In vitro response of fish and mammalian cells to complex mixtures of polychlorinated naphthalenes, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons.

In vitro characterization and comparison of responses to different classes of biologically active compounds can increase the utility of bioassays. In this study, the relative potencies (REPs) of mixtures of polychlorinated naphthalenes (PCNs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs), to induce in vitro ethoxyresorufin-O-deethylase (EROD) in PLHC-1 fish hepatoma cells, H4IIE wild type (H4IIE-wt) rat hepatoma cells, and recombinant H4IIE cells (H4IIE-EROD) were determined. The mixtures were also analyzed by in vitro luciferase assay with recombinant H4IIE cells (H4IIE-luc). Halowaxes 1051, 1014, and 1013 caused significant induction in all three H4IIE assays at concentrations less than 10 mg/l, but did not elicit a significant response in the PLHC-1 assay. Based on H4IIE results, the Halowaxes were estimated to have relative potencies (REPs) of approximately 10(-6)-10(-8) relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Less than 5 mg/l of Aroclors 1242, 1248, 1254; Clophens A60, T64; and Chlorofen induced significant responses in the H4IIE assays, while only Clophens A60 and T64 caused a significant response in the PLHC-1 assay. The efficacy of the Aroclor mixtures was generally insufficient to allow for quantitative REP estimates, but, based on their responses in the H4IIE assays, Clophen A60 and Chlorofen were estimated to have REPs of approximately 10(-6) and 10(-7), respectively. A mixture of 16 priority PAHs caused significant induction in all four cell types and was estimated to have a REP of approximately 10(-4). Overall, the results of this study add to a growing database on the dioxin-like potency of complex mixtures of xenobiotics, and suggested that H4IIE-based in vitro bioassays were more sensitive than PLHC-1 cells for detecting dioxin-like activity in complex mixtures.