Glycolysis and the Pasteur Effect in Rat Reticulocytes*

Under aerobic conditions, glucose consumption by rat reticulocytes was relatively low. When cellular respiratory activity was blocked by antimycin A, both glucose uptake and lactate formation were greatly increased. Pasteur control (the ratio of the rate of glycolysis in the respiratoryinhibited state to that in the uninhibited aerobic state) was very high in these cells and varied from 9 to 12. A crossover plot of the concentrations of glycolytic intermediates in the respiratory-inhibited cell as percentages of the control values showed forward crossovers at the phosphofructokinase and pyruvate kinase steps and a reversed crossover at the phosphoglyceromutase step. A third forward crossover at the 3-phosphoglycerate kinase step was suggested by an increase in the steady state concentration of 3-phosphoglycerate in the respiratory-inhibited state. Uncoupling of mitochondrial oxidative phosphorylation by D-trifluoromethoxy-carboxycyanide phenylhydrazone (FCCP) increased the rate of glycolysis, but this was further increased after the addition of antimycin A. The ratio of the rate of glycolysis in cells treated with antimycin A to that in cells treated with FCCP varied from 1.5 to 2.0. Oxidative utilization of glucose through mitochondrial activity in these cells was very low and accounted for about 6% of the total glucose utilized in .the aerobic regulated state; in the uncoupled state this value rose to only about 12 %. Rat reticulocytes utilized glycerol to support glycolysis and a high Pasteur control was maintained with this substrate. This demonstrates that there is strong regulation of glycolysis beyond the phosphofructokinase step. Glycerol j-phosphate was found in these cells when glycerol was the added substrate but was absent when glucose was the added substrate. This demonstrates the presence of glycerokinase in rat reticulocytes.