双酚A对暗纹东方鲀幼鱼类固醇合成酶基因表达的影响

Bisphenol A modulates expression of sex steroid synthetase genes in Takifugu obscurus juveniles

为研究环境激素对养殖鱼类性别分化前后的内分泌干扰效应,分别将孵化后25 d(dph)的暗纹东方鲀(Takifugu obscurus)稚鱼和95 dph的幼鱼暴露于不同浓度双酚A(BPA)(0、50μg/L、200μg/L、1 000μg/L)3周和2周,用荧光定量PCR(QRT-PCR)方法检测编码性类固醇激素合成酶及相关因子的基因(STAR、CYP17a、CYP11b及CYP19a)表达。结果显示,BPA诱导了稚鱼STAR、CYP17a和CYP11b表达上调,且与浓度有正相关,而CYP19a表达在BPA 200μg/L和1 000μg/L浓度下分别暴露3周后显著下调。在幼鱼暴露组中,雌雄性腺发生不同的应答,精巢中STAR、CYP17a及CYP11b的表达出现先下调后上调,CYP19a则呈先受抑制后表达升高;在卵巢中STAR、CYP17a及CYP11b的表达先受抑制,随着时间的延长基因表达上调,CYP19a的表达受抑制。研究结果表明,BPA通过干扰性别分化初期暗纹东方鲀类固醇激素合成酶及相关因子的表达的而对性别分化产生影响;通过抑制雄性暗纹东方鲀中类固醇合成相关基因的表达而表现出内分泌干扰效应。对于雌鱼中类固醇合成相关基因的表达的影响则有波动性的变化,其作用机制仍需要进一步研究。

The abundance of Takifugu obscurus, an economically important wild fish species in China, has declined significantly in recent years. Bisphenol A（BPA） is an endocrine disrupting contaminant（EDC） that is ubiquitous in aquatic environments. It interferes with the growth, development, and reproduction of aquatic animals. Under normal conditions, sexual differentiation and reproductive development are controlled by sex hormones（estrogens and androgens） in fish. When present, EDCs upset the balance of hormones in the body and disrupt sexual differentiation. The effects of EDCs vary depending on the timing of exposure. Exposure during the embryo or juvenile stages can affect sexual differentiation and sex organ development. Conversely, exposure during the adult stages interferes with the organs or organ structure. We evaluated the effect of exposure to BPA（0, 50 μg/L, 200 μg/L, or 1 000 μg/L） in T. obscurus larvae（25 days post hatching; dph） and juveniles（95 dph） for 3 weeks and 2 weeks, respectively. We used fluorescent quantitative PCR（QRT-PCR） to quantify the level of STAR, CYP17 a, CYP11 b, and CYP19 a gene expression in the gonads. BPA exposure significantly up-regulated the expression of STAR and CYP17 a, up-regulated CYP11 b expression, and down-regulated CYP19 a gene expression. In juveniles, the expression of STAR, CYP17 a, and CYP11 b m RNA was first down-regulated and then up-regulated, relative to the control, following a change in CYP19 a expression. The effects in the ovary were more complex; BPA initially inhibited the expression of STAR, CYP17 a, and CYP11 b, but expression later increased significantly. BPA inhibited the expression of CYP19 a in the ovary. These data suggest that BPA exposure interfered with steroid synthesis in the early stages of sexual differentiation in T. obscurus. The expression of STAR and CYP17 a was up-regulated, thereby increasing steroid synthesis and altering the balance of estrogens and androgens. This change has an effect on sexual differentiation by interfering with the expression of CYP19 a and CYP11 b. BPA has an estrogenic effect in male T. obscurus by inhibiting steroidgenic gene expression, but there is a compensatory effect over time. Gene expression fluctuates in females, but the mechanism is currently poorly understood.