Expression of the progesterone receptor in the Thai swamp buffalo oviduct at the follicular and luteal phases.

The objective of this study was to investigate the presence and distribution of the progesterone receptor (PR) in the Thai swamp buffalo oviduct at the follicular (n=10) and luteal phases (n=12). Reproductive tracts from mature female Thai swamp buffaloes were collected from a local slaughterhouse. Both ovaries were examined for the phase of estrous cycle and the oviducts were separated into the uterotubal junction (UTJ), the isthmus, the ampulla and the infundibulum. Tissue samples were subjected to immunohistochemical staining to assess the localization of PR in the epithelium, subepithelial connective tissue and smooth muscle. A positive nuclear immunolabeling of PR was detected in all three compartments of the buffalo oviduct and the average staining was influenced by the phase of the estrous cycle. There was more intensity (p<0.05) and a larger proportion (p<0.05) of PR immunostaining during the follicular phase than that during the luteal phase in the UTJ and the isthmus. However, the tendency of PR was also greater in the ampulla and infundibulum at the follicular phase. Noticeably, nuclear PR staining was more commonly detected in the secretory cells than in the ciliated cells. In conclusion, the results of this study suggest that PR expression was clearly detected in Thai swamp buffalo oviduct and varied according to the oviductal segment as well as with the marked changes in the period of estrous cycle.