Initiation of the expression of peroxisome proliferator - activated receptor gamma (PPAR gamma) in the rat ovary and the
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BioMed Central
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Initiation of the expression of peroxisome proliferator - activated receptor gamma (PPAR gamma) in the rat ovary and the role of FSH Mary J Long1, M Ram Sairam2 and Carolyn M Komar*1,3 Address: 1Department of Animal Science, Iowa State University, Ames, IA 50011, USA, 2Molecular Reproduction Research Laboratory, Institut de Recherches Cliniques de Montreal Montreal, Quebec, H2W 1R7, Canada and 3Department of Biomedical Sciences, West Virginia School of Osteopathic Medicine, Lewisburg, WV 24901, USA Email: Mary J Long - [email protected]; M Ram Sairam - [email protected]; Carolyn M Komar* - [email protected] * Corresponding author
Published: 7 December 2009 Reproductive Biology and Endocrinology 2009, 7:145
doi:10.1186/1477-7827-7-145
Received: 30 October 2009 Accepted: 7 December 2009
This article is available from: http://www.rbej.com/content/7/1/145 © 2009 Long et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract PPARgamma is highly expressed in granulosa cells by 23 days post-partum (pp) and is downregulated in response to the LH surge. We tested the hypothesis that high levels of FSH during the neonatal period trigger the expression of PPARgamma. To determine when PPARgamma expression is initiated, ovaries were collected from neonatal rats. Messenger RNA for PPARgamma was undetectable on day 1, low from days 5-14, and increased by day 19 pp (p < 0.05). PPARgamma was detected in select granulosa cells in primary/early secondary follicles. Messenger RNA for the FSH receptor was detected as early as day 1 and remained steady throughout day 19 pp. The FSH receptor was detected by immunoblot analysis in ovaries collected 1, 2, and 5-9 days pp. In a subsequent experiment, neonatal rats were treated with acyline (GnRH antagonist) which significantly reduced FSH (p < 0.05) but not levels of mRNA for PPARgamma. The role of FSH in the induction of PPARgamma expression was further assessed in ovarian tissue from FORKO mice. Both mRNA and protein for PPARgamma were identified in ovarian tissue from FORKO mice. In summary, the FSH/FSH receptor system is present in granulosa cells prior to the onset of expression of PPARgamma. Reducing FSH during the neonatal period, or the ability to respond to FSH, did not decrease expression of mRNA for PPARgamma. These data indicate that FSH is not a primary factor initiating the expression of PPARgamma and that other agents play a role in activating its expression in the ovary.
Background
Peroxisome proliferator-activated receptor γ (PPARγ) is a member of the steroid receptor superfamily. This transcription factor heterodimerizes with the 9, cis-retinoic acid receptor (RXR) and binds to a short sequence of DNA, a PPAR response element (PPRE), present in the promoter region of targ
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