Hydroxylated polychlorinated biphenyls (OH-PCBs) induce vitellogenin through estrogenic activity in primary-cultured hepatocytes of the Xenopus laevis.

Vitellogenin (VTG)-inducing activities of 21 kinds of hydroxylated polychlorinated biphenyls (OH-PCBs) were investigated by an assay system using the primary-cultured hepatocyte of the adult male Xenopus laevis. An enzyme-linked immunoabsorbent assay (ELISA) was able to detect VTG at a minimum detection limit of 0.2ngmL(-1). The levels of VTG production in hepatocytes of male X. laevis exposed to six kinds of OH-PCB isomers (2'-OH-CB30, 3'-OH-CB30, 4'-OH-CB30, 4'-OH-CB50, 4'-OH-CB61 4'-OH-CB65) were significantly higher as compared to the control group (p<0.05). The relative ranking of the OH-PCBs was E2 (100%), 4'-OH-CB30 (2.0%)>2'-OH-CB30 (0.15%)>4'-OH-CB61 (0.046%)>3'-OH-CB30 (0.013%)>4'-OH-CB50 (0.002%)>4'-OH-CB65 (0.0001%). Although there were some differences between the estrogenicity values by the VTG-inducing activities and yeast two-hybrid assay for human estrogen receptor alpha (ERalpha). The results from VTG-assays suggested that an important factor for determining estrogenicity is the positions of the hydroxyl group and chlorine with the highest activity resulting from a para-hydroxyl group. The OH-PCB structures of high rank order in the VTG-assay had no chlorine substituted phenolic ring. Moreover, the meta-chlorine substituted phenolic ring is an important factor in determining estrogenicity. The OH-PCBs with meta-chlorine substituted phenolic ring did not show estrogenicity during VTG-assay.