Determination of trivalent methylated arsenicals in biological matrices
Determination of trivalent methylated arsenicals in biological matrices
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DOI：
10.1006/taap.2001.9226
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发表时间：
2001-08-01
影响因子：
3.8
通讯作者：
Thomas, DJ
中科院分区：
文献类型：
--
作者：
Del Razo, LM;Styblo, M;Thomas, DJ
酶催化氧化甲基化砷产生甲基化砷，含有五价砷（As-V）。由于三价砷（As-III）是这种甲基转移酶的有利底物，含有As-V的甲基化砷在细胞中被还原为三价。含有As-III的甲基化砷是NADPH依赖性黄素蛋白氧化还原酶和许多细胞类型中的强效细胞毒素的极强效抑制剂。因此，含有As-III的甲基化砷化物的形成可以被适当地视为活化步骤，而不是解毒的手段。认识到甲基化砷的毒性和代谢的As-III的作用，强调需要分析方法来检测和量化这些物种的生物样品。因此，开发了一种方法，利用pH值依赖的差异，从无机和甲基化的砷，含有砷-V或砷-III的胂代。还原与硼氢化物在pH值6产生砷化氢从无机砷-III，甲基砷-III，和二甲基砷-III，但不是从无机砷-V，甲基砷-V，和二甲基砷-V。还原与硼氢化物在pH值2或更低产生砷化氢从砷，包含无论是砷-V或砷-III。砷化氢被收集在液氮冷却的气相色谱收集器中，随后加热收集器，使砷化氢通过其沸点分离。采用原子吸收分光光度法对砷化物进行检测和定量。无机As-III、甲基As-III和二甲基As-III的检测限（ng As ml（-1））分别为1.1、1.2和6.5。该方法已用于水、人尿和培养细胞中砷的分析。均为甲基As-III。和二甲基As-III检测尿液样本从个人谁长期消费无机砷污染的水和人体细胞在体外暴露于无机As-III。无机砷和甲基化砷的可靠定量分析。在生物样品中的生物标记物将有助于这些物种的毒性研究，并可能提供一个新的生物标志物的影响，慢性暴露于砷。(C)北京：科学出版社.
The enzymatically catalyzed oxidative methylation of As yields methylated arsenicals that contain pentavalent As (As-V). Because trivalent As (As-III) is the favored substrate for this methyltransferase, methylated arsenicals containing As-V are reduced to trivalency in cells. Methylated arsenicals that contain As-III are extremely potent inhibitors of NADPH-dependent flavoprotein oxidoreductases and potent cytotoxins in many cell types. Therefore, the formation of methylated arsenicals that contain As-III may be properly regarded as an activation step, rather than a means of detoxification. Recognition of the role of methylated arsenicals that contain As-III in the toxicity and metabolism of As emphasizes the need for analytical methods to detect and quantify these species in biological samples. Hence, a method was developed to exploit pH-dependent differences in the generation of arsines from inorganic and methylated arsenicals that contain either As-V or As-III. Reduction with borohydride at pH 6 generated arsines from inorganic As-III, methyl As-III, and dimethyl As-III, but not from inorganic As-V, methyl As-V, and dimethyl As-V. Reduction with borohydride at pH 2 or lower generated arsines from arsenicals that contained either As-V or As-III. Arsines are trapped in a liquid nitrogen-cooled gas chromatographic trap, which is subsequently warmed to allow separation of the hydrides by their boiling points. Atomic absorption spectrophotometry is used to detect and quantify the arsines. The detection limits (ng As ml(-1)) for inorganic As-III, methyl As-III, and dimethyl As-III are 1.1, 1.2, and 6.5, respectively. This method has been applied to the analysis of arsenicals in water, human urine, and cultured cells. Both methyl As-III. and dimethyl As-III are detected in urine samples from individuals who chronically consumed inorganic As-contaminated water and in human cells exposed in vitro to inorganic As-III. The reliable quantitation of inorganic and methylated arsenicals that contain As-III. in biological samples will aid the study of the toxicity of these species and may provide a new biomarker of the effects of chronic exposure to As. (C) 2001 Academic Press.