Synergistic effect of diethylstilbestrol on the mutagenicity of 2-acetylaminofluorene and N-hydroxy-acetylaminofluorene in the Salmonella assay system.

Salmonella typhimurium, TA-1538, was used to investigate the mutagenic potential of N-2-acetylaminofluorene (2-AAF), N-hydroxy-N-2-acetylaminofluorene (N-OH-2-AAF) and diethylstilbestrol (DES) individual and in combination. In the presence of an induced or uninduced rat liver metabolizing system (S-9), the histidine requiring strain of bacteria was reverted to prototrophy by the aromatic amines but not by the synthetic estrogen. However, when DES was combined with 2-AAF or N-OH-I-AAF in the presence of the induced S-9 fraction, the number of revertant colonies was increased 2- to 4-fold above the levels obtained with the aromatic amines alone. The synergistic effect of DES, a non-mutagen, on the mutagenicity of these aromatic amines was observed only when a 3-methylcholanthrene induced rat liver S-9 fraction was used as the source of mammalian enzymes. When uninduced mouse or rat liver S-9 fractions were used in this test system, an inhibitory effect rather than an enhancing effect was observed.