title: Toxicological assessment of polychlorinated biphenyls and their metabolites in the liver of Baikal seal (Pusa sibirica).
abstract: We have previously reported that high accumulation of dioxins and related compounds induced cytochrome P450 (CYP 1s) isozymes in the liver of wild Baikal seals, implying the enhanced hydroxylation of polychlorinated biphenyls (PCBs). The present study attempted to elucidate the residue concentrations and patterns of PCBs and hydroxylated PCBs (OH-PCBs) in the livers of Baikal seals. The hepatic residue concentrations were used to assess the potential effects of PCBs and OH-PCBs in combination with the analyses of serum thyroid hormones, hepatic mRNA levels, and biochemical markers. The hepatic expression levels of CYP1 genes were positively correlated with the concentration of each OH-PCB congener. This suggests chronic induction of these CYP1 isozymes by exposure to PCBs and hydroxylation of PCBs induced by CYP 1s. Hepatic mRNA expression monitoring using a custom microarray showed that chronic exposure to PCBs and their metabolites alters the gene expression levels related to oxidative stress, iron ion homeostasis, and inflammatory responses. In addition, the concentrations of OH-PCBs were negatively correlated with L-thyroxine (T4) levels and the ratios of 3,3',5-triiodo-L-thyronine (T3)/reverse 3,3',5'-triiodo-L-thyroninee (rT3). These observations imply that Baikal seals contaminated with high levels of OH-PCBs may undergo the disruption of mechanisms related to the formation (or metabolism) of T3 and T4 in the liver.
authors.affiliation: Center for Marine Environmental Studies (CMES), Ehime University , Bunkyo-cho 2-5, Matsuyama, Ehime 790-8577, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Nomiyama
authors.forename: Shusaku
authors.initials: S
authors.lastname: Hirakawa
authors.forename: Akifumi
authors.initials: A
authors.lastname: Eguchi
authors.forename: Chika
authors.initials: C
authors.lastname: Kanbara
authors.forename: Daisuke
authors.initials: D
authors.lastname: Imaeda
authors.forename: Jean
authors.initials: J
authors.lastname: Yoo
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kunisue
authors.forename: Eun-Young
authors.initials: EY
authors.lastname: Kim
authors.forename: Hisato
authors.initials: H
authors.lastname: Iwata
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Tanabe
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004147:Dioxins / Q000378:metabolism; D004785:Environmental Pollutants / Q000633:toxicity*; D015870:Gene Expression; D006900:Hydroxylation; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D012333:RNA, Messenger / Q000378:metabolism; D046048:Seals, Earless; D013963:Thyroid Hormones / Q000097:blood; D013974:Thyroxine / Q000378:metabolism
chemical_list: D004147:Dioxins; D004785:Environmental Pollutants; D012333:RNA, Messenger; D013963:Thyroid Hormones; D003577:Cytochrome P-450 Enzyme System; D011078:Polychlorinated Biphenyls; D013974:Thyroxine