Applications of the in vitro aryl hydrocarbon hydroxylase induction assay for determining "2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents": pyrolyzed brominated flame retardants.
The pyrolysis of brominated flame retardants FR 300 BA (decabromobiphenyl) ether, FireMaster BP-6 (polybrominated biphenyls), Bromkal 70-5-DE (primarily pentabromodiphenylether), Bromkal 70-DE (primarily penta and tetrabromodiphenylether) and Bromkal G1 (pentabromodiphenylether) resulted in the formation of relatively high levels of polybrominated dibenzofurans (PBDFs) and dibenzo-p-dioxins (PBDDs as determined by gas chromatography-mass spectrometric analysis. The dose response EC50 values for the induction of aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) by the flame retardant pyrolysates was determined in rat hepatoma H-4-II E cells and compared to the relative induction activities of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the concentrations of "2,3,7,8-TCDD equivalents" were calculated. The range of "2,3,7,8-TCDD equivalents" levels (micrograms/g or ppm) derived from values obtained from the AHH and EROD bioassays for each of the pyrolyzed flame retardant samples was: 174-194, 480-1400, 2140-4680, 6740-8780 and 3920-5260 ppm for FR 300 BA, FireMaster BP-6, Bromkal 70 DE, Bromkal 70-5 DE and Bromkal G1, respectively. The in vivo dose-response effects of 2 pyrolyzed flame retardants were determined in immature male Wistar rats and compared to the dose-response activities of 2,3,7,8-TCDD. The in vivo responses which were measured included hepatic microsomal AHH and EROD induction, body weight loss and thymic atrophy. For the pyrolyzed FireMaster BP-6 and Bromkal 70-5 DE samples, the range of calculated in vivo "2,3,7,8-TCDD equivalents" (ppm in sample) for the 4 in vivo bioassays was 520-1780 ppm and 3860-8960 ppm, respectively. The excellent overlap between the in vivo and in vitro 2,3,7,8-TCDD equivalents for the 2 flame retardant pyrolysate extracts supports the utility of the in vitro induction bioassay for quantitatively determining "2,3,7,8-TCDD equivalents" for mixtures containing toxic halogenated aryl hydrocarbons.
Zacharewski
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Department of Physiology and Pharmacology, College of Veterinary Medicine, Texas A and M University, College Station 77843.
Harris
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Safe
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Thoma
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Hutzinger
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D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis*; D001572:Benzofurans / Q000633:toxicity; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis; D004147:Dioxins / Q000633:toxicity; D004790:Enzyme Induction / Q000187:drug effects; D005411:Flame Retardants / Q000633:toxicity*; D008401:Gas Chromatography-Mass Spectrometry; D006358:Hot Temperature; D006842:Hydrocarbons, Brominated / Q000633:toxicity*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D010088:Oxidoreductases / Q000096:biosynthesis; D011075:Polybrominated Biphenyls / Q000633:toxicity; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D051381:Rats; D011919:Rats, Inbred Strains
D001572:Benzofurans; D004147:Dioxins; D005411:Flame Retardants; D006842:Hydrocarbons, Brominated; D011075:Polybrominated Biphenyls; D000072317:Polychlorinated Dibenzodioxins; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1