Pinedo H M, Zaharko D S, Bull J M, Chabner B A
Cancer Res. 1976 Dec;36(12):4418-24.
The cytotoxic effect of methotrexate (MTX) for mouse bone marrow cells has been studied by in vitro of the granulocyte precursor cell (CFU-C) in a medium containing dialyzed fetal calf serum and dialyzed L-cell supernatant. The formation of 50-cell colonies was inhibited to 50% of control by 10(-8) M MTX. Further increases in MTX concentration rapidly abolished colony formation by CFU-C. The potential of leucovorin and nucleosides to rescue the CFU-C from MTX toxicity was studied. Toxicity of 10(-7) M MTX was completely reversed by equimolar concentrations of leucovorin, but with higher MTX concentrations, relatively more leucovorin was required. While 10(-5) M MTX was rescued by 10(-3) M leucovorin, rescue of the toxic effect of 10(-4) M MTX by 10(-3) M leucovorin was not observed. In contrast to the rescue by Leucovorin, toxicity of all MTX concentrations up to 10(-4) M was completely prevented by 10(-5) M thymidine with 10(-5) M adenosine, inosine, or hypoxanthine. Single nucleosides or thymidine with guanosine were ineffective, as were lower concentrations (less than or equal to 10(-6)M) of the effective combinations. Thus, while leucovorin reversed the MTX toxicity to CFU-C competitively, rescue by nucleosides was noncompetitive. The significance and possible usefulness of these findings for chemotherapeutic protocols are discussed.
在含有透析胎牛血清和透析L细胞上清液的培养基中，通过体外培养粒细胞前体细胞（CFU-C），研究了甲氨蝶呤（MTX）对小鼠骨髓细胞的细胞毒性作用。10^(-8)M MTX可将50细胞集落的形成抑制至对照的50%。MTX浓度进一步升高会迅速消除CFU-C的集落形成。研究了亚叶酸钙和核苷将CFU-C从MTX毒性中解救出来的潜力。等摩尔浓度的亚叶酸钙可完全逆转10^(-7)M MTX的毒性，但MTX浓度更高时，需要相对更多的亚叶酸钙。虽然10^(-5)M MTX可被10^(-3)M亚叶酸钙解救，但未观察到10^(-3)M亚叶酸钙对10^(-4)M MTX毒性的解救作用。与亚叶酸钙的解救作用相反，10^(-5)M胸苷与10^(-5)M腺苷、肌苷或次黄嘌呤可完全预防高达10^(-4)M的所有MTX浓度的毒性。单核苷或胸苷与鸟苷无效，有效组合的较低浓度（小于或等于10^(-6)M）也无效。因此，虽然亚叶酸钙竞争性地逆转了MTX对CFU-C的毒性，但核苷的解救作用是非竞争性的。讨论了这些发现对化疗方案的意义和可能的用途。
