Temperature-dependent vesiculation of human erythrocytes caused by hypertonic salt: A phenomenon involving lipid segregation

Treatment of human erythrocytes with 4 M NaCl causes hemolysis with concomitant release of microvesicles from the membrane. The microvesicles have an average diameter of 200–300 nm and reveal an in creased lipid content in particular of cholesterol and sphingomyelin. Phosphatidylcholine and phosphatidylserine contents remain unaltered whereas the phosphatidylethanolamine content is lowered in comparison with the erythrocyte membrane.Decreasing the temperature at which the microvesicles are produced causes an increase in the cholesterol/phospholipid ratio, the sphingomyelin/phosphatidylethanolamine ratio, and the amino-phospholipids, which contain low amounts of arachidonic acid.The total protein content of the vesicles is further decreased when the temperature is lowered. This is due to a reduced content of spectrin and several integral membrane proteins. The results indicate that a significant, temperature-dependent segregation of membrane constituents occurs during the vesiculation process.