Erythrocyte metabolism. III. Relationship of energy metabolism and serum factors to the osmotic fragility following incubation

Abstract

Abstract Incubation of fresh human blood at 37 ° C. results in a progressive increase in the osmotic fragility of the erythrocytes. This increase in erythrocyte osmotic fragility following incubation at 37 ° C. in serum is related to changes that occur in the serum and to conditions affecting glucose metabolism of erythrocytes. In this study normal human erythrocytes showed no change in osmotic fragility when incubated for 24 hours at 37 ° C., pH 7.5, and hematocrit level 10 per cent in serum previously heated at 56 ° C. for 30 minutes. The heat-labile property of serum that is partially responsible for the increase in the osmotic fragility of erythrocytes is the process of esterification of the free cholesterol in serum which results in a decrease in the free cholesterol in serum and a corresponding increase in the cholesterol esters. When cells are incubated in native serum in which the concentration of free cholesterol is decreased, there is a loss of erythrocyte cholesterol to the serum. This loss of erythrocyte cholesterol correlates directly with an increase in erythrocyte osmotic fragility. Adequate production and utilization of energy derived from glucose metabolism are also necessary during incubation to prevent an increase in the osmotic fragility of erythrocytes. Incubation of erythrocytes in heated serum at pH 7.0 results in a 50 per cent inhibition of glycolysis compared with pH 7.5. Erythrocytes show an increase in osmotic fragility and changes in cation concentration after 24 hour incubation at pH 7.0 or in glucose-free serum at pH 7.5. Incubation of erythrocytes in the presence of ouabain at pH 7.5 results in an increase in osmotic fragility and an increase in cation concentration of erythrocytes. The increase in osmotic fragility associated with inhibition of glucose metabolism or following incubation with ouabain occurs without change in erythrocyte cholesterol. Thus the maintenance of the osmotic fragility of erythrocytes during incubation in serum is dependent on adequate energy production from glucose metabolism and the prevention of a decrease in the free cholesterol of serum.