Influence of oxygen on the induction of DNA strand breaks in mammalian cells by radiations of different LET, and relation to cell killing. 1

The induction of DNA single and double-strand breaks in Chinese hamster cells by radiations of LETs between 1 and 66 keV/μm was investigated under oxic and extremely hypoxic conditions. The results show that at high dose rates a radiation-induced oxygen depletion of the surrounding medium occurs which becomes evident at a γ-dose of about 100 Gy by a break in the dose effect curve. Unlike the survival, the oxygen enhancement ratio for DNA strand breaks does not decrease with increasing LET of the radiation and exhibits a value of about 3 - 4 after all radiations applied. Analogously the release of DNA from the DNA-nuclear membrane complex is clearly dependent on the presence of oxygen during irradiation. (author)