Covalent binding of (+) 7S-trans-7,8-dihydrobenzo [a]pyrene-7,8-diol to trout DNA: P-450- and peroxidation-dependent pathways.
Bioactivation in vivo of pure (+) 7S-trans-7,8-dihydrobenzo[a]pyrene- 7,8-diol ((+) BP-7,8-DHD) was investigated in rainbow trout. Embryos, microinjected with 0.01-1.0 microgram of [3H]-(-)-7S-trans-7,8-dihydrobenzo[a]-pyrene-7,8-diol-anti-9,10-epoxide ((-) anti-BPDE), exhibited a dose-dependent increase in DNA adduction. Subsequently, microinjection of trout embryos with [14C] (+) BP-7,8-DHD also demonstrated a dose-dependent increase in DNA adduction. To determine the relative contribution of P-450-dependent versus peroxidation-dependent epoxygenation of (+)-BP-7,8-DHD, trout embryos were co-injected with [14C]-(+)-BP-7,8-DHD and either beta-naphthoflavone (BNF) (CYP1A1 inducer) or carbon tetrachloride (CCl4) (lipid peroxidation enhancer). Co-injection with BNF tended to enhance covalent binding to DNA, which was consistent with rapid induction of CYP1A1. Co-injection with CCl4, significantly increased covalent binding of [14C]-(+)-BP-7,8-DHD to DNA, suggesting a contribution from non-enzymic cooxidation. 32P-Postlabeling analysis of liver DNA adducts following i.p. injections of (+) BP-7,8-DHD did not detect appreciable amounts of (-) anti-BPDE-dG from juvenile trout fed control diets or diets containing hydrogen peroxide or BNF. On the contrary, BNF pre-feeding markedly enhanced the levels of an adduct which co-chromatographed with authentic (+) syn-BPDE-dG. These results confirm that trout are capable of metabolically activating BP-DHD to the ultimate carcinogen BPDE and that BNF stimulates CYP1A1-dependent epoxygenation, but peroxidation-dependent activation may not contribute significantly to the bioactivation of BP-7,8-DHD in vivo.
Kelly
J D
JD
Toxicology Program, Oregon State University, Corvallis 97331-6602.
Dutchuk
M
M
Takahashi
N
N
Reddy
A
A
Hendricks
J D
JD
Williams
D E
DE
D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D001571:Benzoflavones / Q000494:pharmacology; D001665:Binding Sites; D001711:Biotransformation; D002251:Carbon Tetrachloride / Q000494:pharmacology; D019363:Cytochrome P-450 CYP1A1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004247:DNA / Q000187:drug effects / Q000378:metabolism*; D004249:DNA Damage; D004101:Dihydroxydihydrobenzopyrenes / Q000378:metabolism* / Q000633:toxicity; D004625:Embryo, Nonmammalian; D004790:Enzyme Induction / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000378:metabolism; D015227:Lipid Peroxidation; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000096:biosynthesis* / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism; D014337:Trout / Q000378:metabolism*; D019324:beta-Naphthoflavone
D001571:Benzoflavones; D004101:Dihydroxydihydrobenzopyrenes; C017228:benzo(a)pyrene 7,8-dihydrodiol; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D019324:beta-Naphthoflavone; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D006861:Hydrogen Peroxide; D002251:Carbon Tetrachloride; D010088:Oxidoreductases; D010544:Peroxidases; D019363:Cytochrome P-450 CYP1A1