Seasonal expressions of androgen receptor, estrogen receptors, 5 alpha-reductases and P450arom in the epididymis of the male muskrat (Ondatra zibethicus)

摘要

The steroid hormones not only exert various endocrine functions but also act as the autocrine or paracrine factors in different tissues of mammals. In the present study, the seasonal expressions of androgen receptor (AR), estrogen receptors alpha and beta (ER alpha and ER beta), aromatase cytochrome P450 (P450arom) and 5 alpha-reductase 1, 2 were investigated in the epididymis of the muskrat. HE staining showed enlarged lumen and abundant sperm in the breeding season while reduced lumen with no sperm in the non-breeding season. The staining of AR was presented in nuclei of epithelial cells of the epididymis in both seasons. The immunostaining of ERa was localized in both nuclei and cytoplasm of epithelial cells of the epididymis during the breeding season, while the weak staining of ERa was only in the nuclei of epithelial cells during the non-breeding season. In contrast, ER beta signal was negative in the epididymis of the muskrat in both seasons. The positive signals for P450arom and 5 alpha-reductase 1, 2 were found in the cytoplasm of epithelial and smooth muscle cells during both seasons. Moreover, the protein and mRNA expression levels of AR, ERa, P450arom and 5 alpha-reductase 1, 2 were significantly higher in the epididymis during the breeding season than those of the non-breeding season, and the expression level of 5 alpha-reductase 1 was higher when compared with 5 alpha-reductase 2. In addition, the levels of testosterone (T) and dihydrotestosterone (DHT) in the epididymis and serum were remarkably higher during the breeding season. Taken together, these findings suggested androgen and estrogen might play an important endocrine or autocrine/paracrine role to regulate the epididymal functions of the muskrat.