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Environmentally Relevant Concentrations of Ethynylestradiol Cause Female-Biased Sex Ratios in Xenopus tropicalis and Rana temporaria
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
2007 (English)In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 26, no 5, 1005-1009 p.Article in journal (Refereed) Published
Abstract [en]

The susceptibility of Xenopus (Silurana) tropicalis and Rana temporaria to ethynylestradiol (EE2), a potent estrogenic pharmaceutical and environmental pollutant, was investigated. Larval EE2 exposure caused female-biased sex ratios at concentrations as low as 0.06 nM, which is comparable to levels found in the environment. The susceptibility of the two frog species to EE2 was comparable, supporting the use of X. tropicalis as a model organism for research on developmental reproductive toxicity of estrogenic pollutants.

Place, publisher, year, edition, pages
2007. Vol. 26, no 5, 1005-1009 p.
Keyword [en]
Amphibians, Endocrine disruption, Estrogen, Gonadal differentiation, Test system
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-97446DOI: 10.1897/06-464R.1ISI: 000245749500024PubMedID: 17521149OAI: oai:DiVA.org:uu-97446DiVA: diva2:172401
Available from: 2008-09-05 Created: 2008-09-05 Last updated: 2013-09-06Bibliographically approved
In thesis
1. Endocrine Disruption in Amphibians: Developmental Effects of Ethynylestradiol and Clotrimazole on the Reproductive System
Open this publication in new window or tab >>Endocrine Disruption in Amphibians: Developmental Effects of Ethynylestradiol and Clotrimazole on the Reproductive System
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Amphibian populations are declining world-wide and one of the suggested reasons is environmental pollutants. Studies of long-term effects on the reproductive system in frogs following larval exposure to environmental pollutants are scarce. It is therefore important to develop methods to study developmental reproductive toxicity in amphibians. In this thesis the usefulness of Xenopus tropicalis (the West African clawed frog) as a model species for a test system was investigated. Effects on the reproductive system after larval exposure to the pharmaceuticals ethynylestradiol (EE2) and clotrimazole were evaluated. The susceptibility to EE2 exposure was compared between the model species and a wild species, the European common frog (Rana temporaria). Larval exposure to EE2 caused female-biased sex ratios in both examined frog species, indicating male-to-female sex-reversal. In adult Xenopus tropicalis, male frogs that were not sex-reversed had reduced fertility and decreased amount of mature spermatozoa in the seminiferous tubules. The proportion of frogs with ovaries but lacking oviducts increased with increasing EE2-concentrations. A female frog without oviducts is sterile. The development of ovaries in sex-reversed male frogs was implied to be similar to control females. The combination of a reduced number of males, due to sex-reversal, and impaired fertility could have severe effects on frog populations. Larval exposure to clotrimazole modulated aromatase activity in gonads and brain in Xenopus tropicalis. Brain aromatase activity was decreased at the time for gonadal differentiation and gonadal aromatase activity was increased at metamorphosis. The findings in this thesis indicate that reproduction in wild frogs might be impaired by estrogenic compounds in the environment. The results combined with the short generation time supports the use of Xenopus tropicalis as a model species when evaluating long term effects of endocrine disruptors on the reproductive system in amphibians.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 57 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 545
Keyword
Test system, Xenopus tropicalis, Rana temporaria, sex ratio, sex differentiation, fertility, aromatase, ovary, testis, oviduct
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-9209 (URN)978-91-554-7260-3 (ISBN)
Public defence
2008-09-26, Lindahlsalen, Evolutionsbiologisk centrum (EBC), Norbyvägen 18A, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2008-09-05 Created: 2008-09-05 Last updated: 2013-09-06Bibliographically approved

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