Bertolero F, Pozzi G, Sabbioni E, Saffiotti U
Carcinogenesis. 1987 Jun;8(6):803-8. doi: 10.1093/carcin/8.6.803.
Cytotoxicity, morphological neoplastic transformation, cellular uptake and metabolic reduction were determined in BALB/3T3 Cl A31-1-1 cells for trivalent arsenic (sodium arsenite, As3+) and for pentavalent arsenic (sodium arsenate, As5+). The levels of cellular uptake of 73As-labelled sodium arsenite and arsenate were dose-dependent and highest in the first hour. At equimolar concentration (3 X 10(-6) M), cellular uptake was 4-fold higher for As3+ than for As5+. Cytotoxicity was higher for As3+ than for As5+, but when correlated to total As cell burden it showed no significant difference for the two forms. Morphological transformation focus assays showed transforming activity for both As3+ and As5+, with relative transformation frequencies also of approximately 4:1. Recovery from the cytosol after exposure for 1-24 h was greater than 90% for either form of absorbed As. Exposure to As3+ yielded 100% as As3+ in cytosol, but exposure to As5+ yielded greater than 70% as As3+, showing a high rate of intracellular metabolic reduction. No methylated metabolites were detected by ion-exchange chromatography. After 24-h incubation in cell-free medium, oxidation of As3+ to As5+ occurred up to 30% of the dose, but incubation in the presence of cells lowered the oxidation level to 4%. As5+ was recovered unchanged from cell-free medium (24-h incubation), but in the presence of the cells it yielded up to 5% as As3+ within 24 h and the cumulative release of As3+ by cells exposed to As5+ was dose-dependent. Glutathione depletion by diethylmaleate inhibited reduction of As5+ to As3+ by these cells up to 25% of controls, showing that As5+ reduction is partly dependent on glutathione. These results suggest that As3+ is the form responsible for the cytotoxic and transforming effects, independently of the valence state of the inorganic arsenic in the culture medium.
在BALB/3T3 Cl A31-1-1细胞中测定了三价砷（亚砷酸钠，As3+）和五价砷（砷酸钠，As5+）的细胞毒性、形态学肿瘤转化、细胞摄取和代谢还原情况。73As标记的亚砷酸钠和砷酸钠的细胞摄取水平呈剂量依赖性，且在最初1小时内最高。在等摩尔浓度（3×10(-6) M）下，As3+的细胞摄取量比As5+高4倍。As3+的细胞毒性高于As5+，但与细胞内总砷含量相关时，两种形式的细胞毒性无显著差异。形态学转化集落试验表明As3+和As5+均具有转化活性，相对转化频率也约为4:1。暴露1 - 24小时后，两种形式的吸收砷从细胞溶质中的回收率均大于90%。暴露于As3+时，细胞溶质中As3+的含量为100%，但暴露于As5+时，细胞溶质中As3+的含量大于70%，表明细胞内代谢还原率较高。离子交换色谱未检测到甲基化代谢产物。在无细胞培养基中孵育24小时后，As3+氧化为As5+的量可达剂量的30%，但在有细胞存在的情况下孵育，氧化水平降至4%。As5+在无细胞培养基中（24小时孵育）回收时未发生变化，但在有细胞存在的情况下，24小时内可产生高达5%的As3+，且暴露于As5+的细胞中As3+的累积释放量呈剂量依赖性。马来酸二乙酯导致的谷胱甘肽耗竭可使这些细胞将As5+还原为As3+的能力抑制至对照的25%，表明As5+的还原部分依赖于谷胱甘肽。这些结果表明，As3+是造成细胞毒性和转化作用的形式，与培养基中无机砷的价态无关。
