Liu Zhengfeng, Mothersill Carmel E, McNeill Fiona E, Lyng Fiona M, Byun Soo Hyun, Seymour Colin B, Prestwich William V
Medical Physics and Applied Radiation Sciences Department, McMaster University, Hamilton, Ontario, Canada L8S 4K1.
Radiat Res. 2006 Jul;166(1 Pt 1):19-23. doi: 10.1667/RR3580.1.
The existence of radiation-induced bystander effects mediated by diffusible factors is now accepted, but the mechanisms and precise behavior at low doses remain unclear. We exposed cells to gamma-ray doses in the range 0.04 mGy-5 Gy, harvested the culture medium, and transferred it to unirradiated reporter cells. Calcium fluxes and clonogenic survival were measured in the recipients. We show evidence for a dose threshold around 2 mGy for the human skin cell line used with a suggestion of increased survival below that dose. Similar experiments using direct gamma irradiation showed no reduction in survival until the dose exceeded 7 mGy. Preliminary data for neutrons where the gamma-ray dose was kept below the bystander threshold do not show a significant bystander effect in the dose range 1-33 mGy. A lack of a bystander response with neutrons occurred at around 1 Gy, where significant cell killing from direct irradiation was observed. The result may have implications for understanding the role of bystander effects at low doses.
由可扩散因子介导的辐射旁效应的存在现已得到认可，但低剂量时的机制和精确行为仍不清楚。我们将细胞暴露于0.04毫戈瑞至5戈瑞范围内的伽马射线剂量下，收集培养基，并将其转移至未受辐照的报告细胞中。在受体细胞中测量钙通量和克隆形成存活率。我们发现，对于所使用的人类皮肤细胞系，存在一个约2毫戈瑞的剂量阈值，低于该剂量时存活率有增加的迹象。使用直接伽马辐照的类似实验表明，直到剂量超过7毫戈瑞，存活率才会降低。在伽马射线剂量保持在旁效应阈值以下时，对中子的初步数据显示，在1至33毫戈瑞剂量范围内没有明显的旁效应。在约1戈瑞时未出现中子的旁效应反应，此时观察到直接辐照导致了显著的细胞杀伤。该结果可能对理解低剂量时旁效应的作用有影响。
