A simple method for assessment of rat cytochrome P-448 isozymes responsible for the mutagenic activation of carcinogenic chemicals.

Cytochrome P-448H/L-enriched and cytochrome P-448L-enriched microsomes were prepared from the livers of Sprague-Dawley rats treated with 3-methylcholanthrene (MC) and with a combination of MC and carbon tetrachloride, respectively, and their activities for mediating mutagenic activation of 9 carcinogenic aromatic amines and benzo[a]pyrene, which are found to be different from cyt. P-450 isozymes as to mutagenic activation, were compared on the basis of microsomal cytochrome P-450 content using Salmonella typhimurium TA98 as a tester bacterium. With regard to the substrate-specificity of cytochrome P-448 isozymes, the present results reflected the reported results with use of a cytochrome P-450-reconstituted system. These findings indicate that the mutation test with cytochrome P-448H/L-enriched and cytochrome P-448L-enriched microsomes could be used as a simple method for the determination of the cytochrome P-448 isozymes responsible for the mutagenic activation of carcinogens and mutagens without the use of a cytochrome P-450-reconstituted system.