17α-甲基睾酮对稀有鮈鲫幼鱼性腺发育与血清卵黄蛋白原水平的影响

Influences of 17α-methyltestosterone on Gonad Development and Plasma Vitellogenine Induction of Rare Minnow Larva

17α-甲基睾酮是一种人工合成雄激素,在水产养殖以及医药行业中广泛使用,其对鱼类的内分泌干扰效应研究工作相对较少.通过甲基睾酮对稀有鲫幼鱼的42天流水暴露,观察了其性腺发育和生物标记物变化.在500ng·L-1甲基睾酮暴露组中幼鱼生长受到抑制(p≤0.05),在50ng·L-1以上暴露组中性腺指数显著增加(p≤0.05),雄性个体比率明显升高.通过组织学观察发现,50ng·L-1以上浓度甲基睾酮暴露后卵巢组织切片中出现了精子细胞,且精子细胞数量随剂量的增加而增加.通过生物标记物卵黄蛋白原测定发现,在50ng·L-1以上浓度甲基睾酮暴露后,稀有鲫幼鱼血清中的卵黄蛋白原水平显著增加(p≤0.05).综合分析,17α-甲基睾酮主要表现出雄激素效应,而其在稀有鲫体内的代谢物则能够应激卵黄蛋白原,对稀有鲫幼鱼的最低可观察效应浓度(LOEC)为50ng·L-1.因此,仅依靠体内卵黄蛋白原应激单项指标不能准确判定化学品是否是环境类雌激素.

17α-methyltestosterone, an anabolic steroid, was used widely in aquaculture and medicine. However, few work has been done on the environmental endocrine disrupting of this chemical. In present study, larva of rare minnow was continuously exposed to 17α-methyhestosterone for 42 days. Gonad development and levels of plasma vitellogenine were measured. The results showed that the growth was inhibited at exposure concentration higher than 500ng·L^-1 （p ≤ 0.05） , and gonadosomatic index （GSI） was significantly increased at concentration higher than 50ng·L^-1 （p≤ 0.05） . Sex ratio was alternated and male fishes were significantly more than females when exposure concentration higher than 50ng·L^-1. Also at exposure levels higher than 50ng·L^-1, testis-ova phenomena were observed and numbers of testis-ova increased with exposure concentration. Also, levels of plasma vitellogenine in immature fishes increased significantly （p≤0.05） and there was not a dose-dependent manner when exposure concentration higher than 50ng·L^-1. Our conclusion is that 17α-methyltestosterone manifests mainly androgenic effects, but its metabolic products could induce plasma vitellogenine induction, the Lowest Observed Effect Concentration （LOEC） is about 50ng·L^-1. Therefore, identification of environmental estrogens based merely on vitellogenine induction could result in the wrong conclusion.