Calini V, Urani C, Camatini M
Dipartimento di Scienze dell'Ambiente e del Territorio, Università degli Studi di Milano-Bicocca, Milan, Italy.
Cell Biol Toxicol. 2002;18(6):369-79. doi: 10.1023/a:1020811522100.
Ionizing radiation is a potent inducer of DNA damage because it causes single- and double-strand breaks, alkali-labile sites, base damage, and crosslinks. The interest in ionizing radiation is due to its environmental and clinical implications. Single-strand breaks, which are the initial damage induced by a genotoxic agent, can be used as a biomarker of exposure, whereas the more biologically relevant double-strand breaks can be analyzed to quantify the extent of damage. In the present study the effects of 137CS gamma-radiation at doses of 1, 5, and 10 Gray on DNA and subsequent repair by C3H10T1/2 cells (mouse embryo fibroblasts) were investigated. Two versions of the comet assay, a sensitive method for evaluating DNA damage, were implemented: the alkaline one to detect single-strand breaks, and the neutral one to identify double-strand breaks. The results show a good linear relation between DNA damage and radiation dose, for both single-strand and double-strand breaks. A statistically significant difference with respect to controls was found at the lowest dose of 1 Gy. Heterogeneity in DNA damage within the cell population was observed as a function of radiation dose. Repair kinetics showed that most of the damage was repaired within 2 h after irradiation, and that the highest rejoining rate occurred with the highest dose (10 Gy). Single-strand breaks were completely repaired 24 h after irradiation, whereas residual double-strand breaks were still present. This finding needs further investigation.
电离辐射是一种强大的DNA损伤诱导剂，因为它会导致单链和双链断裂、碱不稳定位点、碱基损伤和交联。对电离辐射的关注源于其环境和临床意义。单链断裂是遗传毒性剂诱导的初始损伤，可作为暴露的生物标志物，而更具生物学相关性的双链断裂可用于分析以量化损伤程度。在本研究中，研究了137CSγ辐射剂量为1、5和10格雷对C3H10T1/2细胞（小鼠胚胎成纤维细胞）DNA的影响以及随后的修复情况。实施了两种版本的彗星试验，这是一种评估DNA损伤的灵敏方法：碱性试验用于检测单链断裂，中性试验用于识别双链断裂。结果表明，单链和双链断裂的DNA损伤与辐射剂量之间均呈现良好的线性关系。在最低剂量1格雷时，与对照组相比发现有统计学显著差异。观察到细胞群体内DNA损伤的异质性是辐射剂量的函数。修复动力学表明，大部分损伤在照射后2小时内得到修复，且最高剂量（10格雷）时的重新连接率最高。单链断裂在照射后24小时完全修复，而双链断裂仍有残留。这一发现需要进一步研究。
