title: The bactericidal agent triclosan modulates thyroid hormone-associated gene expression and disrupts postembryonic anuran development.
abstract: We investigated whether exposure to environmentally relevant concentrations of the bactericidal agent, triclosan, induces changes in the thyroid hormone-mediated process of metamorphosis of the North American bullfrog, Rana catesbeiana and alters the expression profile of thyroid hormone receptor (TR) alpha and beta, basic transcription element binding protein (BTEB) and proliferating nuclear cell antigen (PCNA) gene transcripts. Premetamorphic tadpoles were immersed in environmentally relevant concentrations of triclosan and injected with 1 x 10(-11)mol/g body weight 3,5,3'-triiodothyronine (T3) or vehicle control. Morphometric measurements and steady-state mRNA levels obtained by quantitative polymerase chain reaction were determined. mRNA abundance was also examined in Xenopus laevis XTC-2 cells treated with triclosan and/or 10nM T3. Tadpoles pretreated with triclosan concentrations as low as 0.15+/-0.03 microg/L for 4 days showed increased hindlimb development and a decrease in total body weight following T3 administration. Triclosan exposure also resulted in decreased T3-mediated TRbeta mRNA expression in the tadpole tail fin and increased levels of PCNA transcript in the brain within 48 h of T3 treatment whereas TRalpha was unaffected [corrected] Triclosan alone altered thyroid hormone receptor alpha transcript levels in the brain of premetamorphic tadpoles and induced a transient weight loss. In XTC-2 cells, exposure to T3 plus nominal concentrations of triclosan as low as 0.03 microg/L for 24h resulted in altered thyroid hormone receptor mRNA expression. Exposure to low levels of triclosan disrupts thyroid hormone-associated gene expression and can alter the rate of thyroid hormone-mediated postembryonic anuran development.
authors.affiliation: Department of Biochemistry and Microbiology, P.O. Box 3055, Stn. CSC, University of Victoria, Victoria, British Columbia V8W 3P6, Canada.
authors.forename: Nik
authors.initials: N
authors.lastname: Veldhoen
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Skirrow
authors.forename: Heather
authors.initials: H
authors.lastname: Osachoff
authors.forename: Heidi
authors.initials: H
authors.lastname: Wigmore
authors.forename: David J
authors.initials: DJ
authors.lastname: Clapson
authors.forename: Mark P
authors.initials: MP
authors.lastname: Gunderson
authors.forename: Graham
authors.initials: G
authors.lastname: Van Aggelen
authors.forename: Caren C
authors.initials: CC
authors.lastname: Helbing
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000633:toxicity*; D001835:Body Weight / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002460:Cell Line; D017931:DNA Primers / Q000737:chemistry; D015870:Gene Expression / Q000187:drug effects*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D008675:Metamorphosis, Biological / Q000187:drug effects*; D018809:Proliferating Cell Nuclear Antigen / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D011892:Rana catesbeiana / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D011988:Receptors, Thyroid Hormone / Q000096:biosynthesis / Q000187:drug effects* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D013997:Time Factors; D014260:Triclosan / Q000737:chemistry / Q000633:toxicity*; D014284:Triiodothyronine / Q000737:chemistry / Q000502:physiology; D014874:Water Pollutants, Chemical / Q000633:toxicity; D014982:Xenopus laevis
chemical_list: D000900:Anti-Bacterial Agents; D017931:DNA Primers; D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger; D011988:Receptors, Thyroid Hormone; D014874:Water Pollutants, Chemical; D014284:Triiodothyronine; D014260:Triclosan