INTERACTION OF CHROMIUM WITH MITOCHONDRIA

本研究项目的总体目标是了解 铬（VI）化合物作为致癌物的机制。 三 我们计划使用的解决这个问题的方法是：（1）线粒体 将被用作研究吸收减少机制的模型系统 建议用于铬（VI）致癌性，因为该细胞器含有 铬（VI）还原酶活性以及定义的DNA（mtDNA） （2）铬与重复DNA序列的结合， 由于核DNA作为靶可能不同，因此将确定核起源 对于来自线粒体DNA的铬化合物;和（3）致癌 铬（VI）化合物将与非致癌性铬（III）进行比较 铬化合物与线粒体DNA和重复DNA的结合， 为了区分与生物活性相关的相互作用， 铬化合物 我们计划测试的假设，还原活化铬（VI） 在确定的DNA序列上产生特异性的铬-DNA加合物， 因为它们的DNA结构而被优先攻击。 具体目标 （1）比较铬（VI）和铬（III） 与大鼠线粒体DNA形成铬络合物的能力， 体内和体外的重复DNA。 的形成和修复 线粒体DNA和重复DNA片段中的铬-DNA加合物将被 用51Cr标记的重铬酸钠处理后测定， 三氯化铬。 (2)测定铬的序列特异性 与线粒体和重复DNA的相互作用。 序列 铬-DNA加合物对mtDNA的特异性和碱不稳定性， 将使用DNA测序确定重复DNA片段 技术. (3)确定铬（VI）还原的机理， 线粒体NADH-泛醌氧化还原酶。 铬（VI）的代谢 通过复合物I和分离的组分将被确定。 的产生 反应性铬（V）和自由基物质， 铬（VI）通过这些系统将通过EPR光谱监测。 （四） 测定顺铂（II）结合大鼠线粒体和 体内和体外重复DNA;和（5）确定 铬对线粒体DNA复制和线粒体基因表达的影响。

The overall objective of this research project is to understand the mechanism by which chromium(VI) compounds act as carcinogens. The three approaches we plan to use in attacking this problem are: (1) mitochondria will be used as a model system for studying the uptake-reduction mechanism proposed for chromium(VI) carcinogenicity since this organelle contains chromium(VI) reductase activity as well as DNA (mt DNA) of defined sequence; (2) the binding of chromium to repetitive DNA sequences of nuclear origin will be determined since nuclear DNA may differ as a target for chromium compounds from mitochondrial DNA; and (3) carcinogenic chromium(VI) compounds will be compared with noncarcinogenic chromium(III) compounds with respect to chromium binding to mt DNA and repetitive DNA in order to distinguish interactions related to the biological activity of the chromium compounds. We plan to test the hypothesis that reductive activation of chromium(VI) results in specific chromium-DNA adducts at defined DNA sequences which are preferentially attacked because of their DNA structure. The specific aims of the proposed research are: (1) Compare chromium(VI) and chromium(III) for their ability to form chromium complexes with rat mitochondrial DNA and repetitive DNA in vivo and in tro. The formation and repair of chromium-DNA adducts in mt DNA and repetitive DNA fragments will be determined after treatment with 51Cr-labeled sodium dichromate and chromium(III) chloride. (2) Determine the sequence specificity of chromium interactions with mitochondrial and repetitive DNA. The sequence specificity and alkaline lability of the chromium-DNA adducts on mt DNA and repetitive DNA fragments will be determined using DNA sequencing techniques. (3) Determine the mechanism of chromium(VI) reduction by mitochondrial NADH-ubiquinone oxidoreductase. Metabolism of chromium(VI) by Complex I and isolated components will be determined. The generation of reactive chromium(V) and free radical species upon reduction of chromium(VI) by these systems will be monitored by EPR spectroscopy. (4) Determine the ability of cis-platinum(II) to bind to rat mitochondrial and repetitive DNA in vivo and in vitro; and (5) Determine the effect of chromium on the replication of mt DNA and on the expression of mt genes.