Comparisons of mutation frequencies and cytotoxic responses of V79 and G12 cells exposed to x rays and alpha particles

Chinese hamster V79 cells and a pSW2gpt transformed UV-induced HPRT-deficient V79 cell line (G12) were exposed to alpha-particles or X rays to analyze sensitivity to the induction of mutations at the HPRT and gpt loci. Alpha-particles are a type of densely ionizing radiation that mainly Interact directly with DNA, while X rays are typical of sparsely ionizing radiation and mainly interact indirectly with DNA through the formation of free radicals. Suspended and attached cells were exposed to alpha-particles in order to study the effects of nuclear shape on the induction of mutations. In addition to analyzing the induction of 6-thioguanine resistant V79 and G12 cells, the cytotoxicity to V79 and G12 cells was also analyzed immediately, 3, and 6 days after exposure to X rays or alpha-particles. There were no significant differences in the mutation frequency in V79 cells induced by exposure to either X rays or alpha-particles at equitoxic doses. In contrast, the mutation frequency of G12 cells exposed to X rays was significantly greater than the mutation frequency of G12 cells exposed to alpha-particles at equitoxic doses. Mutation frequencies of V79 and G12 cells exposed to alpha-particles were similar. The mutation frequency of G12 cells was significantly higher than that of V79 cells when exposed to X rays. These preliminary results suggest possible differences in the sensitivity to the induction of gpt mutations in G12 cells when exposed to X rays compared to alpha-particles.