Glucose-metabolizing Enzymes of the Mouse Erythrocyte: Activity Changes During Stress Erythropoiesis

Many features of normal and abnormal erythropoiesis have been described in the inbred mouse, but no systematic studies of enzymatic activities in mouse erythrocytes have been reported. The activities of 14 enzymes of glycolysis and the hexose monophosphate shunt have been measured in mouse erythrocytes formed under normal conditions and during hemopoietic stress induced by phenylhydrazine treatment. The responses of inbred strains A/J and C57L/J were compared. In normal cells of each strain the activity of hexokinase was lowest, that of triosephosphate isomerase the highest, and the rank order of other enzymatic activities in the mouse was similar to that reported for the human erythrocyte. All enzymatic activities increased during the reticulocytosis accompanying stress erythropoiesis, with phosphofructokinase, aldolase, phosphoglycerate mutase, and glucose 6-phosphate dehydrogenase (G6-PD) showing the greatest relative elevations. Enzymatic activities declined rapidly during the 2-wk period following the initial reticulocytosis, suggesting that large numbers of immature erythrocytes with high enzymatic activities and shortened life spans had been produced during the response to erythropoietic stress. In normal hemolysates heated at 50°C, the most labile enzymes were glucose 6-phosphate dehydrogenase, enolase, and glyceraldehyde phosphate dehydrogenase. In the presence of erythrocyte stromata, glucose 6-phosphate dehydrogenase was more thermolabile in hemolysates of strain C57L/J than in those of A/J. This difference correlates both with the markedly lower activity of G6-PD in normal erythrocytes of C57L/J mice compared to erythrocytes of A/J mice and with the more rapid decrease in G6-PD dehydrogenase activity in aging erythrocytes of C57L/J.