GLYCOLYSIS AND ENERGY-METABOLISM IN RAT-LIVER DURING WARM AND COLD ISCHEMIA - EVIDENCE OF AN ACTIVATION OF THE REGULATORY ENZYME PHOSPHOFRUCTOKINASE

The current study was undertaken so that the effects of both ischemia and ischemia + hypothermia could be examined in mammalian liver. Parti cular reference was made to the function of glycolysis, which is the o nly mechanism for energy production under these conditions. The respon se of adenylate pools reflected the energy imbalance created during wa rm ischemia within minutes of organ isolation. ATP levels and energy c harge values for control (freshly isolated) livers were 1.20 +/- 0.07 and 0.49 +/- 0.02 mu mol/g. Within 5 min of warm ischemia, ATP levels had dropped well below control values and by 30 min warm ischemia, ATP , AMP, and E.C. values were 0.21, 2.01, and 0.17 mu mol/g, respectivel y. Cold ischemic livers (flushed with Marshall's citrate solution and stored on ice) exhibited similar, but more protracted, patterns of ade nylate depletion (ATP and ADP) and accumulation (AMP). In both warm an d cold ischemic livers, levels of fructose-6-phosphate (F6P) and fruct ose-1,6-bisphosphate (F1,6P(2)) indicated a marked activation of glyco lysis at the phosphofructokinase (PFK) locus after a certain time of i schemia. Although the activations occurred at different times (30 min and 10 h for warm and cold ischemic livers, respectively), the pattern s of change in levels of glycolytic metabolites associated with the PF K-catalyzed reaction were similar; levels of F6P dropped and F1,6P(2) increased. Changes in metabolite levels (phosphoenol pyruvate and pyru vate) associated with another key suspect regulatory enzyme, pyruvate kinase, indicated no role in regulatory control of glycolysis during w arm or cold ischemia. The activation of PFK at 30 min and 10 h of warm and cold ischemia, respectively, may reflect the accumulating effects of loss of intracellular homeostasis, which leads to impending irreve rsible damage. (C) 1994 Academic Press, Inc.