Wang Chao, Liang Gang, Chai Lihong, Wang Hongyuan
College of Life Science, Shaanxi Normal University, Xi'an 710119, China.
School of Environmental Science and Engineering, Chang'an University, Xi'an 710054, China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Xi'an 710062, China.
Aquat Toxicol. 2016 Jan;170:24-30. doi: 10.1016/j.aquatox.2015.10.023. Epub 2015 Nov 5.
Chinese toad (Bufo gargarizans) tadpoles were exposed to copper (1, 6.4, 32 and 64μgL(-1) copper) from the beginning of larval period through completion of metamorphosis. We examined the effects of chronic copper exposure on mortality, growth, time to metamorphosis, tail resorption time, body size at the metamorphic climax (Gs 42) and completion of metamorphosis (Gs 46) and thyroid gland histology. In addition, type 2 and 3 iodothyronine deiodinase (Dio2 and Dio3), thyroid hormone receptors (TRα and TRβ) mRNA levels were also measured to assess disruption of TH synthesis. Our result showed that 6.4-64μgL(-1) copper concentration increased the mortality and inhibited the growth of B. gargarizans tadpoles. In addition, significant reduction in size at Gs 42 and a time delay to Gs 42 were observed at 6.4-64μgL(-1) copper treatments. Moreover, histological examinations have clearly revealed that 64μgL(-1) copper caused follicular cell hyperplasia in thyroid gland. According to real-time PCR results, exposure to 32 and 64μgL(-1) copper significantly up-regulated mRNA expression of Dio3, but down-regulated mRNA expression of TRα and TRβ mRNA level. We concluded that copper delayed amphibian metamorphosis through changing mRNA expression of Dio3, TRα and TRβ, which suggests that copper might have the endocrine-disrupting effect.
从幼体期开始直至变态完成，中华蟾蜍蝌蚪暴露于铜（1、6.4、32和64μg L⁻¹铜）环境中。我们研究了长期铜暴露对死亡率、生长、变态时间、尾部吸收时间、变态高峰期（Gs 42）和变态完成时（Gs 46）的体型以及甲状腺组织学的影响。此外，还测量了2型和3型碘甲状腺原氨酸脱碘酶（Dio2和Dio3）、甲状腺激素受体（TRα和TRβ）的mRNA水平，以评估甲状腺激素合成的干扰情况。我们的结果表明，6.4 - 64μg L⁻¹的铜浓度会增加中华蟾蜍蝌蚪的死亡率并抑制其生长。此外，在6.4 - 64μg L⁻¹铜处理组中，观察到Gs 42时体型显著减小以及达到Gs 42的时间延迟。而且，组织学检查清楚地显示，64μg L⁻¹的铜会导致甲状腺滤泡细胞增生。根据实时PCR结果，暴露于32和64μg L⁻¹铜会显著上调Dio3的mRNA表达，但下调TRα和TRβ mRNA水平。我们得出结论，铜通过改变Dio3、TRα和TRβ的mRNA表达来延迟两栖动物的变态，这表明铜可能具有内分泌干扰作用。
