Recovery of human erythrocytes from the echinocyte shape induced by added choline-phospholipids is dependent on the acyl chain length.

Addition of an amphiphilic lipid, such as phosphatidylcholine (PC) species with two identical saturated chains or lysophosphatidylcholine (lysoPC) species with one saturated acyl chain of various lengths, into a suspension of intact human erythrocytes resulted in lipid incorporation into the erythrocytes membrane to produce echinocytes (crenated cells). The altered shape gradually reverted on incubation at 37 degrees C until the cells reassumed their normal disc shape. The rate of such recovery of shape increased with decreasing acyl chain length for both PC with C8-C12 acyl chains and lysoPC with a C14-C18 acyl chain, and was strongly influenced by incubation temperature. The identical rate of recovery of shape was observed for cells with normal, decreased or increased ATP content, implying that the metabolic state of the cell had no influence on the recovery process. Recovery of shape is therefore considered to be caused by translocation of the incorporated lipid molecules from the outer to the inner leaflet of the membrane lipid bilayer and the rate of recovery increases with decreasing hydrophobicity of the lipid.