Estrogen receptors are present in the epididymis of the rooster

Our recent discovery that testicular germ cells and epididymal sperm contain active P450 aromatase suggests that the reproductive tract may be a target for estrogen. Therefore, the objective of this study was to determine if estrogen receptors (ER) are present in the avian epididymis using immunocytochemistry, northem blot analysis, and in situ hybridization. Immunoperoxidase staining for ER was found principally in nuclei of nonciliated epithelial cells of proximal and distal efferent ductules and the epididymis duct. The ciliated cells also appeared to be slightly positive in the efferent ductules. Weak immunostaining was also observed in the connective tissue of the epididymis duct. Immunostaining was more intense in epithelial cells of the efferent ductules than in epithelial cells of the epididymal duct or connective tissue cells. Strong specific hybridization signals for ER mRNA corresponded to the same areas exhibiting immunocytochemical localization. The presence of ER mRNA in the epididymis was confirmed by northem blot analysis, which showed a single band corresponding to approximately 7.8 kb, similar to that found in chicken oviduct. Based on these data, we suggest that the efferent ducts of the rooster are a primary target for estrogen and that estrogen may have a role in the regulation of avian epididymal function.