The formation and persistence of benzo(<i>a</i>)pyrene metabolite‐deoxyribonucleoside adducts in rat skin <i>in vivo</i>

Abstract

Abstract The extent of reaction of benzo( a )pyrene with DNA and the formation of benzo( a )pyrene‐deoxyribonucleoside adducts in the skins of male Wistar rats were investigated. Following topical application of benzo( a )pyrene (200 nmoles), binding reached a maximum of 0,74 pmoles/mg DNA, 12 h after treatment, and remained high up to 48 h after treatment. Hydrolysis of the DNA and analysis of the deoxyribonucleoside adducts by HPLC revealed several products. The major adduct, C, (27‐40% of the total adducts), co‐chromatographed with deoxyribonucleoside adducts formed by reaction of (±)7β, 8α‐dihyroxy‐9α, 10α‐epoxy‐7,8,9,10‐tetrahydrobenzo( a )pyrene (anti BPDE) with DNA, whilst product B, (19–23% of the total adducts), also formed in significant amounts, co‐chromatographed with a further metabolite of 9‐hydroxybenzo( a )pyrene bound to an as yet undertermined base in the DNA. Smaller amounts of other deoxyribonucleoside adducts, D and I, were also observed and co‐chromatographed with marker compounds derived from reaction of anti BPDE with deoxyadenosine and (±)7β, 8α‐dihydroxy‐9β, 10β‐epoxy‐7,8,9,10‐tetrahydrobenzo( a )pyrene ( Syn BPDE) with DNA respectively. There was no evidence for preferential removal of any of the four adducts (B, C, D and I) during the 48 h after treatment with benzo( a )pyrene. The relative resistance of rat skin, compared with mouse skin, to benzo( a )pyrene‐induced skin carcinogenesis may be due in part to a lower extent of binding of benzo( a )pyrene to DNA, and a smaller percentage of both methanol‐soluble hydrocarbon‐deoxyribonucleoside adducts and of adducts derived from the putative ultimate carcinogen, BPDE.