title: Development of metamorphosis assay using Silurana tropicalis for the detection of thyroid system-disrupting chemicals.
abstract: The West African clawed frog (Silurana tropicalis), which resembles the South African clawed frog (Xenopus laevis), but is somewhat smaller, has a diploid genome and a shorter generation time. Therefore, S. tropicalis has the potential for use as a new model in ecotoxicology. We demonstrated a S. tropicalis metamorphosis assay based on Xenopus Metamorphosis Assay (XEMA) using 1 microg/L thyroxine (T4) and 75 mg/L propylthiouracil (PTU). Tadpoles at developmental stages 48-50 were exposed to chemicals for 28 days and total body length, developmental stage, and hind limb length were recorded every 7 days. Significant differences in developmental stage and total body length were found for both T4 and PTU after 7-day exposure, which were similar to the results of the XEMA ring-test using the same chemicals. Moreover, in the present study, we measured hind limb length as a new endpoint of thyroid axis. Significant differences in the hind limb length were encountered in both T4 and PTU treatments after 7 days of exposure. These results suggest that S. tropicalis can be used in a XEMA-like protocol to detect agonist and antagonist effects of chemicals on the thyroid system. Hind limb length is also a suitable endpoint in such protocols. A new test protocol detecting both thyroid disruption and reproductive effects of chemicals using S. tropicalis should be established in the near future.
authors.affiliation: Biotechnology Research Laboratory, Towa Kagaku Co., Ltd., 3-13-26 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Mitsui
authors.forename: Takaaki
authors.initials: T
authors.lastname: Fujii
authors.forename: Maki
authors.initials: M
authors.lastname: Miyahara
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Oka
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kashiwagi
authors.forename: Keiko
authors.initials: K
authors.lastname: Kashiwagi
authors.forename: Hideki
authors.initials: H
authors.lastname: Hanada
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Urushitani
authors.forename: Noriaki
authors.initials: N
authors.lastname: Santo
authors.forename: Osamu
authors.initials: O
authors.lastname: Tooi
authors.forename: Taisen
authors.initials: T
authors.lastname: Iguchi
mesh_terms: D000818:Animals; D013956:Antithyroid Agents / Q000494:pharmacology*; D001001:Anura / Q000502:physiology; D001681:Biological Assay / Q000379:methods*; D005260:Female; D006614:Hindlimb / Q000187:drug effects / Q000254:growth & development; D006727:Hormone Antagonists / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D008297:Male; D008675:Metamorphosis, Biological / Q000187:drug effects*; D011441:Propylthiouracil / Q000494:pharmacology; D013961:Thyroid Gland / Q000187:drug effects* / Q000503:physiopathology; D013974:Thyroxine / Q000494:pharmacology
chemical_list: D013956:Antithyroid Agents; D006727:Hormone Antagonists; D011441:Propylthiouracil; D013974:Thyroxine