Comparative In Vitro and In Vivo Hydroxylation Metabolization of Polychlorinated Biphenyl 101 in Laying Hens: A Pilot...

Polychlorinated biphenyls (PCBs) can be metabolized into hydroxylated PCBs (OH-PCBs) that exhibit greater toxicity than their parent compounds. In particular, 2,2',4,5,5'-pentachlorobiphenyl (PCB 101) is commonly found in chicken feeds and breeding environments, although information on the biotransformation of this PCB in chickens is lacking. In this study, the hydroxylation metabolization of PCB 101 was assessed based on in vitro trials with Sanhuang chicken liver microsomes and in vivo experiments with Hy-Line Brown hens. The para-substituted metabolite 4'-OH-PCB 101 is the predominant metabolite of PCB 101. 4'-OH-PCB 101 is preferentially retained in the chicken bloodstream and partly distributed into different tissues of laying hens. The blood-brain barrier can effectively prevent the OH-PCB from entering the brain, and the adipose tissue contains a relatively low residue concentration of the OH-PCB. The laying hen can deplete the OH-PCB via laying eggs and excrement. The ratio of 4'-OH-PCB 101/PCB 101 in egg yolk is about 1:2. These results first provide definite evidence for the previous hypothesis of the PCB 101 metabolism by chickens. They could assist in predicting the environmental fate of PCBs, and in the risk assessment of PCBs and OH-PCBs in chicken-based foodstuffs.