摘要：The relationship between the inhibitory effects of water soluble vitamins and SH compounds on the formation of O6-methyldeoxyguanosine (MedGuo) and on the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated. Thiamine (B1), riboflavin (B2), pyridoxine (B6), nicotinamide, ascorbic acid (AsA) and dehydroascorbic acid (DHA) were selected as water soluble vitamins, and cysteine (Cys) and glutathione (GSH) were also selected as SH compounds. In the experiments of the inhibitory effects of the compounds on the formation of O6-MedGuo, MNNG, 2'-deoxyguanosine and each of the above compounds were incubated at 37°C for 6 h, and the resulting O6-MedGuo was derivatized to the fluorescent compound. Then, the fluorophore was determined by HPLC, and the formation ratio (%) of O6-MedGuo was calculated and compared to that in the reaction without vitamin or SH compound. By the addition of SH compounds (100-folds molar of MNNG), the amounts of the formed O6-MedGuo was depressed to less than 10%. The inhibitory effects of AsA and DHA on the formation of O6-MedGuo were greater than those of other vitamins. The desmutagenic effects of AsA and Cys on the mutagenicity of MNNG in Salmonella typhimurium TA 100 were observed, and the mutagenicity was reduced to 10% or less by the addition of equimolar AsA and Cys to MNNG. The desmutagenic effects of B1, B2 and B6 on MNNG were not observed.
