Aoki M, Furusawa Y, Yamada T
Space and Particle Radiation Science Research Group, National Institute of Radiological Sciences, Chiba, Japan.
J Radiat Res. 2000 Jun;41(2):163-75. doi: 10.1269/jrr.41.163.
We investigated the relationship between the LET values and cell death, defined as either apoptosis or loss of reproductive integrity (reproductive death), using Chinese hamster V79 cells. The cells were irradiated with X-rays or carbon-ion beams from the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). Apoptosis was defined based on the morphological change upon treating of cells with caffeine. The apoptotic index, the ratio of apoptotic cells to the total, after exposure to 2 Gy of X-rays was 0.043. Upon irradiation with carbon-ion beams, the index was gradually increased with increasing LET values, reaching a maximum of 0.076 at 110 keV/micron, and then decreased to 0.054 at 237 keV/micron. An analogous pattern of the LET dependence was observed between reproductive death and apoptotic death. The cell-survival values obtained after 2 Gy exposure (SF2) were 0.64, 0.13, and 0.24, respectively. A similar trend was found for the RBE values calculated from the initial slope for both apoptosis and reproductive death. These results strongly suggest that the target for both types of cell death is the same.
我们使用中国仓鼠V79细胞研究了传能线密度（LET）值与细胞死亡之间的关系，细胞死亡定义为凋亡或生殖完整性丧失（生殖死亡）。细胞用来自日本国立放射科学研究所（NIRS）千叶重离子医学加速器（HIMAC）的X射线或碳离子束进行照射。凋亡是根据用咖啡因处理细胞后的形态变化来定义的。在接受2 Gy X射线照射后，凋亡指数（凋亡细胞与总细胞的比率）为0.043。在用碳离子束照射时，该指数随着LET值的增加而逐渐升高，在110 keV/微米时达到最大值0.076，然后在237 keV/微米时降至0.054。在生殖死亡和凋亡死亡之间观察到类似的LET依赖性模式。在2 Gy照射后获得的细胞存活值（SF2）分别为0.64、0.13和0.24。从凋亡和生殖死亡的初始斜率计算出的相对生物效应（RBE）值也发现了类似趋势。这些结果有力地表明，这两种类型的细胞死亡靶点是相同的。
