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Selective activation of estrogen receptor alpha in Japanese quail embryos affects reproductive organ differentiation but not the male sexual behavior or the parvocellular vasotocin system
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.
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2008 (English)In: General and Comparative Endocrinology, ISSN 0016-6480, Vol. 159, no 2-3, 150-157 p.Article in journal (Refereed) Published
Abstract [en]

Estradiol is crucial for normal female differentiation in birds. Developmental effects of estrogen are believed to be mediated by slow genomic actions through the nuclear estrogen receptors alpha (ERα) and/or beta (ERβ). Consequently, exogenous compounds that interfere with the ERs may disrupt sexual differentiation of the reproductive organs and of the brain areas controlling sexual behaviors. The present study was conducted to elucidate the role of ERα in xenoestrogen-induced disruption of sexual differentiation in the Japanese quail (Coturnix japonica). Embryonic treatment with the synthetic estrogen, ethinylestradiol (EE2), and with the ERα-selective agonist, propyl pyrazole triol (PPT), induced oviductal malformations in females and retention of oviducts in males. Both EE2 and PPT caused weight asymmetry between left and right testes and reduced the cloacal gland area in males. EE2 significantly reduced the copulatory behavior in males whereas PPT had no effect on this behavior. The sexually dimorphic parvocellular vasotocin-immunoreactive (VT-ir) system in the medial preoptic nucleus (POM), the lateral septum (SL) and the medial part of the nucleus of the stria terminalis (BSTm), was not affected by EE2 or PPT. Our results suggest that xenoestrogen-induced effects on reproductive organ differentiation are mediated by ERα, whereas demasculinization of male copulatory behavior and the VT-ir system appears not to be induced by activation of ERα alone.

Place, publisher, year, edition, pages
2008. Vol. 159, no 2-3, 150-157 p.
Keyword [en]
Japanese quail, Estrogen receptor, Sex differentiation, Sexual behavior, Vasotocin
National Category
Endocrinology and Diabetes
Identifiers
URN: urn:nbn:se:uu:diva-97340DOI: 10.1016/j.ygcen.2008.08.012ISI: 000261356300006OAI: oai:DiVA.org:uu-97340DiVA: diva2:172232
Available from: 2008-05-22 Created: 2008-05-22 Last updated: 2012-02-03
In thesis
1. Roles of ERα and ERβ in Normal and Disrupted Sex Differentiation in Japanese Quail
Open this publication in new window or tab >>Roles of ERα and ERβ in Normal and Disrupted Sex Differentiation in Japanese Quail
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Exposure to xenoestrogens during development has been shown to impair sexual differentiation in various species. The major aim of this thesis was to elucidate the respective roles of the two estrogen receptors ERα and ERβ in normal and disrupted differentiation of sex organs and copulatory behavior in the Japanese quail (Coturnix japonica). The expression of ERα mRNA was much stronger than that of ERβ mRNA in the gonads and Müllerian ducts (embryonic oviducts) in early embryos. By contrast, ERβ seemed to be predominantly expressed in regions of the embryonic brain that are associated with male sexual behavior. Embryos were exposed to the selective ERα agonists propyl-pyrazole-triol (PPT) and 16α-lactone-estradiol (16α-LE2). The estrogens 17β-estradiol (E2) and 17α-ethynylestradiol (EE2), which activate both ERα and ERβ, were used as positive controls. All substances impaired reproductive organ differentiation. The effects observed included oviductal malformations in females and partial development of oviducts in males. All substances also induced testis feminization (ovotestis) in male embryos. The male copulatory behavior was severely impaired by the positive controls but was unaffected by PPT and 16α-LE2 at doses that disrupted sex organ differentiation. A higher dose of 16α-LE2 significantly suppressed the behavior. However, it is possible that this effect was caused by cross-activation of ERβ. The substances also induced hepatic expression of mRNA encoding the egg-yolk proteins vitellogenin II and very low-density apolipoprotein II, which are commonly used as indicators of estrogen exposure. In conclusion, the results suggest that ERα is important for female reproductive organ differentiation. Excess activation of ERα by xenoestrogens impairs differentiation in both females and males and induces hepatic expression of egg-yolk proteins. The results also indicate that ERα alone cannot mediate demasculinization of male copulatory behavior in quail, although further studies are needed to test this hypothesis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 68 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 445
Keyword
Toxicology, sex differentiation, estrogen receptor, sexual behavior, endocrine disruption, Japanese quail, Toxikologi
Identifiers
urn:nbn:se:uu:diva-8921 (URN)978-91-554-7232-0 (ISBN)
Public defence
2008-06-12, Lindahlsalen, Evolutionsbiologiskt centrum (EBC), Norbyvägen 18A, Uppsala, 13:15 (English)
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Available from: 2008-05-22 Created: 2008-05-22 Last updated: 2010-01-07Bibliographically approved

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