Induction of point mutations by different chemical mechanisms in the liver microsomal assay

A selection of chemical agents with different mechanisms of chemical mutability was tested with the liver microsomal assay by using different bacterial tester strains, namely: Salmonella typhimurium TA 1535, TA 1536, TA 1537, TA 1538 and G46. The tested agents had been selected according to the following criteria. They are all well-known mutagens and can be divided into alkylating agents, anti-metabolites, acridines and those that form radicals in the cell. The mutagens were: dimethylnitrosamine (DMN), diethylnitrosamine (DEN), methyl-nitro-nitrosoguanidine (MNNG), cyclophosphamide, Captan, amethopterine, azathioprine, 6-mecaptopurine, trypaflavine, isoniazide and hydrazine. All except amethopterine gave positive results, showing that this system is very sensitive. In a comparison of the different strains and mutagens we found a correlation between the diameter of the molecule and the permeability of the bacterial cell membrane.