The metabolic activation of dibenz[a,h]anthracene in mouse skin examined by ³²P-postlabelling: minor contribution of the 3,4-diol 1,2-oxides to DNA binding

Abstract

Dibenz[a,h]anthracene (DB[a,h]A) and the related 3,4-diol and anti- and syn-3,4-diol 1,2-oxides were applied to the shaved dorsal skin of groups of four C57Bl/CB1 mice. Twenty-four hours later the mice were killed, DNA isolated from the treated skin, hydrolysed and examined for the presence of aromatic adducts using the nuclease P1 modification of the 32P-postlabelling technique. Autoradiography of the maps obtained by chromatography on polyethyleneimine-cellulose plates showed that six DNA adduct spots that were derived from DB[a,h]A were also present in the DNA of skin treated with the DBA 3,4-diol and that, whilst four of these adduct spots were also seen in maps prepared from the DNA of skin treated with the anti-3,4-diol-1,2-oxide, they were not present in DNA from skin to which the syn-isomer had been applied. The identity of these adduct spots was confirmed by their coincidence when mixtures of different DNA hydrolysates were chromatographed together. Quantitatively, the highest levels of mouse skin modification were obtained with the diol-epoxides and the lowest with DB[a,h]A. The results suggest that most of the DNA adducts formed in DB[a,h]A-treated mouse skin arise through metabolism of the hydrocarbon to the related 3,4-diol and that some may be formed following the conversion of this diol to the bay-region anti-3,4-diol-1,2-oxide.

The molecular etiology and prevention of estrogen-initiated cancers

“…This symmetrical compound can form not only the bay-region 3,4-diol-1,2-epoxide, but also the 3,4:10,11-bis-diol-1,2-epoxide (Carmichael et al, 1993; Fuchs et al, 1993a, 1993b). When the metabolism, mutagenicity, carcinogenicity and formation of DNA adducts of this compound were studied, all of the results indicated that it is activated via the diol epoxide pathway (Fuchs et al, 1993a, 1993b; Lecoq et al, 1991, 1992; Platt, et al, 1990). One study suggests that the 3,4:10,11-bis-diol-1,2-epoxide is the most important for the carcinogenicity of this compound (Carmichael et al, 1993).…”

Bisdihydrodiols, rather than dihydrodiol oxides, are the principal microsomal metabolites of tumorigenic trans-3,4-dihydroxy-3,4-dihydrodibenz[a,h]anthracene

“…Thus the postulated reactivity of the ultimate mutagens of the three bisdihydrodiols was confirmed by the extent of DNA binding in mouse skin (42), which rose from no detectable binding in the case of DBA-3,4:12,13-bisdihydrodiol to weak binding in the case of DBA-3,4:8,9-bisdihydrodiol, reaching its highest value in the case of DBA-3,4:10,11bisdihydrodiol. Furthermore, DBA and DBA-3,4-dihydrodiol yielded the same pattern of DNA adducts when incubated with rat liver microsomes (38,39) or when applied to mouse skin in vivo (40), demonstrating anew the biological significance of the M-region dihydrodiol of DBA as precursor of its genotoxic metabolite(s). In both metabolizing systems DNA adducts based on bay-region dihydrodiol oxides were detected (38)(39)(40) and could be characterized ( 39), yet, especially in vivo, their amount was surpassed by more polar adducts (40).…”

“…Furthermore, DBA and DBA-3,4-dihydrodiol yielded the same pattern of DNA adducts when incubated with rat liver microsomes (38,39) or when applied to mouse skin in vivo (40), demonstrating anew the biological significance of the M-region dihydrodiol of DBA as precursor of its genotoxic metabolite(s). In both metabolizing systems DNA adducts based on bay-region dihydrodiol oxides were detected (38)(39)(40) and could be characterized ( 39), yet, especially in vivo, their amount was surpassed by more polar adducts (40). Remarkably, this could be shown not only with mouse skin (40) but also with human skin in culture (41).…”

“…Therefore, it will be interesting to determine the stereoselectivity in the metabolic conversion of enantiomeric DBA-3,4-dihydrodiol and to eluciate the role of the stereoisomers of the bisdihydrodiols in the genotoxicity of DBA. The relevance of the metabolic pathways elucidated in this study for the genotoxic activity of DBA has been furthermore ascertained by determination of the DNA binding in vitro (36,38,39) and in vivo (40)(41)(42). Thus the postulated reactivity of the ultimate mutagens of the three bisdihydrodiols was confirmed by the extent of DNA binding in mouse skin (42), which rose from no detectable binding in the case of DBA-3,4:12,13-bisdihydrodiol to weak binding in the case of DBA-3,4:8,9-bisdihydrodiol, reaching its highest value in the case of DBA-3,4:10,11bisdihydrodiol.…”

Presencia de hidrocarburos aromáticos policíclicos en puertos argentinos y península Antártica: marcación con I-131 y ensayos de descontaminación

“…Una variedad de métodos físicos fueron descriptos para la detección de aductos, incluyendo espectroscopia de fluorescencia de línea angosta (fluorescence line narrowing spectroscopy), espectroscopia de fluorescencia sincrónica (synchronous fluorescence spectroscopy) y algunos procedimientos especializados de cromatografía gaseosaespectrometría de masa (CG-EM) (Weston, 1993). Los métodos físicos combinan alta sensibilidad sin requerir una anterior radiomarcación de los carcinógenos o de sus aductos, y pueden ser no-destructivos (Lecoq et al, 1991(Lecoq et al, , 1992Carmichael et al, 1993;Nesnow et al, 1994;Hecht et al, 1995).…”