Effects of bile acids on the mutagenicity and recombinogenicity of triethylene melamine in yeast strains MP1 and D61.M.

When Saccharomyces cerevisia MP1 was treated with bile acids alone or in combination with triethylene melamine (TEM), cholic acid was found to be comutagenic and antirecombinogenic while lithocholic acid had the opposite effect. Other bile acids enhanced the mutagenic and recombinogenic effects of TEM. Chenodeoxycholic acid, deoxycholic acid and ursodeoxycholic acid had stronger comutagenic than corecombinogenic effects; hyodeoxycholic acid did not show this difference. Ox gall and a mixture of bile acids antagonized the genotoxic effect of TEM, and it therefore seems plausible that in normal composition bile acids neutralize each other, i.e., the comutagenic (corecombinogenic) effect of one substance is antagonized by the antimutagenic (antirecombinogenic) effect of another one. However, when the composition is altered, bile acids may become harmful. Experiments with yeast strain D61.M were performed in order to test for aneuploidy caused by bile acids; no effects were observed.