Chao C C, Lund L G, Zinn K R, Aust A E
Department of Chemistry and Biochemistry, Utah State University, Logan 84322-0300.
Arch Biochem Biophys. 1994 Nov 1;314(2):384-91. doi: 10.1006/abbi.1994.1457.
Neutron-activated crocidolite, containing 55Fe and 59Fe, was used to determine whether iron was mobilized from crocidolite phagocytized by cultured human lung carcinoma cells (A549 cells). Cells were treated with neutron-activated crocidolite in medium at pH 6.8 or 7.4 for 24 h. The mobilization of iron into two subcellular fractions, 10,000g supernatant (total iron) or < 10,000 MW [low-molecular-weight (LMW)] was monitored using scintillation counting. Iron was mobilized from crocidolite at a rate similar to that observed in vitro when citrate was incubated with crocidolite for 24 h at pH 7.4, but the amount mobilized was greater when cells were cultured at pH 6.8 than at 7.4. Iron mobilization was not due to the medium nor did it appear to be due to differences in the amount of crocidolite phagocytized. At the highest concentration of crocidolite used for treatment at pH 7.4 (4.5 micrograms/cm2), a total of 3600 pmol iron/10(6) cells was mobilized of which 54 pmol/10(6) cells was in a LMW fraction. After estimation of the volume of the cells, this was calculated to be equivalent to an intracellular concentration of 1.4 mM iron of which 22 microM was in the LMW fraction. Cell survival decreased linearly as the iron mobilized into the LMW fraction increased, independent of the pH of the culture medium being used. These results suggest that iron mobilization from crocidolite into a LMW fraction may represent "iron overload" in cells which have phagocytized the fibers and may be responsible for crocidolite-dependent cytotoxicity and possibly other crocidolite-dependent biological effects.
含有55Fe和59Fe的中子活化青石棉被用于确定铁是否从被培养的人肺癌细胞（A549细胞）吞噬的青石棉中释放出来。细胞在pH 6.8或7.4的培养基中用中子活化青石棉处理24小时。使用闪烁计数法监测铁向两个亚细胞组分的释放情况，这两个亚细胞组分分别是10,000g上清液（总铁）或分子量小于10,000 [低分子量（LMW）]的组分。当柠檬酸盐在pH 7.4下与青石棉孵育24小时时，铁从青石棉中的释放速率与体外观察到的速率相似，但当细胞在pH 6.8下培养时，释放的铁量比在pH 7.4下培养时更多。铁的释放不是由于培养基，也似乎不是由于吞噬的青石棉量的差异。在pH 7.4下用于处理的最高青石棉浓度（4.5微克/平方厘米）时，总共释放了3600皮摩尔铁/10(6)个细胞，其中54皮摩尔/10(6)个细胞存在于LMW组分中。在估计细胞体积后，计算得出这相当于细胞内铁浓度为1.4毫摩尔，其中22微摩尔存在于LMW组分中。随着释放到LMW组分中的铁增加，细胞存活率呈线性下降，与所使用的培养基pH无关。这些结果表明，铁从青石棉释放到LMW组分中可能代表吞噬了纤维的细胞中的“铁过载”，并且可能是青石棉依赖性细胞毒性以及可能的其他青石棉依赖性生物学效应的原因。
