锌或铜诱导肝脏金属硫蛋白结合锌镉比值与铜镉比值的研究
Ratios of Zinc/Cadmium, Copper/Cadmium in Liver Metallothionein Induced by Zinc or Copper
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摘要:
目的 观察镉(Cd)染毒后锌(Zn)或铜(Cu)诱导肝脏金属硫蛋白(MT)结合锌镉比值(Zn/Cd)与铜镉比值(Cu/Cd)的关系及其意义。 方法 将28只雄性Wistar大鼠随机分为7组,每组4只,分别为:空白对照组(0),不做任何处理;非预处理组(A1、A2),皮下注射生理盐水;Zn处理组(B1、B2),皮下注射ZnCl2(每千克体重染Zn 25mg);Cu处理组(C1、C2),皮下注射CuSO4(每千克体重染Cu 12.5mg)。预处理24h后,为实验组动物皮下注射镉.金属硫蛋白(CdMT,Cdmetallothionein),造成Cd急性中毒,其中A1、B1、C1组每千克体重染Cd0.1mg,A2、B2、C2组每千克体重染Cd 0.4mg。24h后处死,取肝脏,制备匀浆。离心后取上清液,加入SephadexG-75色谱层析柱。 结果 空白对照组动物肝脏中与MT结合的最主要金属元素是Zn,而Cd、Cu含量在检测限以下;与前者相比,A1、A2组动物肝脏MT和Cd含量随染毒剂量增加而升高,且A1、A2组肝脏MT中Zn/Cd值分别为20.0和10.0;B1、B2组肝脏MT中Zn/Cd值分别为20.8和20.3,Cu离子未检出;C1、C2组肝脏MT的Cu/Cd值分别为80.0和36.5,Zn含量下降明显。 结论 不同剂量Cd染毒后,Zn或Cu诱导动物肝脏MT中金属含量比例存在差异,Cu/Cd值高于Zn/Cd值,即与MT结合的Cd相比,Cu更易取代与MT结合的Zn。另外,肝脏中非MT结合Zn也是影响与MT结合的金属离子稳态的重要因素。 Abstract:Objective To observe the ratios of Zn/Cd, Cu/Cd in liver metallothionein induced by zinc or copper, under exposure to Cd in rats. Methods Wistar male rats were divided into 7 groups, 4 animals for each group. Group 0 was left nontreated as blank control. Group A1 and A2 were subcutaneously injected with normal saline, Group B1 and B2 were injected with ZnCl2 in the dose of 25mg Zn/kg Body Mass and Group C1 and C2 with CuSO4 in the dose of 12.5 mg Cu/kg Body Mass. Twenty four hours after Zn or Cu pre-treatment, Group A1, B1 and C1 and Group A2, B2 and C2 were administered cadmium-metallothionein (CdMT) in the dose of 0.1 or 0.4mg Cd/kg Body Mass, respectively. After 24 hours of CdMT injection, liver was taken and homogenized. Cytosol gained after centrifugation(105 000 g)was applied to gel chromatography on Sephadex G-75. Results Among animals in Group 0, Zn was the dominant metallic element bound to MT in liver, but neither Cd nor Cu could be detected. In the non-pretreated group, there was a dose related increase of MT and Cd concentration, with 20.0 and 10.0 of Zn/Cd ratio for A1 and A2, respectively. The ratios of Zn/Cd in MT were 20.8 in Group B1 and 20.3 in Group B2, and Cu was below the detection limit for both. The ratios of Cu/Cd were 80.0 in Group C1 and 36.5 in Group C2, and however, the level of Zn decreased considerably. Conclusion The results showed in this in viro experiment that Zn bound to MT was more easily replaced by Cu than Cd bound to MT. The non-MT-bound Zn in liver tissues may be one of the explanations for the difference.
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