Role of membrane lipid distribution in chlorpromazine-induced shape change of human erythrocytes

This is a study of the morphology and transbilayer lipid distribution of human erythrocytes treated with chlorpromazine (CPZ) over extended time courses. At 0 degrees C, treatment of dilauroylphosphatidyl[1-C-14]choline-labeled erythrocytes with 120 mu M CPZ produced an immediate stomatocytic transformation (t(1/2) < 5 min) with no concurrent change in transbilayer distribution of radiolabeled lipid, as determined by bovine serum albumin extractability. At 37 degrees C, CPZ treatment of cells produced two sequential morphological effects: immediate stomatocytosis (t(1/2) < 1 min) with no concurrent change in radiolabel transbilayer distribution, followed by gradual increase in stomatocytic extent over several hours, with concurrent redistribution of radiolabeled lipid to the inner monolayer. Cells pretreated with vanadate at 37 degrees C exhibited a triphasic morphological response: CPZ produced immediate stomatocytosis, followed by a transient reversion to echinocytes lasting about 2 h, before returning to stomatocytic morphologies over the next several hours. The echinocytic reversion was accompanied by exposure of phosphatidylserine on the cell surface, as indicated by increased activation of exogenous prothrombinase. These findings suggest that while CPZ induces transbilayer lipid redistribution over extended time periods (which may mediate the complex morphological transformations observed), the early stomatocytic response elicited by addition of CPZ is not due to lipid reorganization.