Evidence of hemoglobin binding to arsenic as a basis for the accumulation of arsenic in rat blood
Evidence of hemoglobin binding to arsenic as a basis for the accumulation of arsenic in rat blood
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DOI：
10.1021/tx049756s
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发表时间：
2004-12-01
影响因子：
4.1
通讯作者：
Le, XC
中科院分区：
文献类型：
--
作者：
Lu, ML;Wang, HL;Le, XC
四种三价砷物质，无机亚砷酸盐（iAs（III）），单甲基亚胂酸（MMA（III）），二甲基亚胂酸（DMA（III）），氧化苯胂（PhAsO）-O-III），已显示出与大鼠和人类血红蛋白（Hb）的结合亲和力增加。结合化学计量与Hb的α和β链中反应性半胱氨酸残基的数量一致。比较大鼠血红蛋白和人血红蛋白对同一种三价砷的结合亲和力，大鼠血红蛋白的表观结合常数是人血红蛋白的3-16倍。比较实验涉及人类和大鼠红细胞（RBC）与iAs（III），MMA（III）和DMA（III）的孵育表明，15-30倍以上的砷物种结合到大鼠RBC的血红蛋白比人RBC。用含砷饲料喂养的大鼠进行的体内实验表明，大鼠红细胞中的砷主要以蛋白结合形式存在。通过纳米电喷雾质谱法对这些大鼠RBC中的砷物质进行进一步表征，证实大多数砷与Hb的α链结合。两者合计，这些结果表明，较强的结合亲和力，这些砷物种的大鼠血红蛋白是负责砷在大鼠血液中的积累。结果提供了一个化学基础来解释先前观察到的有趣的差异，在保留砷在人类和大鼠。所描述的技术和方法可应用于砷与其他功能蛋白质相互作用的研究。
Four trivalent arsenic species, inorganic arsenite (iAs(III)), monomethylarsonous acid (MMA(III)), dimethylarsinous acid (DMA(III)), and phenylarsine oxide ((PhAsO)-O-III), have shown increasing binding affinity with the hemoglobin (Hb) of rats and humans. The binding stoichiometry was consistent with the number of reactive cysteine residues in the alpha and beta chains of Hb. Comparing the binding affinity of rat Hb and human Hb for the same trivalent arsenic species, rat Hb was 3-16 times stronger than human Hb as demonstrated by their apparent binding constants. Comparative experiments involving incubation of human and rat red blood cells (RBC) with iAs(III), MMA(III), and DMA(III) showed that 15-30-fold more arsenic species were bound to the Hb of rat RBC than that of human RBC. In vivo experiments using rats fed with an arsenic-supplemented diet showed that arsenic in RBC of the rats was predominantly found in the protein-bound form. Further characterization by nanoelectrospray mass spectrometry of the arsenic species in the RBC of these rats confirmed that most arsenic was bound to the alpha chain of Hb. Taken together, these results suggest that the stronger binding affinity of these arsenic species to rat Hb is responsible for the accumulation of arsenic in rat blood. The results provide a chemical basis to explain the previously observed intriguing difference in the retention of arsenic in the human and the rat. The techniques and approaches described can be applied to the studies of arsenic interactions with other functional proteins.