MEASUREMENTS OF MUTAGENIC AND ANTIMUTAGENIC ACTIVITIES OF BILE-ACIDS BY REC-ASSAY

To study the carcinogenic activity of bile acids, we examined the muta genic activity of bile acids by Rec-assay using B. subtilis H17 and M4 5 strains. Cholic, chenodeoxycholic, lithocholic, and glycolithocholic acids exerted much weaker mutagenicity than mitomicin C (MMC), and de oxycholic and glycodeoxycholic acids showed toxicity toward the bacter ia. Most of the conjugated bile acids (glycocholic, taurocholic, and t aurodexycholic acids) and their amino acid components (glycine and tau rine) were neither toxic nor mutagenic. No bile acids enhanced the mut agenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), but glycine enhanced both toxicity and mutagenicity of MNNG in a dose-dependent ma nner. On the other hand, taurine decreased the mutagenicity of MNNG, a nd most of the bile acids decreased the mutagenicity of MMC. Furthermo re, taurocholic acids decreased toxicity and/or mutagenicity of other bile acids. These results suggested that the mutagenic and comutagenic activities of bile acids can be disregarded, but they are antimutagen ic in some situations.