Hereditary spherocytosis (HS) red cells lose membrane lipids excessively during incubation in vitro. Individual phosphatides as well as cholesterol are lost in proportion to their content in membranes, suggesting that fragments of membrane are removed. Supplementation of HS red cells with glucose during incubation has no consistent protective effect, whereas diminishing the excessive sodium flux through these cells by suspending them in either sodium-free or hypertonic media prevents membrane fragmentation. The characteristic excessive increase in osmotic fragility which occurs in incubated HS red cells results both from inordinate accumulation of intracellular sodium ions which produces osmotic swelling, and from depletion of surface material which generates microspherocytosis. Inhibiting both of these processes by incubating HS red cells in sodium-free media completely prevents increases in osmotic fragility despite prolonged incubation.
Harry S. Jacob