Poulsen Rikke, Luong Xuan, Hansen Martin, Styrishave Bjarne, Hayes Tyrone
Laboratory for Integrative Studies in Amphibian Biology, Department of Integrative Biology, University of California, Berkeley, CA 94720, USA; Toxicology Laboratory, Section of Advanced Drug Analysis, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
Laboratory for Integrative Studies in Amphibian Biology, Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
Aquat Toxicol. 2015 Nov;168:28-37. doi: 10.1016/j.aquatox.2015.09.008. Epub 2015 Sep 25.
A 27-day controlled exposure study of adult male African clawed frogs (Xenopus laevis) was conducted to examine the mechanism by which tebuconazole may disrupt steroidogenesis. The fungicide was measured by LC-MS/MS in tank water and in target tissues (adipose, kidney, liver, and brain), and we observed tissue-specific bioconcentration with BCF up to 238. Up to 10 different steroid hormones were quantified in gonads using LC-MS/MS and in plasma using GC-MS/MS and a radioimmunoassay was performed for further measurement of androgens. In order to assess whether effects increased with exposure or animals adapted to the xenobiotic, blood samples were collected 12 days into the study and at termination (day 27). After 12 days of exposure to 100 and 500μgL(-1) tebuconazole, plasma levels of testosterone (T) and dihydrotestosterone (DHT) were increased, while plasma 17β-estradiol (E2) concentrations were greatly reduced. Exposure to 0.1μgL(-1), on the other hand, resulted in decreased levels of T and DHT, with no effects observed for E2. After 27 days of exposure, effects were no longer observed in circulating androgen levels while the suppressive effect on E2 persisted in the two high-exposure groups (100 and 500μgL(-1)). Furthermore, tebuconazole increased gonadal concentrations of T and DHT as well as expression of the enzyme CYP17 (500μgL(-1), 27 days). These results suggest that tebuconazole exposure may supress the action of CYP17 at the lowest exposure (0.1μgL(-1)), while CYP19 suppression dominates at higher exposure concentrations (increased androgens and decreased E2). Increased androgen levels in plasma half-way into the study and in gonads at termination may thus be explained by compensatory mechanisms, mediated through increased enzymatic expression, as prolonged exposure had no effect on circulating androgen levels.
进行了一项为期27天的成年雄性非洲爪蟾（非洲爪蟾）对照暴露研究，以研究戊唑醇可能破坏类固醇生成的机制。通过液相色谱-串联质谱法（LC-MS/MS）在养殖水箱水中和目标组织（脂肪、肾脏、肝脏和大脑）中测定了这种杀菌剂，并且我们观察到生物浓缩具有组织特异性，生物浓缩因子（BCF）高达238。使用LC-MS/MS在性腺中以及使用气相色谱-串联质谱法（GC-MS/MS）在血浆中对多达10种不同的类固醇激素进行了定量，并进行了放射免疫测定以进一步测量雄激素。为了评估效应是否随暴露增加或动物是否适应了这种外源性物质，在研究的第12天和结束时（第27天）采集了血样。在暴露于100和500μg/L戊唑醇12天后，血浆睾酮（T）和二氢睾酮（DHT）水平升高，而血浆17β-雌二醇（E2）浓度大幅降低。另一方面，暴露于0.1μg/L导致T和DHT水平降低，未观察到对E2有影响。暴露27天后，循环雄激素水平不再观察到影响，而在两个高暴露组（100和500μg/L）中对E2的抑制作用仍然存在。此外，戊唑醇增加了性腺中T和DHT的浓度以及细胞色素P450 17α酶（CYP17）的表达（500μg/L，27天）。这些结果表明，在最低暴露水平（0.1μg/L）下，戊唑醇暴露可能抑制CYP17的作用，而在较高暴露浓度下，细胞色素P450 19酶（CYP19）抑制起主导作用（雄激素增加和E2减少）。因此，研究进行到一半时血浆中雄激素水平升高以及结束时性腺中雄激素水平升高可能是由补偿机制解释的，这种补偿机制是通过增加酶表达介导的，因为长时间暴露对循环雄激素水平没有影响。
