title: Revised relative potency values for PCDDs, PCDFs, and non-ortho-substituted PCBs for the optimized H4IIE-luc in vitro bioassay.
abstract: While the World Health Organization 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalency factors are useful estimates of relative potencies of mixtures when conducting risk assessments, they are not useful when comparing the results of bioassays such as the H4IIE-luc to concentrations of TCDD equivalents calculated from instrumental analyses. Since there are thousands of dioxin-like compounds (DLCs), one use of screening assays is to determine if all of the aryl hydrocarbon receptor (AhR) active DLCs in a mixture have been accounted for in instrumental analyses. For this purpose, bioassay-specific relative potency (ReP) values are needed. RePs of 21 polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls that exhibit effects mediated through the AhR were determined by use of the H4IIE-luc assay. Different values of RePs are derived, depending on the statistical, curve-fitting methods used to derive them from the dose-response relationships. Here, we discuss the various methods for deriving RePs from in vitro data and their assumptions and effects on values of RePs. Full dose-response curves of 2,3,7,8-TCDD and other representative DLCs were used to estimate effective concentrations at multiple points (e.g., EC20-50-80), which were then used to estimate ReP of each DLC to 2,3,7,8-TCDD.
authors.affiliation: NeoEnBiz Co, Daewoo Technopark, 1306, Bucheon, Republic of Korea.
authors.forename: Kyu Tae
authors.initials: KT
authors.lastname: Lee
authors.forename: Seongjin
authors.initials: S
authors.lastname: Hong
authors.forename: Jung Suk
authors.initials: JS
authors.lastname: Lee
authors.forename: Kyu Hyuck
authors.initials: KH
authors.lastname: Chung
authors.forename: Klara
authors.initials: K
authors.lastname: Hilscherová
authors.forename: John P
authors.initials: JP
authors.lastname: Giesy
authors.forename: Jong Seong
authors.initials: JS
authors.lastname: Khim
mesh_terms: D000818:Animals; D001572:Benzofurans / Q000592:standards / Q000633:toxicity*; D001681:Biological Assay / Q000379:methods / Q000592:standards*; D000072338:Dibenzofurans, Polychlorinated; D004147:Dioxins / Q000592:standards / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D006801:Humans; D011078:Polychlorinated Biphenyls / Q000592:standards / Q000633:toxicity*; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000592:standards / Q000633:toxicity; D018336:Receptors, Aryl Hydrocarbon
chemical_list: D001572:Benzofurans; D000072338:Dibenzofurans, Polychlorinated; D004147:Dioxins; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D011078:Polychlorinated Biphenyls