Fox J C, McNally N J
Cancer Research Campaign Gray Laboratory, Mount Vernon Hospital, Middlesex, U.K.
Int J Radiat Biol. 1988 Dec;54(6):1021-30. doi: 10.1080/09553008814552401.
We have investigated the effects of 250kVp X-rays and 2.3 MeV (mean energy) neutrons on the cell survival, DNA double-strand break (dsb) induction and repair (using the Kohn neutral elution technique) in V79 cells. The lethal effects of neutrons were shown to be significantly greater than for a similar dose of X-rays (RBE = 3.55 at 10 per cent survival). However, the RBE for dsb induction, in a dose range of 10-50 Gy, was 1. On investigating the repair of DNA dsb induced by either X-ray or neutron irradiation, clear differences in the pattern of repair were found. Both a fast and a slow component of repair were seen in both cases; the former, however, was reduced following neutron irradiation and, since the amount of slow repair was similar in both cases, this resulted in proportionally more unrejoined breaks after neutrons. These experiments were carried out with elution buffer at pH 9.6; however, when similar experiments were performed at pH 7.2 the results obtained support our earlier findings. We suggest that these differences in DNA dsb repair reflect basic differences in the nature of the lesions induced by high- and low-LET ionizing radiations.
我们研究了250kVp X射线和2.3 MeV（平均能量）中子对V79细胞的细胞存活、DNA双链断裂（dsb）诱导及修复（采用科恩中性洗脱技术）的影响。结果显示，中子的致死效应显著大于相同剂量的X射线（在10%存活率时，相对生物效应RBE = 3.55）。然而，在10 - 50 Gy剂量范围内，dsb诱导的RBE为1。在研究X射线或中子辐照诱导的DNA dsb修复时，发现修复模式存在明显差异。两种情况下均观察到快速和慢速修复成分；不过，中子辐照后快速修复成分减少，且由于两种情况下慢速修复量相似，这导致中子辐照后未连接的断裂比例更高。这些实验是在pH 9.6的洗脱缓冲液中进行的；然而，当在pH 7.2进行类似实验时，所得结果支持我们早期的发现。我们认为，DNA dsb修复的这些差异反映了高传能线密度和低传能线密度电离辐射诱导损伤性质的根本差异。
