镉诱导大鼠睾丸三种类型细胞和肝脏金属硫蛋白基因表达的研究

Cell-and time-dependent metallothionein gene expression in testes of rats treated with cadmium

目的 :啮齿类动物睾丸较肝脏对镉毒性更敏感。通过对镉诱导早期大鼠睾丸三种类型细胞 (支持细胞、间质细胞和生精细胞 )与肝脏金属硫蛋白 (MT)及其亚型 MT1、MT2表达的研究 ,阐明大鼠睾丸对镉毒性较肝脏更敏感的分子机制。方法 :采用半定量 RT- PCR、EL ISA、原子分光光度吸收法 ,观察镉处理后不同时相大鼠睾丸三种类型细胞与肝脏 MT基因表达的变化。结果 :睾丸组织中存在 MT。同时还发现 0 h对照组大鼠镉处理后肝脏 MT m RNA增加并保持较高的基础水平 ,3h达峰值后下降 ;而睾丸支持细胞和间质细胞则在 6 h达高峰。镉中毒大鼠睾丸支持细胞和肝脏 MT1m RNA的变化幅度要低于MT2 m RNA,而在间质细胞中则相反。此外 ,生精细胞 MT1m RNA在镉处理后 0～ 3h减少 ,然后增加 ,而 MT2 m RNA的变化则相反 ,而且它们的诱导变化幅度较其他细胞低。镉暴露后肝脏 MT m RNA和 MT均升高 ,但在睾丸三种类型细胞中 MT的表达并没有增加。 结论 :镉诱导后 MT m RNA的表达具有细胞和时间依赖性 ;镉虽然能诱导睾丸 MT m RNA的转录但没有促进其 MT的合成 。

Objective:To compare metallothionein( MT ) gene expression, MT protein accumulation, and cadmium(Cd) retention in freshly isolated testicular various cell types and liver of rats treated with Cd,providing information for the molecular mechnism of testes sensitivity to Cd. Methods: MT 1 and MT 2 mRNA levels were determined by semi quantitative RT PCR analysis followed by densitometry scanning, and MT was estimated by the enzyme linked immunosorbent assay (ELISA). Cd content was determined by atomic absorption spectrophotometry. Testicular lesions were not grossly or histologically observed in rats treated with 4.0 μmol/kg Cd. Results:Both MT mRNA and MT were constitutively present in testes and liver.Testis had higher levels of MT 1 and MT 2 mRNA in 1 h,3 h,6 h compared with control,but MT protein did not increase.Cd exposure also increased hepatic MT s mRNA and MT protein.Conclusion:These results indicate that although Cd exposure results in increase of MT mRNA in testis,it does not enhance MT synthesis,this may account for higher susceptibility of testes to Cd toxicity and carcinogenesis relative to liver.