AMPHIBIAN DEVELOPMENT, GROWTH AND REPRODUCTION ASSAY USING XENOPUS TROPICALIS AND IN VITRO ESTROGEN RECEPTOR TRANSACTIVATION ASSAY
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1
National Institute for Basic Biology, Okazaki Institute for Integrative Biosceince, Japan
Amphibian Development, Growth and Reproductive Assay (ADGRA) possibly detect the adverse effects of chemicals on larval development and sexual differentiation. US Environmental Protection Agency (USEPA) and Ministry of the Environment, Japan are collaboratively establishing a short life cycle test using Xenopus (Silurana) tropicalis which has been proposed to OECD (Organization for Economic Cooperation and Development) for evaluation of chemicals. In this study, X. tropicalis (NF stage-45, 48 h after fertilization) were exposed to 3, 10 and 30ng/L 17α-ethynylestradiol (EE2) for 40 weeks: actual concentration of EE2 measured 2.7, 8.6, 26.8 ng/L, respectively. Sub-samplings were carried out at completion of metamorphosis (6-7 week after exposure) and juvenile stage (15 weeks after exposure). Starting from lowest (3ng/L), increased EE2 concentration had a correlative induction of plasma vitellogenin (VTG) level in both larva (mixed sex) and male adults. However, significantly elevated % phenotypic female population in larvae, adults and genotypic males were observed beyond 10ng/L EE2. Juveniles and adults males of 10ng/L treatment group having nuptial pad were reduced significantly, whereas occurrence of male carrying oviduct were increased. Sperm count was decreased at only 30ng/L EE2 treatment group. Interestingly, withdrawal of EE2 exposure at 15 week was failed to change the reduction in sex ratio and nuptial pad development at 40 weeks. Phenotypic males had testis-ova at 3ng/L EE2, which corresponds to the lowest effective concentration (LOEC) of plasma VTG induction, a biomarker for estrogenic toxicity. Furthermore, comparing these data with present in vitro reporter gene assay, it can be hypothesized that LOEC of ADGRA corresponds to EC50 values of EE2 transcriptional activity by X. tropicalis ERα. The present test may prove helpful for a establishing a short-term reproduction assay in the future.
Acknowledgements
Supported by grants from the Ministry of the Environment, Japan.
Keywords:
estrogen receptor,
ethinylestradiol,
OECD amphibian reproduction test,
Sex reversal,
testis-ova,
transactivation assay,
vitellogenin,
Xenopus tropicalis
Conference:
ISAREN 2011: 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology, Ann Arbor, United States, 11 Jul - 13 Jul, 2011.
Presentation Type:
Invited Symposium
Topic:
Reproduction
Citation:
Iguchi
T
(2011). AMPHIBIAN DEVELOPMENT, GROWTH AND REPRODUCTION ASSAY USING XENOPUS TROPICALIS AND IN VITRO ESTROGEN RECEPTOR TRANSACTIVATION ASSAY.
Front. Endocrinol.
Conference Abstract:
ISAREN 2011: 7th International Symposium on Amphibian and Reptilian Endocrinology and Neurobiology.
doi: 10.3389/conf.fendo.2011.03.00022
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Received:
22 Jul 2011;
Published Online:
09 Aug 2011.
*
Correspondence:
Prof. Taisen Iguchi, National Institute for Basic Biology, Okazaki Institute for Integrative Biosceince, Okazaki, Aichi, 444-8787, Japan, taisen@nibb.ac.jp