title: Triclosan exposure alters postembryonic development in a Pacific tree frog (Pseudacris regilla) Amphibian Metamorphosis Assay (TREEMA).
abstract: The Amphibian Metamorphosis Assay (AMA), developed for Xenopus laevis, is designed to identify chemicals that disrupt thyroid hormone (TH)-mediated biological processes. We adapted the AMA for use on an ecologically-relevant North American species, the Pacific tree frog (Pseudacris regilla), and applied molecular endpoints to evaluate the effects of the antibacterial agent, triclosan (TCS). Premetamorphic (Gosner stage 26-28) tadpoles were immersed for 21 days in solvent control, 1.5 μg/L thyroxine (T(4)), 0.3, 3 and 30 μg/L (nominal) TCS, or combined T(4)/TCS treatments. Exposure effects were scored by morphometric (developmental stage, wet weight, and body, snout-vent and hindlimb lengths) and molecular (mRNA abundance using quantitative real time polymerase chain reaction) criteria. T(4) treatment alone accelerated development concomitant with altered levels of TH receptors α and β, proliferating cell nuclear antigen, and gelatinase B mRNAs in the brain and tail. We observed TCS-induced perturbations in all of the molecular and morphological endpoints indicating that TCS exposure disrupts coordination of postembryonic tadpole development. Clear alterations in molecular endpoints were evident at day 2 whereas the earliest morphological effects appeared at day 4 and were most evident at day 21. Although TCS alone (3 and 30 μg/L) was protective against tadpole mortality, this protection was lost in the presence of T(4). The Pacific tree frog is the most sensitive species examined to date displaying disruption of TH-mediated development by a common antimicrobial agent.
authors.affiliation: Nautilus Environmental, Burnaby, BC, Canada.
authors.forename: Vicki L
authors.initials: VL
authors.lastname: Marlatt
authors.forename: Nik
authors.initials: N
authors.lastname: Veldhoen
authors.forename: Bonnie P
authors.initials: BP
authors.lastname: Lo
authors.forename: Dannika
authors.initials: D
authors.lastname: Bakker
authors.forename: Vicki
authors.initials: V
authors.lastname: Rehaume
authors.forename: Kurtis
authors.initials: K
authors.lastname: Vallée
authors.forename: Maxine
authors.initials: M
authors.lastname: Haberl
authors.forename: Dayue
authors.initials: D
authors.lastname: Shang
authors.forename: Graham C
authors.initials: GC
authors.lastname: van Aggelen
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Skirrow
authors.forename: James R
authors.initials: JR
authors.lastname: Elphick
authors.forename: Caren C
authors.initials: CC
authors.lastname: Helbing
mesh_terms: D000818:Animals; D001001:Anura / Q000502:physiology*; D001822:Body Burden; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D007814:Larva / Q000737:chemistry / Q000187:drug effects; D008675:Metamorphosis, Biological / Q000187:drug effects*; D016019:Survival Analysis; D014260:Triclosan / Q000032:analysis / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D014260:Triclosan