CONTROL OF AEROBIC GLYCOLYSIS IN GUINEA‐PIG CEREBRAL CORTEX SLICES

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Abstract
—The effect of glutamate on aerobic glycolysis in guinea‐pig cerebral cortex slices was analysed in comparison with that of high‐potassium. In contrast to the increased glycolysis in 50 mm‐potassium medium which was accompanied by increases of fructose diphosphate and triose phosphates in the slices, the addition of 5 mm‐d‐glutamate to the medium increased the rate of glycolysis without increasing these intermediates. When increasing the concentration of potassium in the medium up to 20 mm, the rate of aerobic glycolysis was not increased although fructose diphosphate and triose phosphates in the slices were increased. At this potassium concentration in the medium ATP in the slices was highest. At 30 mm‐potassium the rate of glycolysis was increased significantly, but fructose diphosphate and triose phosphates were decreased. ATP was lower at 30 mm‐ than at 20 mm‐potassium. By increasing potassium to 40 mm and above, the rate of glycolysis was further increased, and fructose diphosphate and triose phosphates were again increased. Between 5 and 20 mm‐potassium in the medium the increasing effect of glutamate on glycolysis was very pronounced. d‐Glutamate decreased the amounts of ATP, fructose diphosphate and triose phosphates at any concentration of potassium in the medium. When adding cyclic AMP and 5′AMP to the slices, fructose diphosphate and triose phosphates were increased, but the rate of glycolysis was not increased. On the basis of these observations mechanisms of the control over glycolysis in guinea‐pig cerebral cortex slices are discussed. It is suggested that the glycolysis is controlled by the changes in ATP concentration through their action on the glyceraldehyde 3‐phosphate dehydrogenase and phosphoglycerate kinase system. The changed patterns of the glycolytic intermediate profile in the slices when adding ATP to the medium are consistent with this suggestion. The addition of l‐phenylalanine to guinea‐pig cerebral cortex slices did not inhibit the rate of glycolysis, although it inhibited the activity of pyruvate kinase.