Effects of bile acids on mutation, recombination and induction of chromosome losses in S.cerevisiae

In recent experiments with yeast strain MP1, cocarcinogens were found to be comutagenic and antirecombinogenic and antimutagenic. Substances that were cocarcinogens as well as tumor promoters had an intermediary effect. In course of the present work with S. cerevisiae MP1 using bile acids per se and in combination with triethylene melamine (TEM), of the following substances dose/effect-curves have been established: Deoxycholic acid, chenodeoxycholic acid, ursodeoxycholic acid, cholesterol (control), ox gall, and of mixture of a bile salts. Bile acids showed all three possible ways of action supporting the hypothesis that mutagenesis is the mechanism by which chemicals induce malignancy, and that cocarcinogens modify the process by enhancement of mutagenicity whereas tumor promoters effect carcinogenesis mainly by the increase of the spontaneous frequency of recombination. In addition to this, experiments have been performed with yeast strain D61.M for detection of aneuploidy. In these experiments no effects could be observed. According to the present results it seems furthermore possible that in normal cases bile acids neutralize each other, i.e. the comutagenic (corecombinogenic) effect of one substance is antagonized by the antimutagenic (antirecombinogenic) effect of another one. Only if the balance is lost bile acids may be harmful.