DNA binding of tamoxifen and its analogues: identification of the tamoxifen-DNA adducts in rat liver

DNA binding of tamoxifen and some structurally-related drugs (toremifene, c lomiphene, triparanol and raloxifene) in rat liver was studied using the P- 32-postlabelling method. As only tamoxifen was shown to form high levels of DNA adducts, the identity of these adducts was studied. Recently, we have identified by mass spectroscopy the two main tamoxifen adducts in rat liver DNA as the N-desmethyltamoxifen and tamoxifen adducts of N-2-deoxyguanosin e in which the linkage is through alpha-carbon in the tamoxifen structure. Minor adducts were identical to different diastereomers of alpha-(N-2-deoxy guanosinyl)tamoxifen and of alpha-(N-6-deoxyadenosinyl)tamoxifen. Altogethe r these adducts accounted for at least 95% of adducts formed in vivo, impli cating that the alpha-hydroxylation of the ethyl group is the major activat ion pathway for DNA adducts. (C) 1998 Elsevier Science Ireland Ltd. All rig hts reserved.