Bogdan G M, Sampayo-Reyes A, Aposhian H V
Department of Pharmacology and Toxicology, University of Arizona, Tucson 85721.
Toxicology. 1994 Nov 11;93(2-3):175-93. doi: 10.1016/0300-483x(94)90077-9.
It is well known that arsenite/arsenate (As3+/As5+) administered to rabbits is bound initially to cellular proteins of the liver before methylated arsenic metabolites appear in urine. This protein binding may decrease the in situ toxicity of inorganic arsenic by decreasing its metabolic availability until it is methylated enzymatically. We have investigated the binding of As3+ and As5+ to the cytosolic proteins of rabbit liver. The results indicate that when cytosolic proteins are incubated with inorganic arsenic, the amount of As3+ bound is 13 times greater than that for As5+. Arsenite-specific binding sites on cytosolic proteins were determined to be 67% of the total (specific and non-specific) number of possible binding sites. Ammonium sulfate fractionation, non-denaturing PAGE and gel filtration chromatography indicate that three liver proteins with molecular weights of 100 kDa, 450 kDa and > 2000 kDa strongly bind arsenite. The radioactive profiles after gel filtration chromatography of liver cytosolic proteins are very similar whether As3+ binding occurs in vitro or in vivo. Thus, the in vitro model appears to be valid for further study of these arsenite-binding proteins.
众所周知，给兔子施用亚砷酸盐/砷酸盐（As3+/As5+）后，在尿液中出现甲基化砷代谢物之前，它最初会与肝脏的细胞蛋白结合。这种蛋白结合可能会通过降低无机砷的代谢可用性来降低其原位毒性，直到它被酶甲基化。我们研究了As3+和As5+与兔肝脏胞质蛋白的结合。结果表明，当胞质蛋白与无机砷孵育时，结合的As3+量比As5+多13倍。胞质蛋白上的亚砷酸盐特异性结合位点占可能结合位点总数（特异性和非特异性）的67%。硫酸铵分级分离、非变性聚丙烯酰胺凝胶电泳和凝胶过滤色谱表明，三种分子量分别为100 kDa、450 kDa和>2000 kDa的肝脏蛋白强烈结合亚砷酸盐。无论As3+结合是在体外还是体内发生，肝脏胞质蛋白凝胶过滤色谱后的放射性图谱都非常相似。因此，体外模型似乎对进一步研究这些亚砷酸盐结合蛋白是有效的。
