A new assay for the microsomal metabolism of nitrosamines

This report describes a new general assay for the microsomal oxidative dealkylation of nitrosamines. After precipitation of the microsomal proteins, aldehydes formed from nitrosamines are quantitated by high-pressure liquid chromatography as their 2,4-dinitrophenylhydrazones. This novel assay method offers some distinct advantages over the commonly used Nash reagent assay. Dimethylnitrosamine, diethylnitrosamine, and methylethylnitrosamine were metabolized by microsomes from noninduced male Fischer rat liver, and the aldehydes produced by these reactions were examined. Two distinct kinetic lines were observed for reactions containing dimethylnitrosamine or diethylnitrosamine. Similarly, two Km's were observed for the production of both formaldehyde and acetaldehyde produced by the metabolism of methylethylnitrosamine.