In vitro dioxin-like potencies of HO- and MeO-PBDEs and inter-species sensitivity variation in birds.

Due to their bioaccumulative properties, hydroxylated and methoxylated polybrominated diphenyl ethers (HO-/MeO-PBDEs) may pose ecological risks to wild life, including birds. However, their toxicity potencies in avian species are largely unknown. In the present study, an avian AHR1 luciferase reporter gene (LRG) assay with luciferase probes from chicken, pheasant and quail was used to test activations of avian aryl hydrocarbon receptor (AHR)-mediated pathways by 19 HO- or MeO-PBDEs in different avian species. Species-specific relative potencies (RePs) of HO-/MeO-PBDEs to tetrachlorodibenzo-p-dioxin (TCDD) and relative sensitivities of various species to each chemical were estimated. The results indicated that the ReP of the most potent HO-/MeO-PBDEs, 5-Cl-6-HO-BDE-47, was 7.8×10(-4) for chicken, 1.1×10(-2) for pheasant, and 1.7×10(-1) for quail comparing to TCDD. In addition, it was found that avian species with the greatest sensitivity to TCDD did not always have the greatest sensitivity to HO-/MeO-PBDEs and vice versa. This study contributed to filling in the knowledge gap regarding the dioxin-like activity of HO-/MeO-PBDEs in birds, and provided beneficial information for the prioritization of HO-/MeO-PBDEs for further research. CAPSULE ABSTRACT: HO-/MeO-PBDEs activate avian AHR-mediated pathways in a congener- and species- specific manner. 5-Cl-6-HO-BDE-47 was the most potent among the nineteen HO-/MeO-PBDEs tested.