title: Ascorbate enhances u.v.-mutagenesis in E. coli but inhibits it in Chinese hamster cells.
abstract: Ascorbic acid (vitamin C) causes an increase in the mutation frequency of u.v.-irradiated Escherichia coli WP2. The enhancement occurs at all u.v. fluences, and is dependent upon the ascorbate concentration in the medium. A maximum effect (approximately 8- to 13-fold) is seen at 100-150 micrograms/ml, although some enhancement can be seen even at 10 micrograms/ml. The comutagenic effect of ascorbate with u.v. in E. coli is dependent upon peptone, a constituent of nutrient broth. The enhancement of u.v.-mutagenesis by ascorbate is absent in strains WP2s (uvrA) and WP6 (polA), suggesting that ascorbate affects the repair of pyrimidine dimers. The opposite results are observed for u.v.-mutagenesis in Chinese hamster V79 cells. The presence of ascorbate (50 micrograms/ml) during u.v. irradiation does not enhance the u.v. effect, but rather decreases it approximately 30%. These results are discussed with regard to differences in the mechanism of u.v.-mutagenesis and DNA repair in bacterial and mammalian cells.
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000633:toxicity*; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D003470:Culture Media; D004260:DNA Repair / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D009154:Mutation; D014466:Ultraviolet Rays
chemical_list: D003470:Culture Media; D001205:Ascorbic Acid