title: Biotransformation enzymes and thyroid axis disruption in juvenile rainbow trout (Oncorhynchus mykiss) exposed to hexabromocyclododecane diastereoisomers.
abstract: Juvenile rainbow trout (Oncorhynchus mykiss) were fed either a reference diet or one of three diets enriched with alpha, beta, or gamma diastereoisomers of hexabromocyclododecane (HBCD, C12H18Br6) for 56 days. This exposure period was followed by 112 days during which all fish were fed the reference diet. Potential effects of HBCD on phase I and II biotransformation enzyme activities and thyroid axis disruption were examined. Disruption of the thyroid axis was most evident in the gamma-HBCD exposed group, as indicated by lower circular FT4 and higher FT3 as well as an increase in thyroid epithelial cell height. However, fish fed the alpha-HBCD enriched diet also exhibited altered glucuronyltransferase activity and thyroid epithelial cell heights and the beta-HBCD group had altered FT4 and FT3 and glucuronyltransferase activity. T4ORD activity was not affected after 14 days, but was significantly lower among all HBCD exposed fish compared to the reference fish after 56 days. Results from these experiments indicate that all isomers have the potential to disrupt thyroid homeostasis.
authors.affiliation: Department of Fisheries & Ocean, Freshwater Institute, Winnipeg, Manitoba, R3T 2N6, Canada. vince.palace@dfo-mpo.gc.ca
authors.forename: Vince P
authors.initials: VP
authors.lastname: Palace
authors.forename: Kerri
authors.initials: K
authors.lastname: Pleskach
authors.forename: Thor
authors.initials: T
authors.lastname: Halldorson
authors.forename: Robert
authors.initials: R
authors.lastname: Danell
authors.forename: Kerry
authors.initials: K
authors.lastname: Wautier
authors.forename: Bob
authors.initials: B
authors.lastname: Evans
authors.forename: Mehran
authors.initials: M
authors.lastname: Alaee
authors.forename: Chris
authors.initials: C
authors.lastname: Marvin
authors.forename: Gregg T
authors.initials: GT
authors.lastname: Tomy
mesh_terms: D000818:Animals; D001711:Biotransformation; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000473:pathology; D006842:Hydrocarbons, Brominated / Q000633:toxicity*; D007453:Iodide Peroxidase / Q000378:metabolism; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D017686:Oncorhynchus mykiss; D013237:Stereoisomerism; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D006842:Hydrocarbons, Brominated; D014874:Water Pollutants, Chemical; D014284:Triiodothyronine; C089796:hexabromocyclododecane; D007453:Iodide Peroxidase; D019363:Cytochrome P-450 CYP1A1; D013974:Thyroxine