镉对中华蟾蜍蝌蚪生长、变态和Dios、TRs表达以及肝脏的影响

Effects of Cadmium on Growth,Metamorphosis and Dios,TRs Expression,Liver Health of Bufo gargarizans Larvae

镉(cadmium,Cd)是一种典型的工业毒素和环境污染物,对两栖类生物具有强烈的毒性作用。为了探讨镉对两栖类生物的毒害作用,选择中华蟾蜍蝌蚪作为受试生物,研究了不同浓度Cd对中华蟾蜍蝌蚪生长、变态和Dios、TRs表达以及肝脏的的影响,结果表明,500μg·L^(^(-1))Cd可以极显著降低蝌蚪的变态率、全长、尾长和体重(P<0.01);Real-time PCR结果显示,在变态高峰期,500μg·L^(^(-1))Cd可以显著下调Dio2、TRα和TRβ mRNA的相对表达量(P<0.05),显著上调Dio3 mRNA的相对表达量(P<0.05);透射电镜试验结果显示Cd可以破坏中华蟾蜍蝌蚪肝脏细胞胞浆中的细胞器和胆管中的微绒毛。综合以上结果,可知,高浓度的Cd可以紊乱甲状腺的内分泌和导致肝脏的病变,进而影响中华蟾蜍蝌蚪的生长和变态。

In the amphibian Bufo gargarizans, thyroid hormone played an important role in tadpole growth and metamorphosis. In this study, we examined the chronic toxic effects of cadmium on growth, metamorphosis and liver health of Bufo gargarizans larvae by using morphometric method and histological techniques. Moreover, we analyzed the expression of iodothyronine deiodinase （Dios） and thyroid hormone receptors （TRs） in Bufo gargarizans tadpoles at different cadmium treatments by real time PCR analysis. The significant reduction in metamorphosis percentage, total length, tail length and body mass were observed at 500 μg·L^-1 cadmium treatments （P〈0.01）. Histological examinations revealed that cadmium caused the damages in hepatocytes cytoplasmic organelles and microvilli of bile ducts. Furthermore, real-time PCR analysis suggested that the larvae exposed to 500 μg·L^-1 cadmium exhibited a greater decrease in Dio2, TRα and TRβ mRNA levels, whereas significant up-regulation of Dio3 mRNA levels were detected at 500 μg·L^-1 cadmium treatments （P〈0.05）. Our study indicated high concentration cadmium may disrupt thyroid hormone of Bufo gargarizans larvae.