Collect. Czech. Chem. Commun. 1995, 60, 2189-2199

Cytochrome P-450 and Peroxidase Oxidize Detoxication Products of Carcinogenic Aristolochic Acids (Aristolactams) to Reactive Metabolites Binding to DNA in vitro

Marie Stiborov√°a, Eva Freib, Heinz H. Schmeiserb and Manfred Wiesslerb

a Department of Biochemistry, Charles University, 128 40 Prague 2, Czech Republic
b Department of Molecular Toxicology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany


We report the analysis of DNA adducts formed from aristolactams I and II, which are the final metabolites derived from carcinogenic aristolochic acids in vivo, after their oxidation by microsomal cytochrome P-450 and horseradish peroxidase in vitro. DNA adducts were detected and quantified using the nuclease P1-enhanced variation of the 32P-postlabeling assay. Quantitative analysis revelead that the extent of modification of DNA by aristolactams activated by peroxidase was more than one order of magnitude higher than for activation by microsomal cytochrome P-450. Peroxidase catalyzes the formation of active oxygen in the presence of NADH, H2O2 and aristolactams. Aristolactams are also oxidized by mammalian peroxidase prostaglandin H synthase. The possible role of aristolactams in carcinogenesis induced by aristolochic acid is discussed.