Parameters for detection of mutagenesis of 1,2-dimethylhydrazine using an in vitro Bacillus subtilis system

Parameters for detection of mutagenesis of 1,2-dimethylhydrazine (DMH) using a Bacillus subtilis microbial assay are defined. His⁺ and his^*met^* mutations were induced in B. subtilis TKJ6321 in the absence of rat liver S-9 Mix. This B. subtilis mutant showed a greater sensitivity to this chemical than did Salmonella typhimurium TA1535. Protein-binding studies with bovine serum albumin showed the capacity for DMH to bind non-specifically to protein. S-9 Mix from Aroclor^® pretreated animals appeared to decrease the mutagenic response. Kinetics of mutagen stability were also shown, thereby demonstrating the need for more complete investigation of known chemical carcinogens which give negative results in the Ames bioassay alone.