Ikebuchi M, Kimura H, Hill C K, Aoyama T
Department of Experimental Radiology, Shiga University of Medical Science, Otsu, Japan.
Radiat Res. 1995 Jan;141(1):19-27.
X rays have been shown to induce two forms of potentially lethal damage (PLD), "fast-repairing" PLD and "slowly repairing" PLD, whose repair is completed in 1 h and 4-6 h, respectively. In this study three modes of treatment with hypertonic solutions containing different NaCl concentrations for different durations (0.5 M for 30 min, 0.225 M for 4 h, 0.16 M for 16 h) were examined to determine which form of PLD is expressed under each condition. These three modes of treatment enhanced the cell-killing action of X rays on actively growing V79 cells due to fixation of PLD. The kinetics of recovery from PLD was assessed by delayed treatments with hypertonic solutions. Cells exposed to one of the three treatments (see above) had completed recovery times of 1, 4 and 8 h, respectively, suggesting the possibility that these three modes of treatment cause the expression of different forms of PLD. As has been reported, treatment with 0.5 M NaCl for 30 min expressed fast-repairing PLD. The independence of the PLD expressed by 0.225 M NaCl for 4 h from fast-repairing PLD expressed after 0.5 M NaCl for 30 min was shown by combined treatment with the two modes, which reduced survival to the level that would be reached if the two modes acted independently. The data on the recovery time and on the inhibition by 0.225 M NaCl of recovery from slowly repairing PLD in plateau-phase cells indicated that the PLD expressed after 0.225 M NaCl for 4 h may be related to slowly repairing PLD. The combined treatment of 0.16 M NaCl for 16 h with 0.225 M NaCl for 4 h indicated independent action, albeit incomplete, of the PLD expressed after 0.16 M NaCl for 16 h from slowly repairing PLD. We propose for the first time that "very slowly repairing" PLD is expressed after 0.16 M NaCl for 16 h in exponentially growing cells and that therefore three forms of PLD are expressed by hypertonic treatments after X irradiation.
X射线已被证明可诱导两种潜在致死性损伤（PLD），即“快速修复”PLD和“缓慢修复”PLD，其修复分别在1小时和4 - 6小时内完成。在本研究中，研究了三种用含有不同NaCl浓度的高渗溶液进行不同持续时间（0.5M，30分钟；0.225M，4小时；0.16M，16小时）的处理方式，以确定在每种条件下表达的是哪种形式的PLD。由于PLD的固定，这三种处理方式增强了X射线对活跃生长的V79细胞的杀伤作用。通过用高渗溶液进行延迟处理来评估从PLD恢复的动力学。接受三种处理之一（见上文）的细胞分别具有1小时、4小时和8小时的完全恢复时间，这表明这三种处理方式可能导致不同形式PLD的表达。正如所报道的，用0.5M NaCl处理30分钟表达快速修复的PLD。通过两种方式的联合处理表明，0.225M NaCl处理4小时所表达的PLD与0.5M NaCl处理30分钟后所表达的快速修复PLD无关，联合处理使存活率降低到两种方式独立作用时所达到的水平。关于恢复时间以及0.225M NaCl对处于平台期细胞中缓慢修复PLD恢复的抑制的数据表明，0.225M NaCl处理4小时后所表达的PLD可能与缓慢修复的PLD有关。0.16M NaCl处理16小时与0.225M NaCl处理4小时的联合处理表明，0.16M NaCl处理16小时后所表达的PLD与缓慢修复的PLD虽不完全独立但有独立作用。我们首次提出，在指数生长的细胞中，0.16M NaCl处理16小时后表达“非常缓慢修复”的PLD，因此X射线照射后高渗处理可表达三种形式的PLD。
