Identification of the major tamoxifen-DNA adducts in rat liver by mass spectroscopy

We present here the first mass spectroscopic (MS) identification of the mai n tamoxifen-induced DNA adducts in rat liver. The two main adducts were iso lated by highperformance liquid chromatography (HPLC) and identified by MS, MS-MS and ultraviolet spectroscopy. Adduct 1 was the N-desmethyltamoxifen- deoxyguanosine adduct in which the a-position of the metabolite N-desmethyl tamoxifen is linked covalently to the amino group of deoxyguanosine, Adduct 2 was confirmed to be the trans isomer of a(N-2-deoxyguanosinyl)tamoxifen, as previously suggested by co-chromatography.