电离辐射引起的DNA链断裂损伤及其修复

DNA链断裂是电离辐射的主要生物学效应之一,单链断裂由一次击中造成,所以与辐射剂量成线性关系,双链断裂可以一次击中造成,也可由两个位置相关的单链断裂迭加而成,所以与辐射剂量成线性——平方关系。已有各种理化方法能测定活细胞内的单链断裂和双链断裂数。细胞具有修复DNA链断裂的能力,但其机制远不如切除修复机制那么清楚。未修复的链断裂是致死的,被修复的单链断裂完全恢复DNA的正常结构与功能,被修复的双链断裂的生物学效应如何还不清楚。剂量率对辐射的生物学效应有重要影响。

IONIZING RADIATION-INDUCED DNA STRNAD BREAKS AND THEIR REPAIR

DNA strand breaks are the main biological effect of ionizing radia-tion. Single strand break is induced by a sinsle hit of irradiation and thus has lineardose response curve. Double strand break can be formed not only by a single hit, butalso by the overlap of two close single strand breaks located in the complemental stra-nds. The dose response curve of double strand breaks is linear -quadratic. DNA strandbreaks can be detected quantatively by various physicochemical methods. Cells are ableto repair both sinsle and double strand breaks. The mechanisms of repair, however,are not so clear as those of other repair models, excision repair, for example. The un-repaired strand breaks are lethal. Single strand repair is error-free. The biological ef-fects of repaied double strand kreaks remain unclear thus far. Dose rate has playsimportant role on the biological effects of ionizing radiations.