Localization of Immunoreactive Gonadotropin Releasing Hormone (GnRH) and Relative Expression of Its mRNA in the Oviduct During Pregnancy in Rats
Anamika Sengupta 1, Tabari Baker 1, Nilkanta Chakrabarti 1, Joseph A. Whittaker 1 and Rajagopala Sridaran 1*
1 Department of Physiology (AS,NC,RS) and Neuroscience Institute (TB,JAW), Morehouse School of Medicine, Atlanta, Georgia
* To whom correspondence should be addressed. E-mail: rsridaran{at}msm.edu.
Submitted on October 18, 2006
Accepted on 16 January 2007
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Abstract |
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This study was designed to determine the cellular and ultrastructural distribution of the gonadotropin releasing hormone (GnRH) and the relative expression of its mRNA in the oviduct of rats during different time points (days 7, 9, 16 and 20) of pregnancy. Immunofluorescent localization and confocal microscopic techniques were used to determine the cellular distribution of GnRH in the oviduct. Immunogold electron microscopy indicated its localization at the ultrastructural level and real time PCR was used to study the expression pattern of GnRH mRNA in the oviduct during pregnancy. In general, GnRH was localized within the epithelial cells lining the oviductal lumen at each selected time point. A strong correlation between the fluorescence intensity of GnRH immunoreactive cells and the relative expression of GnRH mRNA was noted on days 7 and 16, followed by a plateau by day 20. At the ultrastructural level, uniformed labeling of colloidal gold particles was observed in secretory vesicles and lamella of the luminal epithelium as well as the lumen of the oviduct. Collectively, these results, for the first time, demonstrate that the oviductal epithelium synthesizes and secretes the decapeptide GnRH during pregnancy in rats, which may have a possible role in post-implantation embryonic development and the maintenance of pregnancy.
Key Words:
GnRH, oviduct, pregnancy, rat