RADIATION-INDUCED LONG LIVED RADICALS CAUSING MUTATION AND TRANSFORMATION

许多辐射生物学领域的研究认为，活跃的短寿命自由基，如OH和H自由基，在表达辐射h细胞的基因效应，如突变和致癌方面发挥着重要作用。然而，我们用电子自旋共振波谱在室温下的金黄地鼠胚胎(GHE)细胞中发现了一种新的长寿命自由基(T_&lt；1/2&gt；20hr)。在突变诱导中，它可能比活跃的短寿命半径更重要。在照射后20分钟或6小时分别加入维生素C(MA)，细胞可清除LLR，同时对突变、转化等遗传毒性也有明显的抑制作用。由于活性氧物种(ROS)在照射后的微秒内消失，AsA不清除ROS，而是清除LLR。因此，我们提出LLR可能是诱发突变的重要自由基，并且可能对辐射后哺乳动物细胞的遗传毒性起重要作用。照射前或照射后细胞中加入AsA对减少细胞死亡和染色体畸变率没有任何作用。通过ESEEM光谱的研究，我们发现LLR可能位于水分子较少的生物聚合物内部。通过进一步分析LLR的ESR谱，并比较蛋白质和DNA中自由基的产率，我们得出结论：LLR是在蛋白质中产生的，并以氧化半胱氨酸基的形式被归类为亚磺基。LLR不是在DNA或脂类中产生的。我们的结果表明，蛋白质中产生的LLR是辐射细胞中基因突变的原因。虽然这与目前辐射生物学中的普遍观点相矛盾，但辐射生物学中的许多未解决的现象都可以很好地解释。

Many researches studying in area of radiation biology have been believed that active short life-time radicals such as OH and H radicals, play an important role to express genoto do effects of radiation h cells, such as mutation and cancer induction. However, we found a new type of radicals with long life-time (T_<1/2>20hr) in gamma ray hmdiated golden hamster embryo (GHE) cells at room temperature by using ESR spectroscopy. It may be more important in mutation induction than the active short live radials. When Vitamin C (MA) is added to the gamma-or X-irradiated cells at 20 min or 6 hr after the irradiation, respectively, LLR are scavenged by them simuhaneousty with the drastic suppression of genotoxicity such as mutation and transformation. Since reactive oxygen species (ROS) disappear within microsecond after the irradiation, AsA do not scavenge the ROS but LLR. Therefore, we have proposed that LLR must be responsible radicals for inducing mutation, and probably important for the genotoxicity in the irradiated mammalian cells. Addition of AsA to the cells before or after irradiation does not have any effects on reducing cell death and chromosomal aberration. By the studies using ESEEM spectroscopy, we found that LLR probably locate in interior of biopolymers where few water molecules exist. By further analysis of the ESR spectra of LLR and comparison of the yields of radicals in proteins and DNA, we reached to the conclusion that LLR are produced in protein and assigned as sulfinyl radicals as oxidized cysteine groups. LLR are not produced in DNA or in lipids. Our result show that the LLR produced in protein is responsible for the gene mutation in irradiated cells. Although this contradicts now common view in the radiation biology, many unresolved phenomena in the radiation biology can be explained well.