Effect of dimyristoyl phosphatidylcholine on intact erythrocytes. Release of spectrin-free vesicles without ATP depletion.

Incubation of human erythrocytes with suspensions of sonicated dimyristoyl phosphatidylcholine resulted in dramatic morphological changes of the cells and release of membrane vesicles. The shedding of membrane vesicles was not preceded by ATP depletion and only occurred at temperatures of incubation that were above the phase transition temperature of dimyristoyl phosphatidylcholine. Membrane vesicles were separated from intact erythrocytes and exogenous dimyristoyl phosphatidylcholine by a series of centrifugation steps. The lipid composition of the membrane vesicles was similar to that of the native erythrocyte, and the predominant membrane proteins were band 3, glycophorin and acetylcholinesterase. Spectrin was not detected. Freeze-fracture electron microscopy showed vesicles (150 nm in diameter) with protein particles embedded in the lipid bilayer.