Heilmann J, Rink H, Taucher-Scholz G, Kraft G
Biophysik, GSI Darmstadt, Germany.
Radiat Res. 1993 Jul;135(1):46-55.
The induction of intracellular DNA strand breaks by X rays and various heavy charged particles was measured by the alkaline unwinding and alkaline and neutral filter elution techniques. No variations in strand break induction were found between the different cell lines under investigation. For a given particle, both the LET and the particle energy determined the efficiency to induce DNA lesions. RBE values for the total amount of induced strand breaks were always less than 1. For DNA double-strand breaks (DSBs), RBE values only slightly greater than 1 were determined for particle radiation with an LET around 300 keV/microns. Intracellular DSB/SSB ratios were found to be equivalent to data reported for in vitro systems using radioprotective conditions [Christensen et al., Int. J. Radiat. Biol. 22, 457-477, 1972; Taucher-Scholz et al., Adv. Space Res. 12(2-3), (2)73-(2)80, 1992]. Strand break rejoining as an indicator of cellular repair processes was detected even after high-LET irradiation (LET < or = 10,000 keV/microns). However, both the half-times of rejoining and the fraction of residual DNA breaks increased with the atomic number of the particle. After particle irradiation with LET values beyond 10,000 keV/microns, no rejoining of DNA strand breaks was found.
采用碱性解旋及碱性和中性滤膜洗脱技术，测定了X射线及各种重带电粒子诱导的细胞内DNA链断裂情况。在所研究的不同细胞系之间，未发现链断裂诱导存在差异。对于给定的粒子，传能线密度（LET）和粒子能量均决定了诱导DNA损伤的效率。诱导的链断裂总量的相对生物效应（RBE）值始终小于1。对于DNA双链断裂（DSB），对于LET约为300 keV/μm的粒子辐射，测定的RBE值仅略大于1。发现细胞内DSB/SSB比值与使用辐射防护条件的体外系统所报告的数据相当[克里斯蒂安森等人，《国际辐射生物学杂志》22，457 - 477，1972；陶彻 - 朔尔茨等人，《空间研究进展》12(2 - 3)，(2)73 - (2)80，1992]。即使在高LET辐射（LET≤10,000 keV/μm）后，也检测到了作为细胞修复过程指标的链断裂重接。然而，重接的半衰期和残留DNA断裂的比例均随粒子的原子序数增加而增加。在用LET值超过10,000 keV/μm的粒子辐照后，未发现DNA链断裂的重接。
