Hirai Narisato, Nanba Ayumi, Koshio Masaaki, Kondo Takuya, Morita Masatoshi, Tatarazako Norihisa
National Institute for Environmental Studies, Onogawa 16-2, Tsukuba 305-8506, Japan.
Aquat Toxicol. 2006 Apr 20;77(1):78-86. doi: 10.1016/j.aquatox.2005.11.001. Epub 2005 Dec 2.
Gonad histological changes were examined in Japanese medaka exposed to 17beta-estradiol (E2) during early-life stages. Two experiments were conducted at different concentrations of E2 (33.5 and 140.6 ng/L, mean value of measurement) and larvae and juveniles were observed for histological changes in the gonad. Differentiation of ovary and testis in control fish was apparent 12 days post-hatch (dph). At 12 dph, normal testes were observed in male fish that had been exposed to 33.5 ng/L E2, but at 14 and 20 dph, testis-ova was recognized in male fish. Male fish exposed to 140.6 ng/L E2 had testis-ova at 12 dph and gradual transformation to ovary was observed in male fish until 20 dph. In both experiments, the ovarian tissue in testis of male fish exposed to E2 was frequently distributed along the central transverse axis of the gonad, expanding into the transverse axis. The results indicated that 17beta-estradiol can induce testis-ova in male medaka during the larval period and sex-transformation is more frequent at higher (140.6 ng/L) than lower concentrations (33.5 ng/L) of estradiol. The results also demonstrated that testis-ova first appear in the central area of the transverse axis of testis.
在日本青鳉鱼幼鱼期暴露于17β-雌二醇（E2）的情况下，对其性腺组织学变化进行了研究。在不同浓度的E2（测量平均值为33.5和140.6 ng/L）下进行了两项实验，并观察了幼鱼和成鱼性腺的组织学变化。对照鱼在孵化后12天（dph）卵巢和精巢的分化明显。在12 dph时，暴露于33.5 ng/L E2的雄鱼观察到正常精巢，但在14和20 dph时，雄鱼中发现了精巢-卵巢。暴露于140.6 ng/L E2的雄鱼在12 dph时出现精巢-卵巢，并且在20 dph之前观察到雄鱼逐渐向卵巢转变。在两个实验中，暴露于E2的雄鱼精巢中的卵巢组织经常沿性腺的中央横轴分布，并向横轴扩展。结果表明，17β-雌二醇可在幼鱼期诱导雄鱼出现精巢-卵巢，且在较高浓度（140.6 ng/L）雌二醇下比在较低浓度（33.5 ng/L）下性转变更频繁。结果还表明，精巢-卵巢首先出现在精巢横轴的中央区域。
