On the mechanism of polychlorinated biphenyl-induced hypobilirubinaemia.

Treatment of normal rats with a polychlorinated biphenyl mixture of DDT increased liver microsomal protein concentration. Hepatic microsomal bilirubin UDP-glucuronyltransferase activity was elevated in the DDT-treated, but not in the polychlorinated biphenyl-treated rats. In contrast polychlorinated biphenyl, but not DDT, reduced serum bilirubin concentrations in jaundiced Gunn rats, as did sulphadiazine; sulphonamides compete with bilirubin for binding sites on plasma albumin. Polychlorinated biphenyls appear to lower serum bilirubin concentration by reducing the binding of bilirubin to plasma protein.