Vitamin C, Added after Irradiation, Reduces the Mutant Yield and Alters the Spectrum of CD59~- Mutations in A_L Cells Irradiated with High LET Carbon Ions

摘要

Miazaki, Watanabe, Kumagai and their colleagues reported that induction of HPRT" mutants by X-rays in cultured human cells was prevented by vitamin C (ascorbate) added 30 minutes after irradiation. They provided data that that mutation extinction was due to neutralization by vitamin C of radiation-induced long-lived mutagenic radicals (LLR) with half-lives of several hours. We find that post-irradiation treatment with vitamin C reduces, but does not eliminate, the induction of CD59" mutants in human-hamster hybrid A_L cells exposed to high-LET carbon ions (LET of 100 KeV/μm) . The lethality of the carbon ions was not altered by vitamin C. Preliminary experiments indicate that post-radiation addition of vitamin C also changes the quality of CD59" mutations induced by the carbon beam . The change in spectrum is seen as a reduction in prevalence of small mutations (not detectable by PCR) and of mutants displaying transmissible genomic instability (TGI) measured by chromosome translocation frequencies. Our results confirm the essential .effect of vitamin C on X-ray induced mutation and suggest a role for LLR in genomic instability.