Induction of bilirubin UDP-glucuronyltransferase and CYP4A1 P450 by co-planar PCBs: Different responsiveness of guinea pigs and rats

Induction of hepatic microsomal bilirubin UDP_glucuronyltransferase and CYP4A1 P450 by 3,4,3′,4′-tetrachlorobiphenyl (TCB) and 3,4,5,3′,4′-pentachlorobiphenyl (PenCB) was studied in guinea pigs and rats. Both enzyme activities in guinea pigs were increased 4-fold or more over the control by PenCB treatment, while by treatment with a less toxic congener, TCB, these were increased to a lesser extent. On the contrary, the rat enzymes were significantly decreased by treatment with these co-planar polychlorinated biphenyls. These results suggest that the alterations of both bilirubin UDP-glucuronyltransferase and CYP4A P450 are the characteristic indices for the toxicites of polychlorinated hydrocarbons.