The irradiation of V79 mammalian cells by protons with energies below 2 MeV. Part II. 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/microns, 24 keV/microns and 32 keV/microns, respectively, have been used and compared with 250 kVp X-rays and 3.8 MeV 238Pu alpha-particles. 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 alpha-particles 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.
Prise
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KM
Grey Laboratory, Mount Vernon Hospital, Northwood, Middlesex, UK.
Folkard
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M
Davies
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S
Michael
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BD
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D006224:Cricetinae; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004277:DNA, Single-Stranded / Q000528:radiation effects; D004735:Energy Transfer; D010100:Oxygen / Q000494:pharmacology*; D011522:Protons; D012062:Relative Biological Effectiveness
D004277:DNA, Single-Stranded; D011522:Protons; D004247:DNA; D010100:Oxygen