title: 1,2-Dibromo-4-(1,2-dibromoethyl)-cyclohexane and tris(methylphenyl) phosphate cause significant effects on development, mRNA expression, and circulating bile acid concentrations in chicken embryos.
abstract: 1,2-Dibromo-4-(1,2-dibromoethyl)-cyclohexane (DBE-DBCH; formerly abbreviated as TBECH) and tris(methylphenyl) phosphate (TMPP; formerly abbreviated as TCP) are additive flame retardants that are detected in the environment and biota. A recent avian in vitro screening study of 16 flame retardants identified DBE-DBCH and TMPP as important chemicals for follow-up in ovo evaluation based on their effects on cytotoxicity and mRNA expression in avian hepatocytes. In this study, technical mixtures of DBE-DBCH and TMPP were injected into the air cell of chicken embryos at concentrations ranging from 0 to 54,900ng/g and from 0 to 261,400ng/g, respectively, to determine effects on pipping success, development, hepatic mRNA expression, thyroid hormone levels, and circulating bile acid concentrations. Both compounds were detectable in embryos at pipping and the β-DBE-DBCH isomer was depleted more rapidly than the α-isomer in tissue samples. DBE-DBCH had limited effects on the endpoints measured, with the exception of the up-regulation of two phase I metabolizing enzymes, CYP3A37 and CYP2H1. TMPP exposure caused embryonic deformities, altered growth, increased liver somatic index (LSI) and plasma bile acid concentrations, and altered mRNA expression levels of genes associated with xenobiotic and lipid metabolism and the thyroid hormone pathway. Overall, TMPP elicited more adverse molecular and phenotypic effects than DBE-DBCH albeit at concentrations several orders of magnitude greater than those detected in the environment. The increase in plasma bile acid concentrations was a useful phenotypic anchor as it was associated with a concomitant increase in LSI, discoloration of the liver tissue, and modulation of hepatic genes involved with xenobiotic and lipid metabolism.
authors.affiliation: National Wildlife Research Centre, Environment Canada, Ottawa, ON K1A 0H3, Canada. Electronic address: doug.crump@ec.gc.ca.
authors.forename: Doug
authors.initials: D
authors.lastname: Crump
authors.affiliation: National Wildlife Research Centre, Environment Canada, Ottawa, ON K1A 0H3, Canada.
authors.forename: Emily
authors.initials: E
authors.lastname: Porter
authors.affiliation: National Wildlife Research Centre, Environment Canada, Ottawa, ON K1A 0H3, Canada.
authors.forename: Caroline
authors.initials: C
authors.lastname: Egloff
authors.affiliation: National Wildlife Research Centre, Environment Canada, Ottawa, ON K1A 0H3, Canada.
authors.forename: Kim L
authors.initials: KL
authors.lastname: Williams
authors.affiliation: National Wildlife Research Centre, Environment Canada, Ottawa, ON K1A 0H3, Canada.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Letcher
authors.affiliation: National Wildlife Research Centre, Environment Canada, Ottawa, ON K1A 0H3, Canada.
authors.forename: Lewis T
authors.initials: LT
authors.lastname: Gauthier
authors.affiliation: National Wildlife Research Centre, Environment Canada, Ottawa, ON K1A 0H3, Canada; Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
authors.forename: Sean W
authors.initials: SW
authors.lastname: Kennedy
mesh_terms: D000818:Animals; D001647:Bile Acids and Salts / Q000097:blood* / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000633:toxicity*; D002642:Chick Embryo; D003510:Cyclohexanes / Q000633:toxicity*; D004785:Environmental Pollutants / Q000633:toxicity; D005411:Flame Retardants / Q000633:toxicity*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D008099:Liver / Q000378:metabolism; D015394:Molecular Structure; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013974:Thyroxine / Q000097:blood
chemical_list: D001647:Bile Acids and Salts; D019086:Bridged Bicyclo Compounds, Heterocyclic; D003510:Cyclohexanes; D004785:Environmental Pollutants; D005411:Flame Retardants; D012333:RNA, Messenger; C065518:4-ethyl-1-phospha-2,6,7 trioxabicyclo(2.2.2)octane-1-oxide; C517232:1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane; D013974:Thyroxine
keywords: 1,2-Dibromo-4-(1,2-dibromoethyl)-cyclohexane; Bile acids; Chicken; Embryonic development; Tris(methylphenyl) phosphate; mRNA expression