Dini Valentina, Antonelli Francesca, Belli Mauro, Campa Alessandro, Esposito Giuseppe, Simone Giustina, Sorrentino Eugenio, Tabocchini Maria Antonella
Istituto Superiore di Sanità, 00161 Roma, Italy.
Radiat Res. 2005 Oct;164(4 Pt 2):577-81. doi: 10.1667/rr3348.1.
In the framework of a collaborative project on the influence of the shielding on the biological effectiveness of space radiation, we studied DNA fragmentation induced by 1 GeV/nucleon iron ions and titanium ions with and without a 197-mm-thick polymethylmethacrylate (PMMA) shield in AG1522 human fibroblasts. Pulsed- and constant-field gel electrophoresis were used to analyze DNA fragmentation in the size range 1-5700 kbp. The results show that, mainly owing to a higher production of small fragments (1-23 kbp), titanium ions are more effective than iron ions at inducing DNA double-strand breaks (DSBs), their RBE being 2.4 and 1.5, respectively. The insertion of a PMMA shield decreases DNA breakage, with shielding protection factors (ratio of the unshielded/shielded cross sections for DSB production) of about 1.6 for iron ions and 2.1 for titanium ions. However, the DSB yield (no. of DSBs per unit mass per unit dose) is almost unaffected by the presence of the shield, and the relative contributions of the fragments in the different size ranges are almost the same with or without shielding. This indicates that, under our conditions, the effect of shielding is mainly to reduce the dose per unit incident fluence, leaving radiation quality practically unaffected.
在一个关于屏蔽对空间辐射生物有效性影响的合作项目框架内，我们研究了在AG1522人成纤维细胞中，有无197毫米厚的聚甲基丙烯酸甲酯（PMMA）屏蔽时，1 GeV/核子的铁离子和钛离子诱导的DNA片段化情况。采用脉冲场凝胶电泳和恒场凝胶电泳分析了大小在1 - 5700 kbp范围内的DNA片段化。结果表明，主要由于较小片段（1 - 23 kbp）产量较高，钛离子在诱导DNA双链断裂（DSB）方面比铁离子更有效，它们的相对生物效能（RBE）分别为2.4和1.5。插入PMMA屏蔽可减少DNA断裂，铁离子的屏蔽保护因子（DSB产生的无屏蔽/有屏蔽截面之比）约为1.6，钛离子约为2.1。然而，DSB产额（每单位质量每单位剂量的DSB数量）几乎不受屏蔽存在的影响，并且有无屏蔽时不同大小范围内片段的相对贡献几乎相同。这表明，在我们的条件下，屏蔽的作用主要是降低每单位入射注量的剂量，而辐射品质实际上未受影响。
