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目的对不同酸度条件下金属硫蛋白结合镉离子和锌离子的含量进行测定,并对不同酸度下锌、镉金属离子含量比值的分析为动植物镉中毒的解毒条件提供依据。方法采用金属-血红蛋白饱和法除去过量金属离子,然后用ICP-MS测得金属硫蛋白与锌、镉的结合量。结果实验测定的所有pH值的锌、镉的RSD均在5%之内,方法的回收率在80.17%～115.6%之间,说明此方法是可靠的。结论由于组成金属硫蛋白的α-、β-结构域的差异,pH3.6时结合在β-结构域的锌发生解离,结合在α-结构域的锌部分解离,这时溶液中存在大量的游离锌离子,锌含量增加。在锌-金属硫蛋白中加入镉,锌、镉含量在pH为3.6～8.6范围内基本上呈现相反的趋势。表明小剂量的Zn预处理能减轻Cd的急性毒性,Zn对Cd的肝肾毒性有明显拮抗作用。同时比较不同pH值的Cd/Zn值发现pH=6.6时Cd/Zn值最大,pH=8.6时Cd/Zn值最小,推测偏碱性时添加小剂量的Zn对减小镉的毒性比较有利。
OBJECTIVE To determine the content of metallothionein bound cadmium (I) and zinc (I) in different acidity conditions, and to analyze the ratio of metal ions of zinc and cadmium at different acidity to provide basis for the detoxification of animal and plant cadmium poisoning. Methods The metal-hemoglobin saturation method was used to remove excess metal ions, and then the amount of metallothionein bound to zinc and cadmium was measured by ICP-MS. Results The RSDs of zinc and cadmium were all within 5% at all pH values tested. The recoveries of the methods were between 80.17% and 115.6%, indicating that this method is reliable. Conclusions Due to the differences in the α- and β-domains of the constituent metallothioneins, the binding of zinc in the β-domain at pH 3.6 disassociates and the zinc moiety that is bound to the α-domain dissociates, at which point the solution is present A lot of free zinc ions, zinc content increased. The content of cadmium, zinc and cadmium in zinc-metallothionein basically showed the opposite trend in the range of pH 3.6 ~ 8.6. The results showed that low dose of Zn pretreatment can reduce the acute toxicity of Cd, and Zn can obviously antagonize the hepatotoxicity of Cd. At the same time, it was found that the Cd / Zn value was the highest when the pH value was 6.6 and the lowest was Cd / Zn value when the pH value was 8.6. It is better to add a small dose of Zn to reduce the toxicity of cadmium when the pH value is 8.6.