Marchese M J, Hall E J
Am J Clin Oncol. 1984 Dec;7(6):613-6.
Potentially lethal damage repair (PLDR) is considered to be an important mechanism of cellular radioresistance. Studies have suggested that radioresistant human tumor cells may have increased PLDR capability. Studies have also shown that PLDR may be decreased with smaller dose fractions. PLDR occurring with low dose rate continuous irradiation (LDCI) has not been assessed. The C3H/10T1/2 murine cell line in plateau phase (15% cycling fraction) was used to study the effect of dose fraction size and LDCI on PLDR. The cells were found to have substantial PLDR capability. Uncorrected data showed increased PLDR with higher single fractions. However, when the single fraction results are extrapolated to multiple fractions to give equivalent cell survival for the large and small fractions, no difference in PLDR was observed. The data from the LDCI experiments demonstrated some survival enhancement with delayed plating after 5 and 8 hours of irradiation, but not after 16 or more hours. The results indicate that PLDR occurs during the LDCI and that the magnitude of PLDR is similar for LDCI relative to acute irradiation.
潜在致死性损伤修复（PLDR）被认为是细胞抗辐射性的一种重要机制。研究表明，抗辐射的人类肿瘤细胞可能具有增强的PLDR能力。研究还表明，较小的分次剂量可能会降低PLDR。低剂量率连续照射（LDCI）时发生的PLDR尚未得到评估。利用处于平台期（细胞周期比例为15%）的C3H/10T1/2小鼠细胞系来研究分次剂量大小和LDCI对PLDR的影响。发现这些细胞具有显著的PLDR能力。未经校正的数据显示，单次照射剂量越高，PLDR增加。然而，当将单次照射结果外推至多次照射以获得大小分次剂量等效的细胞存活率时，未观察到PLDR有差异。LDCI实验的数据表明，照射5小时和8小时后延迟接种有一定的存活增强，但照射16小时或更长时间后则没有。结果表明，PLDR在LDCI过程中发生，并且相对于急性照射，LDCI的PLDR程度相似。
