The in vivo formation and repair of DNA adducts from 1'-hydroxysafrole.

Abstract

1'-Hydroxysafrole is a proximate carcinogenic metabolite of the naturally occurring hepatocarcinogen safrole. Comparison by high-performance liquid chromatography of the nucleoside adducts obtained from hepatic DNA of adult female mice treated with [2',3'-3H]1'-hydroxysafrole with those formed by reaction of deoxyribonucleosides with electrophilic derivatives of 1'-hydroxysafrole indicated that the four in vivo adducts studied were derived from an ester of 1'-hydroxysafrole. Three of the four adducts comigrated with products of the reaction of 1'-acetoxysafrole with deoxyguanosine, whereas the fourth adduct comigrated with the major reaction product of the ester with deoxyadenosine. Analysis of the three deoxyguanosine adducts indicated that all three involve substitution on the 2-amino group of guanine. A sample of ther major adduct prepared from deoxyguanylic acid has been characterized from its NMR spectrum as N2-(trans-isosafrol-3'-yl)-deoxyguanosine, and the deoxyadenosine adduct has been similarly characterized as N6-(trans-isosafrol-3'-yl)-deoxyadenosine. Repair replication was measured in cultured human T98G cells exposed to 1'-acetoxysafrole using the combined 5-bromodeoxyuridine density label and radioisotopic label method. At a concentration of 1 mM 1'-acetoxysafrole, the amount of repair synthesis approached maximum values only about 15% of those obtained after saturating doses of ultraviolet light. Repair patch size distribution was found to be similar in cells treated with ultraviolet light or 1'-acetoxysafrole as determined by the density of repair-labeled DNA relative to that of parental DNA.