Albumin binding sites of human hepatocytes

Recent studies of hepatitis B virus suggest that polymeric human serum albumin may facilitate the attachment of the virus via albumin receptors to hepatocytes during the infectious process. If this hypothesis is correct, hepatocytes should express binding sites for polymeric albumin. We employed the red blood cell adherence test using albumin-coated red blood cells as indicator cells on frozen sections of normal human livers to demonstrate these binding sites. Hepatocytes showed binding activity for both polymeric and monomeric albumin from different species. The receptor-ligand interaction was temperature and pH dependent, Ca++ independent and not altered by mercaptoethanol treatment. The binding activity was sensitive to neuraminidase and pronase, but resistant to trypsin, lipase and collagenase digestion. These findings suggest that human hepatocytes display species-non-specific albumin binding sites, which are glycoproteins.