Regulation and expression of androgen receptor mRNA in rainbow trout at different stages of spermatogenesis

Gene expression of rainbow trout androgen receptor isoforms AR-alpha and AR-beta were quantified in the testis, liver and muscle of rainbow trout: (1) at different spermatogenic stages, and (2) after treatment with testosterone, estradiol or ovaprim. AR-alpha and AR-beta mRNA, as measured by real-time RT-PCR using the SYBR green dye method, shared similar expression patterns, but AR-beta tended to vary more dramatically both across the spermatogenic cycle and with sex hormone treatment. AR-alpha and AR-beta mRNA expression showed marked changes in the testis and muscle at different spermatogenic stages, peaking in spermiating fish, while no significant changes were observed in the liver. Regulation of AR mRNA by sex hormones, especially estradiol was tissue- and possibly stage-specific. A comparison of real-time and semi-quantitative RT-PCR showed similar results, however real-time was more sensitive and less variable. This study sheds light on the functional and evolutionary significance of the rainbow trout AR isoforms.