Dynamic behaviour of amphiphilic lipids to penetrate into membrane of intact human erythrocytes and to induce change in the cell shape.

Shape change (crenation, echinocyte formation) of intact human erythrocytes induced by added phosphatidylcholine or lysophosphatidylcholine species with varying acyl chain lengths was dependent only on the amount of the lipid incorporated into the membrane (determined with 14C-labelled lipids), irrespective of the chain length. The chain length appears to determine the speed and the maximal extent of the lipid transfer from the outside medium into the membrane. The altered shape gradually reverted upon incubation at 37 degrees C, not at low temperature, until the cells reassumed their normal shape. Translocation of the incorporated lipid molecules from the outer to the inner leaflet of the membrane lipid bilayer occurred to a slight extent during the incubation.