Seasonal expressions of androgen receptor, P450arom and estrogen receptors in the epididymis of the wild ground squirrel (Citellus dauricus Brandt)

The aim of this study was to investigate the seasonal expressions of androgen receptor (AR), estrogen receptors alpha and beta (ER alpha and ER beta) and aromatase cytochrome P450 (P450arom) in the epididymis of the wild ground squirrel. Histologically, the epididymis was with larger duct diameter and cell population during the breeding season. AR was presented in the peritubular smooth muscle cells and epithelial cells in the whole epididymis with stronger staining in the breeding period. P450arom was intensely localized in epithelial cells and spermatozoa during the breeding season, absent in the non-breeding season and moderately stained in pre-hibernation. During the breeding season, ER alpha was intensely expressed in epithelial cytoplasm and/or nucleus, whereas in the non-breeding season and pre-hibernation, weaker staining signal was found in nucleus of epithelial cells. ER beta was absent in the entire annual cycle by immunohistochemical and Real-time PCR detection. The mRNA levels of AR, P450arom and ER alpha were higher in the epididymis of the breeding season when compared to those of the non-breeding season and pre-hibernation. Taken together, these results suggest that epididymis of the wild ground squirrel is a primary target for androgen and estrogen, and the expression of P450arom represents that epididymis may be a potential source of estrogen.