In vitro hepatic metabolism of polychlorinated biphenyls with different chlorine-substituted structures in rats and humans: Kinetics, metabolism, and potential nuclear receptor affinities.

In this study, the biotransformation behavior and potential nuclear receptor affinities of polychlorinated biphenyls (PCBs) with different chlorine-substituted structures (PCB 77/110/136/174) were explored using human and rat liver microsomes (HLM and RLM). The rate constants (kobs) of PCBs showed the variations in the order patterns for the HLM (PCB 136 > PCB 110 > PCB 174 > PCB 77) and RLM (PCB 110 > PCB 136 > PCB 174 > PCB 77). However, studied PCBs showed similar metabolite profiles and enantioselective of PCBs between HLM and RLM. The Mono-OH-PCBs were the major metabolites of PCB 77/174, whereas mono-OH- and di-OH-PCBs were the major metabolites of PCB 110/136 for the HLM and RLM, indicating that OH-PCBs could be further oxidized. Enantiomeric enrichment of (-)-PCB 136 and (+)-PCB 174 was observed in microsomal metabolism. Moreover, the inflection point of the enantiomer fraction for PCB 136 metabolized by the HLM suggests a competitive metabolism between individual atropisomers. Furthermore, molecular docking results demonstrated the relatively high affinity between PCBs (or OH-PCBs) and certain nuclear receptors, indicating that abnormal metabolic enzyme expression and endocrine disruption occur in PCB-exposed humans.