to 20 min of no-flow ischemia, followed by reperfusion for up to 60 min. Subcellula r localization of GLUT-4 was determined by cell fractionation followed by immunoblotting, After 15 and 60 min of reperfusion uptake of 2-deo xyglucose was significantly higher (91 +/- 9 and 96 +/- 8 nmol/min/g w et weight, respectively) as compared to control Values (65 +/- 1 nmol/ min/g wet weight). Ischemia elicited translocation of GLUT-4 to the sa rcolemma, which persisted after 15 min of reperfusion. However, after 60 min of reperfusion the subcellular distribution of GLUT-4 was simil ar to control hearts, In conclusion, reversal of ischemia-induced tran slocation of GLUT-4 to the sarcolemma is rather slow, possibly facilit ating glucose uptake early during reperfusion. However, myocardial upt ake and phosphorylation of 2-deoxyglucose remains enhanced late during reperfusion, when pre-ischemic distribution of GLUT-4 is almost compl etely restored, indicating that additional mechanisms are likely to be involved in post-ischemic stimulation of glucose uptake. (C) 1998 Aca demic Press Limited.