title: Derivation of 2,3,7,8-TCDD toxic equivalent factors (TEFs) for selected dioxins, furans and PCBs with rainbow trout and rat liver cell lines and the influence of exposure time.
abstract: The effect of exposure time on the induction of 7-ethoxyresorufin O-deethylase (EROD) by 2,3,7,8,-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and 3,3',4, 4'-tetrachlorobiphenyl (PCB 77) was examined in two liver cell lines: rainbow trout RTL-W1 and rat H4IIE. In RTL-W1, exposure time had no effect on induction EC50s and derivation of TCDD- toxic equivalency factors (TEFs). In H4IIE, EC50s for TCDD also were unchanged. However, for TCDF and PCB 77 in H4IIE, EC50s increased and TEFs decreased as exposure time increased from 6 to 72 h. These results suggest that metabolism of TCDF and PCB 77 can account for some of the previously observed differences between RTL-W1 and H4IIE TEFs.
authors.affiliation: Department of Biology, University of Waterloo, ON, Canada.
authors.forename: J H
authors.initials: JH
authors.lastname: Clemons
authors.forename: D G
authors.initials: DG
authors.lastname: Dixon
authors.forename: N C
authors.initials: NC
authors.lastname: Bols
mesh_terms: D000818:Animals; D001572:Benzofurans / Q000633:toxicity*; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis; D004790:Enzyme Induction; D008099:Liver / Q000187:drug effects*; D017686:Oncorhynchus mykiss; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D051381:Rats; D013997:Time Factors; D018675:Toxicity Tests
chemical_list: D001572:Benzofurans; D000072317:Polychlorinated Dibenzodioxins; D011078:Polychlorinated Biphenyls; D019363:Cytochrome P-450 CYP1A1; C014211:2,3,7,8-tetrachlorodibenzofuran