The kinetics of drug-membrane interactions in human erythrocytes from neonates.

The kinetics of drug-membrane interactions of erythrocytes from neonates were compared with those from adults by monitoring the time course of the shape transformations and vesicle release caused by drugs, using a light microscope--video recording technique. Both crenation caused by lysophosphatidylcholine (LPC) and cupping caused by chlorpromazine (CPZ) took place more slowly in the neonatal cells than in the cells from adults. The equilibrium concentrations of LPC and CPZ in erythrocytes did not differ significantly between the neonates and adults, however. The slower responses of the neonatal erythrocytes can be explained by the presence of negatively charged phosphatidylethanolamine and phosphatidylserine in the outer layer of the erythrocyte membrane, which may reduce the rate of incorporation of amphipathic LPC and attract cationic CPZ to remain in the outer membrane layer, lowering the rate of inward bending of the membrane normally caused by CPZ.