Effects of receptor-specific antibody on the uptake of desialylated glycoproteins in the isolated perfused rat liver

Removal of the terminal sialic acid residues from most mammalian glycoproteins results in their rapid transfer from the circulation into the liver. In vitro, these desialylated glycoproteins bind to a specific membrane-associated hepatic lectin which has a ubiquitous distribution within the liver cell. In the present study, infusion of a specific antibody to the purified lectin into the portal vein of an isolated perfused rat liver prior to injection of radiolabeled asialoorosomucoid or bilirubin reduced the rate of influx of asialoorosomucoid into the liver by over 80%, while the influx of bilirubin was unchanged. Although uptake of asialoorosomucoid remained blocked for at least 90 min after excess antibody was removed from the perfusion system, the total hepatic content of functional binding protein was nearly normal. These results indicate that interaction with specific cell surface lectin is essential for removal of asialoorosomucoid from the circulation. During the 90 min following infusion of antibody, no functional lectin is restored to the surface of hepatocytes.