Greytak Sarah R, Champlin Denise, Callard Gloria V
Department of Biology, Boston University, Boston, MA 02215, USA.
Aquat Toxicol. 2005 Mar 4;71(4):371-89. doi: 10.1016/j.aquatox.2004.12.007.
Populations of killifish (Fundulus heteroclitus) persist in many different highly polluted environment indicative of adaptation or tolerance. In this study, we sought to determine whether long term, multigenerational exposures to environmental contaminants has affected reproductively relevant genes and biological processes. A homology cloning strategy was used to isolate the killifish cytochrome P450 aromatase (P450arom, estrogen synthetase) cDNAs. Consistent with previous fish studies, killifish were found to have two P450arom forms, which segregated into A- and B-gene clades and were differentially expressed in brain (B >> A) and ovary (A >> B). Comparison of killifish from highly polluted (New Bedford Harbor, NBH) and unpolluted (Scorton Creek, SC) environments revealed no site-related differences in P450arom coding sequences or in overall tissue distribution patterns. As measured by real-time quantitative PCR (QPCR) analysis, however, P450arormB (a known marker of estrogen effect) was approximately two-fold higher in the brain of NBH than of SC fish, a difference seen in reproductively active and inactive males and females. Providing further evidence of exposure to estrogen-like pollutants or metabolites in NBH, vitellogenin (vtg) mRNA and protein were elevated in seasonally active and inactive males, and in reproductively inactive females, when compared to SC fish. By contrast, during the period of reproductive activity, NBH females had a lower gonadosomatic index, lower plasma estrogen, a decreased hepatosomatic index, and reduced vtg expression as compared to SC females, indicating that the female hypothalamic-pituitary-gonadal (HPG)-liver axis is impaired in the polluted environment. As measured by a decrease in plasma androgen (but not GSI), the male HPG axis was impaired in reproductively active NBH versus SC fish. In agreement with reports that NBH killifish are resistant to dioxin-like chemicals (DLC) that activate arylhydrocarbon receptor (AhR) signaling, ovarian P450aromA (a marker of dioxin-like effect in zebrafish embryos) did not differ in SC and NBH fish. In conclusion, the killifish population at the NBH Superfund site maintains a level of reproductive competence in the face of evidence of exposure to estrogen-like pollutants and endocrine disruption.
鳉鱼（Fundulus heteroclitus）种群在许多不同的高度污染环境中持续存在，这表明它们具有适应性或耐受性。在本研究中，我们试图确定长期多代暴露于环境污染物是否影响了与生殖相关的基因和生物学过程。采用同源克隆策略分离鳉鱼细胞色素P450芳香化酶（P450arom，雌激素合成酶）cDNA。与之前的鱼类研究一致，发现鳉鱼有两种P450arom形式，它们分为A基因和B基因分支，在脑（B >> A）和卵巢（A >> B）中差异表达。对来自高度污染（新贝德福德港，NBH）和未污染（斯科顿溪，SC）环境的鳉鱼进行比较，结果显示P450arom编码序列或整体组织分布模式没有与地点相关的差异。然而，通过实时定量PCR（QPCR）分析测量，NBH鳉鱼脑中的P450aromB（雌激素效应的已知标志物）比SC鳉鱼高约两倍，这种差异在生殖活跃和不活跃的雄性和雌性中均可见。与SC鳉鱼相比，NBH季节性活跃和不活跃的雄性以及生殖不活跃的雌性中卵黄蛋白原（vtg）mRNA和蛋白升高，这进一步证明了NBH中存在类似雌激素的污染物或代谢物暴露。相比之下，在生殖活动期间，与SC雌性相比，NBH雌性的性腺体指数较低、血浆雌激素水平较低、肝体指数降低且vtg表达减少，这表明在污染环境中雌性下丘脑 - 垂体 - 性腺（HPG） - 肝脏轴受损。通过血浆雄激素水平降低（但不是GSI）来衡量，生殖活跃的NBH鳉鱼与SC鳉鱼相比，雄性HPG轴受损。与NBH鳉鱼对激活芳烃受体（AhR）信号的二噁英类化学物质（DLC）具有抗性的报道一致，SC和NBH鳉鱼卵巢中的P450aromA（斑马鱼胚胎中二噁英类效应的标志物）没有差异。总之，面对存在类似雌激素的污染物暴露和内分泌干扰的证据，NBH超级基金场地的鳉鱼种群维持了一定水平的生殖能力。
