Induction of DNA-protein crosslinks in Chinese hamster V79-4 cells exposedto high- and low-linear energy transfer radiation

The induction of DNA-protein crosslinks (DPCs) in Chinese hamster V79-4 cel ls after irradiation under hypoxic and aerobic conditions at 277 K with Co- 60 gamma rays, Pu-238 alpha particles and aluminum K (Al-K) ultrasoft X ray s has been determined using a nitrocellulose filter binding assay. The dose dependences for the induction of DPCs, which involves covalent linkage, ar e linear over the absorbed dose range used (0-400 Gy with alpha-particle an d gamma radiation, 0-600 Gy with Al-K X rays). The yield of DPCs induced un der hypoxic conditions is 55, 51 and 25 DPCs per gray per cell for Co-60 ga mma rays, alpha particles and Al-K X rays, respectively. The yield of DPCs is significantly reduced in the presence of oxygen by 20, 50 and 79% for Co -60 gamma rays, alpha particles and Al-K X rays, respectively. Since the me an size of the DNA attached to the protein is uniform for Co-60 gamma rays and alpha particles, variations in the DNA size do not influence the yields of DPCs. Although a DPC may be considered as a complex lesion combining tw o macromolecules, the dependence of the yield of DPCs on LET does not refle ct the ionizing density of the radiations used. Further, this dependence on LET and the effect of oxygen do not reflect the corresponding dependences determined for a variety of biological responses. From these findings and k nowledge of the radiation tracks, it is proposed that DPCs induced particul arly under aerobic conditions with Co-60 gamma rays are formed mainly in th e sparsely ionizing segments of the radiation track. (C) 1998 by Radiation Research Society.