On the metabolic activation of the carcinogen N-hydroxy-N-2-acetylaminofluorene : III. Oxidation with horseradish peroxidase to yield 2-nitrosofluorene and N-acetoxy-N-2-acetylaminofluorene

Previous studies have shown that the carcinogen N-hydroxy-2-acetylaminofluorene is converted by one-electron oxidants to a free nitroxide radical which dismutates to N-acetoxy-2-acetylaminofluorene and 2-nitrosofluorene. The present study shows that the same oxidation can be achieved with horseradish peroxidase and H₂O₂. The free radical intermediate was detected by its ESR signal, and the yields of N-acetoxy-2-acetylaminofluorene and of 2-nitrosofluorene were determined under a number of conditions. Addition of tRNA to the reaction mixture containing N-acetoxy-N-2-acetyl[2′-³H]aminofluorene yielded tRNA-bound radioactivity; addition of guanosine yielded a reaction product which appears to be N-guanosin-8-yl)-2-acetylaminofluorene. The latter compound has previously been identified as a reaction product of N-acetoxy-2-acetylaminofluorene and guanosine. Preliminary attempts to demonstrate the formation of a nitroxide free radical or its dismutation products with rat liver mixed function oxidase systems were not successful.