STIMULATED GLUCOSE-UPTAKE IN THE ISCHEMIC BORDER ZONE - ITS DEPENDENCE ON GLUCOSE-UPTAKE IN THE NORMALLY PERFUSED AREA

During acute regional myocardial ischemia, a ''border zone'' exists wh ere the spatial distributions of blood Row and substrate uptake show g radual changes. We investigated the relationship between blood flow an d glucose uptake in the border zone during acute regional ischemia. Me thods: Newly developed quantitative autoradiography using imaging plat es and two long-lived radioisotopes was applied to rat hearts subjecte d to 30 min of left coronary artery occlusion, Blood flow, glucose upt ake and fatty acid uptake was assessed with 4-[N-methyl-C-14]iodoantip yrine, 2-deoxy-D-[1-H-3]glucose (H-3-DG) and beta-methyl[1-C-14]heptad ecanoic acid (C-14-BMHDA), respectively. Results: In rats showing H-3- DG uptake in the normally perfused area (Norm) of 254 +/- 96 Bq/mg (hi gh-DG) and 56 +/- 20 Bq/mg (low-DG) (n = 4 for each), H-3-DG uptake in the border zone was 148 +/- 52 Bq/mg and 58 +/- 15 Bq/mg (p < 0.05 hi gh-versus low-DG), respectively. The relationship between blood flow a nd H-3-DG uptake in the border zone was altered by the different H-3-D G uptake levels in Norm, In high-DG, H-3-DG uptake in the border zone was reduced significantly according to the decrease in the percentage of blood flow, However, in low-DG, no significant differences in H-3-D G uptake were found among the regions in the border zone with differen t levels of the percentage of blood Row, except in the region with 10% -19% of the percentage of blood flow, In the border zone, the percenta ge of H-3-DG uptake per unit blood flow normalized to that in Norm inc reased according to the decrease in the percentage of blood flow, and this increase was steeper in low-DG than in high-DG (p < 0.0005), The percentage of C-14-BMHDA uptake was lower than the percentage of H-3-D G uptake (27 +/- 3% versus 78 +/- 18% of that in Norm, p < 0.0005) in the peripheral ischemic area. Conclusion: The relationship between blo od flow and glucose uptake in the ischemic border zone was altered by the different glucose uptake levels in Norm. Glucose uptake in the bor der zone was higher in rats with higher glucose uptake levels in Norm, suggesting that glucose uptake in the border zone stimulated by ische mia can be accelerated still more by humoral factors.