Anti-mutagenic agents are also co-recombinogenic and can be converted into co-mutagens

In experiments using yeast without an external metabolic activation system, the hormones testosterone, beta-estradiol and diethylstilbistrol were anti-mutagenic and co-recombinogenic. In the presence of Aroclor-induced rat liver S-9 plus cofactors (S9-mix) the same substances acted as co-mutagens and anti-recombinogens. Since an external metabolic activation system was able to convert anti-mutagens into co-mutagens, we studied whether the different metabolism of yeast and mice would lead to different effects. In whole-animal experiments using the mouse spot test, anti-mutagenic effects of vanillin (...), phenobarbital (...), and tannic acid (...) have been observed. In our present experiments with yeast, tannic acid and phenobarbital showed anti-mutagenic effects also, whereas vanillin acted as a co-mutagen. Thus, as in the case of the hormones, tannic acid and phenobarbital were anti-mutagenic and co-recombinogenic whereas vanillin was co-mutagenic as well as co-recombinogenic.