Alterations of erythrocyte morphology and lipid composition by hyperbilirubinemia.

Morphology and membrane lipid composition of erythrocytes from neonates (jaundiced and healthy) and adults (before and after incubation with bilirubin) were studied. The morphological index, expressing the relative proportions of the different stages of cell distortion, and the membrane cholesterol, phospholipids and cholesterol/phospholipids molar ratio, were determined. In jaundiced neonates a significant increase in the morphological index (P < 0.01) was found. After incubation with bilirubin, adult erythrocytes also showed an increase in the morphological index (P < 0.01). Hemolysis occurred under these conditions, and the red cell ghosts obtained (vesicles) showed a rounded morphology. Higher cholesterol/phospholipid ratio and lower phospholipid content were found in jaundiced neonates compared with healthy babies (P < 0.05) and adults (P < 0.01), as well as in the cells (P < 0.05) and vesicles (P < 0.01) obtained after bilirubin incubation. Bilirubin cytotoxicity may occur in a stepwise manner: deposition of bilirubin in membrane produces echinocytosis, which is followed by disintegration of the lipid bilayer with loss of phospholipids from the membrane.