title: In vitro and in vivo studies on oxygen free radical and DNA adduct formation in rat lung and liver during benzo[a]pyrene metabolism.
abstract: Reactive oxygen species (ROS), possibly produced during the metabolic conversion of benzo(a)pyrene (B[a]P), could be involved in B[a]P-induced genotoxicity and, eventually, carcinogenicity. Therefore, ROS formation by rat lung and liver microsomes was studied in vitro by electron spin resonance (ESR/EPR) spectrometry. B[a]P-mediated generation of ROS was detected in incubations with rat lung, but not with liver microsomes. Inhibition of cytochrome P450 (CYP450) by the non isoform-specific inhibitor SKF-525A resulted in a complete inhibition of B[a]P-dependent ROS formation, whereas ROS formation was not affected by inhibition of prostaglandin H synthase by indomethacin. Subsequently, bulky DNA adduct formation and 8-oxo-dG levels after a single oral dose of B[a]P were examined in vivo in rat lung and liver, in combination with urinary excretion of 8-oxodG. B[a]P exposure resulted in increased urinary 8-oxo-dG levels. On the contrary, 8-oxo-dG levels decreased in liver and lung after B[a]P exposure. Bulky DNA adducts reached higher levels and were more persistent in rat lung than in liver. These results indicate that ROS are generated during the CYP450 dependent metabolism of B[a]P, particularly in the rat lung, but this does not necessarily result in increased levels of oxidative DNA damage in vivo, possibly by induction of DNA repair mechanisms.
authors.affiliation: Department of Health Risk Analysis and Toxicology, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands.
authors.forename: Jacob J
authors.initials: JJ
authors.lastname: Briedé
authors.forename: Roger W L
authors.initials: RW
authors.lastname: Godschalk
authors.forename: Marijn T G
authors.initials: MT
authors.lastname: Emans
authors.forename: Theo M C M
authors.initials: TM
authors.lastname: De Kok
authors.forename: Ebienus
authors.initials: E
authors.lastname: Van Agen
authors.forename: Jan
authors.initials: J
authors.lastname: Van Maanen
authors.forename: Frederik-Jan
authors.initials: FJ
authors.lastname: Van Schooten
authors.forename: Jos C S
authors.initials: JC
authors.lastname: Kleinjans
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D001564:Benzo(a)pyrene / Q000633:toxicity*; D002478:Cells, Cultured; D018736:DNA Adducts / Q000096:biosynthesis*; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000032:analysis / Q000652:urine; D004578:Electron Spin Resonance Spectroscopy; D008099:Liver / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D008168:Lung / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D018736:DNA Adducts; D017382:Reactive Oxygen Species; C056612:benzo(a)pyrene-DNA adduct; D001564:Benzo(a)pyrene; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine