EFFECT OF INCREASING THE INTRACELLULAR RATIO OF NADH TO NAD+ ON HUMAN-ERYTHROCYTE METABOLISM - NEW ESTIMATION OF THE TURNOVER THROUGH THE PHOSPHOGLYCERATE SHUNT

The metabolism of glucose in human erythrocytes was investigated under conditions where the ratio of NADH to NAD+ was increased. This was achieved by 3 methods: first, by adding lactate dehydrogenase together with NADH extracellularly; second, by adding xylitol; and third, by adding acetaldehyde. The concentrations of glyceraldehyde-3-phosphate, dihydroxyacetone phosphate and fructose-1,6-bisphosphate increased and the level of 1,3-diphosphoglycerate decreased drastically. The 3-phosphoglycerate concentration and Pi changed only slightly. This, together with the large decrease in the 1,3-diphosphoglycerate concentration, produced 2 other effects. The ratio of ATP to ADP decreased to a new steady state in keeping with the phosphoglycerate kinase equilibrium. 2,3-Diphosphoglycerate was broken down at a slow rate, 4-8% of the lactate production, which is interpreted as the normal rate under conditions of steady state in the circulation.