Seasonal Expression Of Androgen Receptor, Aromatase,and Estrogen Receptor Alpha And Beta In The Testisand Epididymis Of The Wild Ground Squirrel

The wild ground squirrel (Citellus dauricus Brandt) is a typical seasonal breeder which has a strict and extremely compressed breeding period from April to May, a long period of sexual dormancy from June to the following March, and a 6-month hibernation (from October to March). The testis and epididymis of this species exhibits a distinct seasonal morphology changes from the breeding season to the nonbreeding season. In mammalian, testosterone appears to be responsible for maintaining adequate blood-testis barrier function, inducing meiosis and postmeiotic development of germ cells and inhibition of germ cell apoptosis. The aim of this study was to investigate the seasonal expression of androgen receptor (AR), estrogen receptors α and β (ERα and ERβ) and aromatase cytochrome P450 (P450arom) mRNA and protein by real-time PCR and immunohistochemistry in the wild ground squirrel testes and epididymis. Histologically, all types of spermatogenic cells including mature spermatozoa were identified in the breeding season (April), while spermatogonia and primary spermatocytes were observed in the nonbreeding season (June), and spermatogonia, primary spermatocytes and secondary spermatocytes were found in pre-hibernation (September). The epididymis in breeding season has bigger size than other periods. AR was present in Leydig cells, peritubular myoid cells and Sertoli cells in the breeding season and pre-hibernation with more intense staining in the breeding season, whereas AR was only found in Leydig cells in the nonbreeding season; in epididymis, AR was shown in the all the period, but the stronger staining was detected in the breeding season. P450arom was expressed in Leydig cells, Sertoli cells and germ cells in testes during the breeding season, whereas P450arom was found in Leydig cells and Sertoli cells during pre-hibernation, but P450arom was not present in the nonbreeding season; In epididymis, there were immunestaining in the epididymis epithelium around the year. Stronger immunohistochemical signal for ERα was present in Sertoli cells and Leydig cells during the breeding season; ERβ was only expressed in Leydig cells in testes of the breeding season. Consistent with the immunohistochemical results, the mean mRNA level of AR, P450arom, ERa and ERβ were higher in the testes and epididymis of the breeding season when compared to pre-hibernation and the nonbreeding season. These results suggested that the seasonal changes in spermatogenesis and recrudescence and regression process of testes and epididymis in WGSs might be correlated with expression levels of AR, P450arom and ERs, and estrogen and androgen may play important autocrine/paracrine roles to regulate seasonal testicular function.