Modified radioassay for measuring asialoglycoprotein in serum.

Asialoglycoproteins are removed from the circulation by the carbohydrate-specific hepatic binding protein in the rat. Asialoglycoprotein in human serum can be detected by an inhibition assay in which the binding of 125I-labeled asialo-alpha 1-acid glycoprotein (ASAG) to purified hepatocyte membranes is inhibited by known amounts of ASAG or patient's serum. We were able to reproducibly measure inhibition equivalent to that of 1 to 20 ng of ASAG. The mean concentration of inhibitor in 11 healthy control patients was equivalent to 0.153 (SD = 0.051) mg of ASAG per liter, measured in 20 microL of serum. Significant increases of inhibitor were observed in patients with malignant extrahepatic biliary obstruction, alcoholic liver disease, viral hepatitis, or liver metastases, but not in those with benign biliary obstruction. For a set of six control sera the intra- and interassay CVs were 9.1% and 25.2%, respectively (n = 3 each).