Dietary modifications affecting the mutagenicity of N-nitroso compounds in the host-mediated assay

The effects of various dietary modifications on the mutagenicity of dimethylnitrosamine (DMNA), N-nitrosomorpholine, and N-methyl-N-nitrosourea for Salmonella typhimurium his G-46 in the host-mediated assay were studied. The diets used were:chow, complete semisynthetic, protein-free, and all-casein, in addition to a 24-hr starvation regimen. The mutagenicity of DMNA and N-nitrosomorpholine, which require metabolic activation for their biological activity, was depressed by the complete semisynthetic diet, as compared to the mutagenicity in mice fed the chow diet. DMNA mutagenicity was depressed by the protein-free diet and enhanced by pure casein as compared with the complete semisynthetic diet. N-Nitrosomorpholine mutagenicity was enhanced by starvation, but results with mice fed the protein-free and all-casein diets were ambiguous. N-Methyl-N-nitrosourea, which does not require metabolic activation for its biological activities, responded in an opposite manner to that of DMNA; its mutagenicity was enhanced by the complete semisynthetic and protein-free diets, but was depressed by the all-casein diet.