CHANGES IN GLUCOSE TRANSPORTER 2 AND CARBOHYDRATE-METABOLIZING ENZYMES IN THE LIVER DURING COLD PRESERVATION AND WARM ISCHEMIA

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Abstract
In order to examine glucose metabolism in liver grafts during cold preservation (24 and 48 hr), warm ischemia (60 and 120 min), a combination of the two and reperfusion, the amount of protein and mRNA of glucose transporter 2 and the activities of enzymes in glycolysis (glucokinase, phosphofructokinase, pyruvatekinase), gluconeogenesis (glucose 6-phosphatase, fructose 1,6-bisphosphatase), and the pentose phosphate pathway (glucose 6-phosphate dehydrogenase) were measured. It appeared that glucose transport, the pentose phosphate pathway, and gluconeogenesis were maintained during cold preservation and warm ischemia. The activity of glucokinase significantly decreased from the control value of 1.33±0.23 IU/g protein to 0.70±0.17 (24 hr, P<0.05) and 0.57±0.12 (48 hr, P<0.01) only during cold preservation. However, the activity of phosphofructokinase significantly decreased from the control value of 4.37±0.06 IU/g protein to 2.67±0.15 (60 min, P<0.0001) and 1.53±0.06 (120 min, P<0.0001) only during warm ischemia. This indicates that glycolysis deteriorates during both cold preservation and warm ischemia and demonstrates further that the balance between glycolysis and gluconeogenesis shifts to gluconeogenesis. Even when cold preservation was combined with warm ischemia, the activity of glucokinase decreased only during cold preservation and the activity of phosphofructokinase decreased only during warm ischemia. Furthermore, these changes were time-dependent. It is suggested that they can be used as a clock to measure the durations of cold preservation and warm ischemia separately and that the magnitude of an ischemic injury to a liver and a liver graft's viability can be indirectly estimated before transplantation.