Immunohistochemical localization of estrogen receptor alpha (ERα) in the oviduct of Indian buffalo during follicular and luteal phases of estrous cycle.

The localization and distribution of estrogen receptor alpha (ERα) in different segments of oviduct of buffalo during follicular and luteal phases of estrous cycle were investigated using immunohistochemistry. Tissue samples from the different segments of oviduct from 12 buffaloes (six each during follicular and luteal phases of estrous cycle) were collected from slaughter house after assessing the gross morphology of ovaries. In addition, blood samples were collected from the animals before slaughter to estimate levels of estrogen and progesterone hormones. The tissue distribution of estrogen receptor was determined by immunohistochemical technique using one-step polymer HRPO staining system. The estrogen receptor was localized in the lamina epithelialis, propria submucosa, tunica muscularis, and tunica serosa. The maximum localization was observed in the lamina epithelialis, where both ciliated and secretory cell types were positive for ERα. Percentage of positive cells varied during the follicular and luteal phases of estrous cycle. The lining epithelium of oviductal glands was also intensely positive for ERα. No immunostaining was observed in any tunic of the oviduct when the primary antibody was replaced by antibody diluent or buffer, and it served as negative control. The data showed that highest immune positive cells were observed in the ampulla region of the oviduct and these cells were lowest in the utero-tubal junction (p < 0.05). Infundibulum, ampulla, and isthmus showed a higher percentage of ERα-positive cells during follicular phase of estrous cycle as compared with those of the luteal phase of estrous cycle (p < 0.05). There was no significant difference in the percentage positive cells during the two phases of estrous cycle in the utero-tubal junction. Immunogold labeling with anti-ERα antibody confirmed the findings of immunohistochemical study at subcellular level. The higher expression during the follicular phase was directly correlated with the level of estrogen hormone.