Mechanism of Aralkyl-DNA Adduct Formation from Benzo[a]pyrene in vivo

• Published in: Chemical research in toxicology 1994-03, Vol.7 (2), p.254-259
• Main Authors: Stansbury, Kevin H, Flesher, James W, Gupta, Ramesh C
• Format: Article
• Language: English
• Subjects: 550200 - Biochemistry; 560300 - Chemicals Metabolism & Toxicology; ADDUCTS; AMINES; ANIMALS; AROMATICS; AZAARENES; BASIC BIOLOGICAL SCIENCES; Benzo(a)pyrene - administration & dosage; Benzo(a)pyrene - metabolism; BENZOPYRENE; BIOCHEMICAL REACTION KINETICS; Biological and medical sciences; BIOLOGICAL PATHWAYS; CARCINOGENESIS; Carcinogenesis, carcinogens and anticarcinogens; Chemical agents; Chromatography, Thin Layer; CONDENSED AROMATICS; DNA - metabolism; DNA ADDUCTS; Female; GUANINE; HETEROCYCLIC COMPOUNDS; HYDROCARBONS; HYDROXY COMPOUNDS; Injections, Subcutaneous; KINETICS; MAMMALS; Medical sciences; METABOLIC ACTIVATION; NUCLEOTIDES; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; PATHOGENESIS; POLYCYCLIC AROMATIC HYDROCARBONS; PURINES; RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT; RATS; Rats, Sprague-Dawley; REACTION KINETICS; RODENTS; Tumors; VERTEBRATES
• ISSN: 0893-228X; 1520-5010
• DOI: 10.1021/tx00038a019

Three different pathways have been proposed for the metabolic activation of the ubiquitous polycyclic aromatic hydrocarbon, benzo[a]pyrene (BP). The most widely accepted activation mechanism is based on ring oxidation to diol epoxides; the other two relatively less studied pathways involve radical cation formation and benzylic electrophilic ester formation arising from a chain of substitution reactions. The present study was undertaken to test for the existence of the latter mechanism in vivo. Female Sprague-Dawley weanling rats were injected subcutaneously with 320 mumol of BP/kg body weight, and the formation of DNA adducts was examined. 32P-Postlabeling analysis of the subcutaneous tissue DNA under newly developed chromatography conditions exhibited two sets of adduct profiles: one resulting from alkyl substitution and the other from ring oxidation. One major and two minor aralkyl-DNA adducts were detected. The relative adduct labeling (adducts/10(10) nucleotides) remained constant at around 2 during the first 5 days of treatment and then increased to 6.4 +/- 2.6 at day 7. The corresponding total values of the known ring oxidation (e.g., diol epoxide) adducts were 15-50 times higher. When animals were injected with 6-methyl-BP, 6-(hydroxymethyl)-BP, and 6-(acetoxymethyl)-BP, the known or proposed intermediates in the benzylic ester pathway, each of these and the parent compound showed chromatographically identical profiles of aralkyl-DNA adducts. Cochromatography in multiple solvents of these in vivo adducts with standards prepared by reaction of 6-(bromomethyl)-BP with individual nucleotides showed that the predominant in vivo aralkyl-DNA adduct was derived from guanine while the second major adduct was from adenine.