The Effect of Dietary Protein Deficiency on the Ability of Isolated Hepatic Microsomes to Alter the Mutagenicity of a Primary and a Secondary Carcinogen¹

The capacity of isolated microsomes to alter mutagenicity for bacteria of the primary carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine, and the secondary one, dimethylnitrosamine, was studied. Microsomal inactivation of N-methyl-N'-nitro-N-nitrosoguanidine and activation of dimethylnitrosamine were decreased by protein-and protein-choline-deficient diets, and this decrease paralleled the reduction in microsomal cytochrome P-450 content produced by these diets. The results obtained with this in vitro assay indicate that the status of the microsomal biotransformation system that can be influenced by nutritional factors determines the mutagenicity of the primary and secondary carcinogens tested.