4,6-Diamino-5-formamidopyrimidine, 8-hydroxyguanine and 8-hydroxyadenine in DNA from neoplastic liver of English sole exposed to carcinogens.

Attack of the hydroxyl radical on the 8-carbon of guanine results in the formation of 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua). This modified nucleotide was recently found in neoplastic livers of wild English sole exposed to aromatic hydrocarbons (Malins et al., Carcinogenesis, 11, 1045-1047, 1990). Gas-chromatographic-mass spectrometric evidence reported here indicates that three other modified nucleotides are also present in the neoplastic liver: 4,6-diamino-5-formamidopyrimidine, 8-hydroxyguanine and 8-hydroxyadenine. These findings support the hypothesis that the purine nucleotides were modified by the hydroxyl radical and that these changes play a crucial role in tumor formation.