Dantzig A H, Fairgrieve M, Slayman C W, Adelberg E A
Somat Cell Mol Genet. 1984 Mar;10(2):113-21. doi: 10.1007/BF01534900.
A mutant of Chinese hamster ovary cells, CHY-2, was isolated on the basis of its reduced ability to grow on a limiting concentration of leucine and was found to be defective in uptake of leucine via the sodium-independent L system. Consistent with published reports that the L system can mediate melphalan uptake, the D10 of the mutant for melphalan was increased threefold under conditions designed to limit drug uptake to the L system (brief exposure in sodium-free medium). Unlike a previously described melphalan-resistant CHO mutant (CHr), CHY-2 displays no cross-resistance to colchicine or puromycin. It differs from a second melphalan-resistant CHO mutant, melr, in its sensitivity to melphalan in the presence of high Na+, and from a melphalan-resistant mouse leukemic cell in possessing normal levels of intracellular glutathione. Thus, CHY-2 represents a new melphalan-resistant mutant class. The effect of the CHY-2 mutation is pleiotropic, involving significant reductions in amino acid uptake via the L, A and Ly+ (but not ASC) systems. The primary defect is unknown; however, the mutant possesses normal intracellular concentrations of Na+ and K+ and normal membrane fluidity. The growth rate of the mutant in standard medium is greatly reduced (generation time of 60 h vs. 24 h), although it can be improved by the addition of a supplement containing high concentrations of leucine, proline, and peptides.
通过中国仓鼠卵巢细胞（CHY-2）在亮氨酸浓度受限的情况下生长能力降低这一特性，分离出了一种突变体，发现其通过不依赖钠的L系统摄取亮氨酸存在缺陷。与已发表的报告一致，即L系统可介导美法仑摄取，在旨在将药物摄取限制在L系统的条件下（在无钠培养基中短暂暴露），该突变体对美法仑的D10增加了三倍。与先前描述的对美法仑耐药的中国仓鼠卵巢细胞突变体（CHr）不同，CHY-2对秋水仙碱或嘌呤霉素无交叉耐药性。在高钠存在的情况下，它对美法仑的敏感性与另一种对美法仑耐药的中国仓鼠卵巢细胞突变体melr不同，并且与一种对美法仑耐药的小鼠白血病细胞不同，其细胞内谷胱甘肽水平正常。因此，CHY-2代表了一种新的对美法仑耐药的突变体类型。CHY-2突变的影响是多效性的，涉及通过L、A和Ly+（但不包括ASC）系统摄取氨基酸的显著减少。主要缺陷尚不清楚；然而，该突变体的细胞内钠和钾浓度正常，膜流动性也正常。尽管添加含有高浓度亮氨酸、脯氨酸和肽的补充剂可以提高其生长速度，但该突变体在标准培养基中的生长速度大大降低（代时为60小时，而正常为24小时）。
