High Energy Proton Induced Mutations in Cultured Chinese Hamster Cells

Summary

Chinese Hamster (V79) cells were assayed for cell survival as measured by colony forming ability and for mutation at the hypoxanthine guanine phosphoribosyl transferase (HGPRT) locus as measured by resistance to 6-thioguanine (6-TG) after exposure to 160 MeV protons delivered at low dose rates at the Harvard University Cyclotron. Proton irradiations were carried out at three dose rates; 20, 0.5 and 0.1 rad/min. Preliminary results indicate that no difference exists between these radiations when cell survival was examined, but that low doses of protons delivered at low dose rates were more effective than higher doses in inducing mutations at the HGPRT locus. Indeed our initial results showed a peak in induced mutations at a dose of 5 rad delivered at a dose rate of 0.1 rad/min. When the proton dose was delivered at a dose rate of 20 rad/min. a dose of 40 rad was required to equal the mutation frequency observed for 5 rad delivered at 0.1 rad/min. This enhanced effect for low doses delivered at a low dose rate is similar to that reported by Hill et al. (1982) for transformation of 10T 1/2 cells by low doses of neutrons delivered at low dose rates.