title: Covalent DNA adducts formed in mouse epidermis by benzo[g]chrysene.
abstract: The metabolic activation in mouse skin of benzo[g]chrysene (B[g]C), a moderately carcinogenic polycyclic aromatic hydrocarbon (PAH) present in coal tar, was investigated. Male Parkes mice were treated topically with 0.5 micromol B[g]C and DNA was isolated from the treated areas of skin at various times after treatment and analysed by 32P-post-labelling. Seven major adduct spots were detected, at a maximum level of 6.55 fmol adducts/microg DNA. Mouse skin treated with the PAH benzo[c]phenanthrene (B[c]Ph) gave a total of 0.24 fmol adducts/microg DNA. B[g]C-DNA adducts persisted in skin for at least 3 weeks. Treatment of mice with 0.5 micromol of the optically pure putative proximate carcinogens, the (+)- and (-)-trans benzo[g]chrysene-11,12-dihydrodiols, led to the formation of adducts which comigrated on TLC and HPLC with those formed in B[g]C-treated mice, which suggested that the detected adducts were formed by the fjord region B[g]C-11,12-dihydrodiol-13,14-epoxides (B[g]CDEs). To test this, the four optically pure synthetic B[g]CDEs were reacted in vitro with DNA and the heteroco-polymers poly(dA x dT) and poly(dG x dC) and these samples 32P-postlabelled. Co-chromatography, on both TLC and HPLC, of in vitro and in vivo adducts indicated that B[g]C is activated in mouse skin through formation of the (-)-anti-(11R,12S,l3S,14R) and (+)-syn-(11S,12R,13S,14R) B[g]CDEs. (-)-anti-B[g]CDE formed five adducts with DNA, two of them with adenine and three with guanine bases. (+)-syn-B[g]CDE formed one adduct with each of these bases in DNA. The adenine adducts accounted for 64% of the total major adducts formed in B[g]C-treated mouse skin. The route of metabolic activation or B[g]C is similar to that reported for B[c]Ph, but the extent of activation to the fjord region diol-epoxides is significantly greater in the case of B[g]C, as demonstrated by the higher levels of adduct formation in vivo.
authors.affiliation: Haddow Laboratories, Institute of Cancer Research, Surrey, UK.
authors.forename: A S
authors.initials: AS
authors.lastname: Giles
authors.forename: A
authors.initials: A
authors.lastname: Seidel
authors.forename: D H
authors.initials: DH
authors.lastname: Phillips
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000378:metabolism* / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D002911:Chrysenes / Q000378:metabolism* / Q000633:toxicity*; D004247:DNA / Q000187:drug effects* / Q000378:metabolism*; D018736:DNA Adducts / Q000096:biosynthesis* / Q000378:metabolism; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009153:Mutagens / Q000378:metabolism* / Q000633:toxicity*; D012867:Skin / Q000187:drug effects* / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D002273:Carcinogens; D002911:Chrysenes; D018736:DNA Adducts; D009153:Mutagens; C089231:benzo(g)chrysene-11,12-dihydrodiol-13,14-epoxide; C100422:benzo(g)chrysene; D004247:DNA