THE IRRADIATION OF V79 MAMMALIAN-CELLS BY PROTONS WITH ENERGIES BELOW 2-MEV .2. MEASUREMENT OF OXYGEN ENHANCEMENT RATIOS AND DNA DAMAGE

The effectiveness of low-energy (below 2 MeV) protons at inducing DNA damage in the form of single- and double-strand breaks has been determined. Protons with mean energies of 1.90 MeV, 1.15 MeV and 0.76 MeV corresponding to track average LETs of 17 keV/μm, 24 keV/μm and 32 keV/μm, respectively, have been used and compared with 250 kVp X-rays and 3.8 MeV 238Pu αparticles. Although there was variation in the RBE for DNA ssb induction with LET, the RBEs for dsb induction at all three proton energies and for 3.8 MeV αparticles were all around 1.0. This suggests that, if DNA dsb are important in radiation-induced cell lethality, the probability of an induced dsb leading to a lethal event increases with increasing LET of radiation. Oxygen enhancement ratios were measured for both cell survival and DNA dsb induction, and in both cases a decrease in OER with increasing LET was observed. © 1990 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.