Interaction of bilirubin with human erythrocyte membranes. Bilirubin binding to neuraminidase- and phospholipase-treated membranes.
Saturable bilirubin binding to human erythrocyte membranes was measured before and after digestion with neuraminidase and phospholipases. Neuraminidase-treated erythrocyte membranes did not show any change in their binding properties, indicating that gangliosides could be excluded as candidates for saturable bilirubin-binding sites on erythrocyte membranes. Although bilirubin-binding properties of the membranes did not change after phospholipase D digestion, either, phospholipase C treatment greatly enhanced bilirubin binding. Thus it is suggested that a negatively charged phosphoric acid moiety of phospholipids on the membrane surface may play a role to prevent a large amount of bilirubin from binding to the membranes. Further saturable bilirubin binding to inside-out sealed erythrocyte membrane vesicles showed values comparable with those of the right-side-out sealed membranes, suggesting that the bilirubin-binding sites may be distributed on both outer and inner surfaces of the membranes, or may exist in the membranes where bilirubin may be accessible from either side.
Department of Perinatology, Aichi Prefecture Colony, Japan.
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Sato
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Aono
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Semba
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Kashiwamata
D001663:Bilirubin / Q000097:blood*; D002794:Choline / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008055:Lipids / Q000494:pharmacology; D009439:Neuraminidase / Q000494:pharmacology; D010739:Phospholipase D / Q000494:pharmacology; D010743:Phospholipids / Q000494:pharmacology; D013053:Spectrophotometry; D010738:Type C Phospholipases / Q000494:pharmacology
D008055:Lipids; D010743:Phospholipids; D010738:Type C Phospholipases; D010739:Phospholipase D; D009439:Neuraminidase; D002794:Choline; D001663:Bilirubin