The pH-dependence of sugar-transport and glycolysis in cultured Ehrlich ascites-tumour cells.
1. pH-dependence of glycolysis has generally been ascribed to the effects of pH on the activities of glycolytic enzymes. The present study shows that sugar transport is pH-dependent in cultured Ehrlich ascites-tumour cells. 2. The rates of glucose consumption, of 3-O-methylglucose transport, and of 2-deoxyglucose transport and phosphorylation increased as linear functions of pH, as the pH of the cell culture medium was increased from 6.1 to 8.5. Transport of glucose, as measured in ATP-depleted cells, was pH-dependent to the same extent as transport of the non-metabolizable sugars. 3. Glucose consumption rates were about 8-fold higher at pH 8.5 than at pH 6.4. About 65-85% of glucose was converted into lactate. Sugar transport rates were 2.5-fold higher at pH 8.5 than at pH 6.3. 4. pH affected both simple diffusion and facilitated diffusion. pH effect was mainly on the Vmax. of 2-deoxyglucose uptake, and on the rapid-uptake phase of 3-O-methylglucose transport. 5. It was estimated that about 70% of the pH effect on the rates of glucose consumption may be due to the effect on sugar transport and the remainder to the effect on the activities of glycolytic enzymes.
The pH-dependence of sugar-transport and glycolysis in cultured Ehrlich ascites-tumour cells. 1. pH-dependence of glycolysis has generally been ascribed to the effects of pH on the activities of glycolytic enzymes. The present study shows that sugar transport is pH-dependent in cultured Ehrlich ascites-tumour cells. 2. The rates of glucose consumption, of 3-O-methylglucose transport, and of 2-deoxyglucose transport and phosphorylation increased as linear functions of pH, as the pH of the cell culture medium was increased from 6.1 to 8.5. Transport of glucose, as measured in ATP-depleted cells, was pH-dependent to the same extent as transport of the non-metabolizable sugars. 3. Glucose consumption rates were about 8-fold higher at pH 8.5 than at pH 6.4. About 65-85% of glucose was converted into lactate. Sugar transport rates were 2.5-fold higher at pH 8.5 than at pH 6.3. 4. pH affected both simple diffusion and facilitated diffusion. pH effect was mainly on the Vmax. of 2-deoxyglucose uptake, and on the rapid-uptake phase of 3-O-methylglucose transport. 5. It was estimated that about 70% of the pH effect on the rates of glucose consumption may be due to the effect on sugar transport and the remainder to the effect on the activities of glycolytic enzymes.