32P-postlabelling analysis of dibenz[a,j]acridine-DNA adducts in mice: identification of proximate metabolites.
N-Heterocyclic polynuclear aromatics are widely-occurring environmental pollutants formed during the pyrolysis of nitrogen-containing organic chemicals. Dibenz[a,j]acridine (DBA), a member of this class, has been shown to be a skin carcinogen in mice. We undertook studies to determine the organ distribution of DBA-DNA adducts and to identify the DBA metabolites which lead to the formation of carcinogen-DNA adducts in vivo. DBA and its metabolites, trans-DBA-1,2-dihydrodiol (DBA-1,2-DHD) trans-DBA-3,4-dihydrodiol (DBA-3,4-DHD) and trans-DBA-5,6-dihydrodiol (DBA-5,6-DHD), were topically applied on mice. DNA was isolated using enzyme-solvent extraction methods, and analyzed for carcinogen-DNA adducts using 32P-postlabelling. In skin, DBA produced two distinct adducts (Adducts 1 and 2). The same two adducts were seen when DBA-3,4-DHD was applied. In addition, the total adduct level elicited by DBA-3,4-DHD was twice that of the parent compound. Two adducts (Adducts 3 and 4) were also seen in mouse skin when DBA-5,6-DHD was applied, but these differed chromatographically from adducts seen with DBA. However, when DBA-3,4-DHD was applied and analyzed using sensitive nuclease P1 32P-postlabelling, all four adducts could be detected. These results suggest that the major route of DBA activation to DNA-binding species in skin is through formation of DBA-3,4-DHD and subsequent metabolism of this compound to a bay-region diol-epoxide. However, we postulate that another activation pathway may proceed through a bis-dihydrodiol-epoxide.
Talaska
G
G
Department of Environmental Health, University of Cincinnati, OH 45267-0056.
Roh
J
J
Schamer
M
M
Reilman
R
R
Xue
W
W
Warshawsky
D
D
D000166:Acridines / Q000378:metabolism* / Q000633:toxicity*; D000287:Administration, Topical; D000818:Animals; D001345:Autoradiography; D002273:Carcinogens / Q000378:metabolism* / Q000633:toxicity*; D004247:DNA / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism*; D018736:DNA Adducts / Q000096:biosynthesis*; D005260:Female; D007553:Isotope Labeling; D051379:Mice; D008813:Mice, Inbred ICR; D010761:Phosphorus Radioisotopes; D012680:Sensitivity and Specificity; D012867:Skin / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism
D000166:Acridines; D002273:Carcinogens; D018736:DNA Adducts; D010761:Phosphorus Radioisotopes; C022289:dibenzacridine; D004247:DNA