Post ischemic stimulation of 2-deoxyglucose uptake in rat myocardium:: Role of translocation of glut 4

Myocardial ischemia elicits translocation of the insulin-sensitive glucose transporter GLUT-4 from intracellular membrane stores to the sarcolemma. Because glucose metabolism is of crucial importance for post-ischemic recovery of the heart, myocardial uptake of [H-3]-labeled 2-deoxyglucose and subcellular localization of GLUT-4 were determined during 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. Subcellular localization of GLUT-4 was determined by cell fractionation followed by immunoblotting, After 15 and 60 min of reperfusion uptake of 2-deoxyglucose was significantly higher (91 +/- 9 and 96 +/- 8 nmol/min/g wet weight, respectively) as compared to control Values (65 +/- 1 nmol/min/g wet weight). Ischemia elicited translocation of GLUT-4 to the sarcolemma, which persisted after 15 min of reperfusion. However, after 60 min of reperfusion the subcellular distribution of GLUT-4 was similar to control hearts, In conclusion, reversal of ischemia-induced translocation of GLUT-4 to the sarcolemma is rather slow, possibly facilitating glucose uptake early during reperfusion. However, myocardial uptake and phosphorylation of 2-deoxyglucose remains enhanced late during reperfusion, when pre-ischemic distribution of GLUT-4 is almost completely restored, indicating that additional mechanisms are likely to be involved in post-ischemic stimulation of glucose uptake. (C) 1998 Academic Press Limited.