低剂量辐射诱导小鼠胸腺细胞DNA裂解适应性反应的剂量率效应

目的：观察低剂量辐射诱导胸腺细胞DNA裂解适应性反应的剂量率效应。方法：用X射线照射Kunming雄性小鼠，其诱导剂量（D1）及其后攻击剂量（D2）分别是75 mGy和1.5 Gy，D1剂量率为6.25、12.5、25、50、100和200 mGy•min^-1，D2剂量率为287 mGy•min^-1，D1 和D2间隔6 h。通过荧光分光光度计检测DNA裂解断片的变化。结果：D2组胸腺细胞DNA裂解率明显高于假照组（P<0.001）；当D1剂量率为6.25、12.5和25 mGy•min^-1，D1＋D2组DNA裂解率明显低于D2组（P<0.05或P<0.01）。结论：当D1在75 mGy，剂量率为6.25～25 mGy•min^-1；D2为1.5 Gy，剂量率为287 mGy•min^-1；D1和D2间隔6 h，可在全身照射条件下诱导小鼠胸腺细胞DNA裂解的适应性反应。

Dose-rate effects of adaptive response of thymocyte DNA lysis induced by low dose ionizing radiation in mice

Objective To observe the dose-rate effects of adaptive response of thymocyte DNA lysis induced by low dose radiation. Methods Kunming male mice were irradiated with the inductive dose (D1: 75 mGy; dose rate: 6.25, 12.5, 25, 50, 100, and 200 mGy·min -1 ) and the challenging dose (D2: 1.5 Gy; dose rate: 287 mGy·min -1 ) , the interval between D1 and D2 was 6 hours. The DNA lytic fragmentation was measured with fluorospectrophotometry. Results The DNA lytic rate in the D2 group was significantly higher than that in sham-irradiation group; when the dose rates were 6.25, 12.5 and 25 mGy·min -1 ,the DNA lytic rates in D1+D2 groups were significantly lower than those in the D2 group (P<0.05 or P<0.01). Conclusion When the mice are irradiated with 75 mGy (D1: 6.25~25 mGy·min -1 ) 6 hours before 1.5 Gy (D2: 287 mGy·min -1 ) exposure, the adaptive response of thymocyte apoptosis can be induced under the condition of whole-body irradiation.