Specific 125I-radioimmunoassay for cholyglycine, a bile acid, in serum

The concentration of the conjugated bile acid, cholylglycine, in serum is a sensitive and specific indicator of hepatic function. We describe a convenient, specific, and precise radioimmunoassay for cholylglycine, in which 125I-labeled cholylglycyltyrosine is used as tracer. In addition, a blocking agent in the buffer system eliminates binding of bile acids to serum albumin. Therefore no extraction is required. We found no interference by (a) abnormal concentrations of albumin or gamma-globulin, (b) lipemic sera, (c) hemolyzed sera, (d) anticoagulants, or (e) various commonly used drugs. The reference interval for fasting subjects is estimated to be 0.0 to 0.6 mg/L. Our clinical studies show that serum cholylglycine concentrations are usually abnormal in most hepatobiliary diseases, such as viral hepatitis, alcoholic liver disease, cirrhosis, and pediatric liver diseases.