Meyn R E, vanAnkeren S C, Jenkins W T
Radiat Res. 1987 Mar;109(3):419-29.
The induction of single-strand breaks (SSBs) in the DNA of Chinese hamster ovary cells by X rays under different irradiation conditions was measured by the alkaline elution technique. The oxygen enhancement ratio (OER) for SSB induction determined for cells irradiated in air versus irradiation of cells made hypoxic by metabolic depletion of O2 was 9.7. However, when proteinase K was included in the cell lysis solution the OER was reduced to 4.2. The proteinase affected the elution rate only of the cells irradiated under hypoxic conditions, suggesting that DNA-protein crosslinks (DPCs) are preferentially produced in hypoxic cells by radiation. The ability to repair these DPCs was compared in two cell lines: the wild-type AA8 line and an excision-repair-deficient mutant line, UV-41. The AA8 line removed about 80% of the DPCs induced by radiation under hypoxic conditions within a 24-h repair incubation. The UV-41 line, on the other hand, removed only about 20% of the DPCs in the same time. The OERs for cell survival of these two lines are 3.1 for AA8 but only 1.9 for UV-41, suggesting that the DPCs preferentially induced in the DNA of cells irradiated under hypoxic conditions may contribute to cell killing when the normal DNA-repair mechanisms are compromised.
采用碱性洗脱技术测定了在不同照射条件下X射线对中国仓鼠卵巢细胞DNA中单链断裂（SSB）的诱导情况。在空气中照射细胞与通过代谢耗尽氧气使细胞处于低氧状态下照射细胞相比，测定的SSB诱导的氧增强比（OER）为9.7。然而，当细胞裂解液中加入蛋白酶K时，OER降至4.2。蛋白酶仅影响低氧条件下照射细胞的洗脱速率，这表明辐射优先在低氧细胞中产生DNA-蛋白质交联（DPC）。在两种细胞系中比较了修复这些DPC的能力：野生型AA8系和切除修复缺陷突变系UV-41。在24小时的修复孵育期内，AA8系去除了低氧条件下辐射诱导的约80%的DPC。另一方面，UV-41系在相同时间内仅去除了约20%的DPC。这两个细胞系细胞存活的OER，AA8为3.1，而UV-41仅为1.9，这表明在低氧条件下照射的细胞DNA中优先诱导的DPC，当正常的DNA修复机制受损时可能导致细胞死亡。
