Role of lipids in stabilizing red cells in rats.

The causes of osmotic fragility of red cells were studied in rats. Osmotic fragility of red cells in vivo changed after removal of the spleen or induction of experimental splenomegaly by repeated intraperitoneal injections of methyl cellulose (MC): in splenectomized rats, the red cells showed reduced osmotic fragility and an increase in diameter as well as in contents of phospholipids and cholesterol. Conversely in rats with splenomegaly, the cells showed increased osmotic fragility and a decrease in diameter and in lipid contents. Results confirmed that increase in the phospholipid content resulted in decreased fragility and that increase in the cholesterol content brought about decreased spherocytosis. The activity of lecithin cholesterol acyltransferase (LCAT) in the plasma varied inversely with the cholesterol content of the red cells. The above results show that the fragility of red cells is influenced by their lipid content and shape, and that LCAT activity in the plasma influences the membrane content of cholesterol and spherocytosis.