Seasonal Expressions Of Androgen Receptor,Estrogen Receptor ? And ?,5?-reductase 1 And 2,P450 Arom In The Epididymis Of The Muskrat(Ondatra Zibethicus)

Seasonal reproduction of animal is a kind of reproduction phenomenon that occurs only in a specific season when animals adapt to the change of natural environment.Most wild mammals have the characteristics of seasonal reproduction,and some domesticated wild mammals also retain their seasonal breeding characteristics.The muskrat is a domesticated wild mammal with obvious seasonal reproduction which enters the breeding season in March and enters the non-breeding season in November.Along with changes in seasonal activities,the genital organs of the muskrats,such as the testis and the epididymis,undergo significant changes in morphology and functions.Our previous studies have shown that seasonal changes in testicular functions in the muskrat were regulated by androgen and estrogen,which are important for spermatogenesis in the testis and sperm maturation in the epididymis.In order to understand the seasonal changes of the epididymis of the muskrat,we have qualitatively and quantitatively analyzed the histological and morphological changes of the epididymides,detected the seasonal expression and expression level changes of androgen receptor(AR),estrogen receptor ? and ?(ERa,ER?),5?-reductase 1 and 2,cytochrome P450aromatase(P450arom)in the epididymis of the male muskrat.Results showed:morphologically,the weight and length of epididymis in the breeding season were significantly higher than those in the non-breeding season.In the breeding season,the lumen diameter and epithelial thickness of epididymis increased significantly,the thickness of lamina propria decreased,and there were a large number of sperms in the lumen.However,in the non-breeding season,the diameter of the lumen became significantly narrower,the epithelial height became thinner,the thickness of lamina propria increased,and there was no sperm in the lumen.Immunohistochemical results showed that the staining of AR was presented in nuclei of epithelial cells of the epididymis in both seasons,and the dyeing intensity during the breeding season was higher than the non-breeding season.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? signal was negative in the epididymis of the muskrat in both seasons.The positive signals for P450arom and 5?-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,ER?,P450arom and 5?-reductase 1,2 were significantly higher in the epididymis during the breeding season than those of the non-breeding season,and those were more intense during the breeding season.In addition,the levels of dihydrotestosterone(DHT)and testosterone(T)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.