Metabolic dependence of the critical hemolytic volume of human erythrocytes: relationship to osmotic fragility and autohemolysis in hereditary spherocytosis and normal red cells.

Erythrocytes from patients with hereditary spherocytosis (HS) undergo changes in cation and lipid content when incubated in vitro under sterile conditions for 24 hours. These are accompanied by changes in cell volume, osmotic fragility, and the critical volume at which hemoly-sis of the cell occurs. Normal red cells have been found to undergo similar changes but with a longer time scale, the normal taking 36 to 48 hours to achieve the degree of change found in the sphero-cyte at 24 hours. The osmotic fragility of the erythrocyte depends on the relationship of the osmotically active intra-cellular contents of the cell, which determine the cell volume, to the area of the nondistensible membrane. Consequently, the shape of the cell has appeared important to many authors (1-4), since the relative thickness of the cell depends on the ratio of the volume to the available surface area of the membrane. A further phenomenon that is characteristic of the HS cell is that of marked autohemolysis on in vitro incubation (5-7). The mechanism is poorly understood, although it clearly bears a re