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采用组织学和荧光实时定量PCR方法,检测饲喂不同剂量芳香化酶抑制剂来曲唑(letrozole,50、100和200μg/g)对胡子鲇(Clarias fuscus)性腺组织学和性别比率的影响,以及200μg/g来曲唑对性分化前后脑型芳香化酶基因(Cyp19a1b)和翼状螺旋/叉头转录因子2(Foxl2)基因表达的影响,结果表明,50μg/g剂量的来曲唑对胡子鲇性腺分化无显著影响;但100μg/g和200μg/g剂量的来曲唑可促进胡子鲇精巢分化,抑制卵巢分化,卵巢腔最早出现时间和初级卵母细胞出现时间均分别推迟3 d和6 d,而初级精母细胞最早出现时间则分别提前2 d和5 d,且雄性率分别达65.8%和71.3%,显著高于50μg/L组和对照组(P<0.05)。胡子鲇性腺分化前(出膜后12 d),Cyp19a1b和Foxl2基因即开始表达,性腺分化前后Cyp19a1b相对表达量无显著差异(P>0.05),但Foxl2相对表达量则随性分化而逐渐降低,且来曲唑显著抑制性腺分化过程中Cyp19a1b和Foxl2的表达(P<0.05)。结果表明,100μg/g以上剂量的来曲唑可有效诱导胡子鲇分化为雄性;Cyp19a1b可能不直接参与胡子鲇性腺分化,但Foxl2直接参与此过程。
The histological and sex ratio of gonads of Clarias fuscus were detected by using histological and real-time fluorescence quantitative PCR at different doses of letrozole (50, 100 and 200 μg / g) And the effects of 200μg / g Letrozole on the expression of Cyp19a1b and Foxl2 genes before and after sexual differentiation. The results showed that letrozole 50μg /鲇 gonadal differentiation had no significant effect; However, letrozole 100μg / g and 200μg / g dose can promote the differentiation of beard 鲇 spermophilia, inhibit ovarian differentiation, the earliest ovarian cavity emergence time and primary oocyte were delayed 3 d and 6 d, while the primary spermatocytes appeared two days earlier and 5 days respectively, with the male rates of 65.8% and 71.3%, respectively, which were significantly higher than those of 50μg / L group and control group (P <0.05). The expression of Cyp19a1b and Foxl2 began to be expressed before and after gonadal differentiation (12 d after the film formation), while the relative expression of Cyp19a1b before and after gonadal differentiation had no significant difference (P> 0.05) Letrozole significantly inhibited the expression of Cyp19a1b and Foxl2 during gonadal differentiation (P <0.05). The results showed that letrozole at a dose of 100μg / g could effectively induce the differentiation of male beard into male; Cyp19a1b may not be directly involved in the gonad differentiation of beard, but Foxl2 directly involved in this process.