Catechol estrogen conjugates and DNA adducts in the kidney of male Syrian golden hamsters treated with 4-hydroxyestradiol: Potential biomarkers for estrogen-initiated cancer

Formation of depurinating adducts by reaction of catechol estrogen-3,4-quin ones with DNA was proposed to be a tumor initiating event by estrogens [E.L . Cavalieri et al. (1997) Proc, Natl Acad, Sci, USA, 94, 10937-10942], Unde r estrogenic imbalance, oxidation of catechol estrogens to quinones may com pete with their detoxification by protective enzymes, The quinones formed c an be detoxified by reaction with glutathione (CSH) or can covalently bind to DNA, To provide more support for this hypothesis, we developed a method to identify and quantify GSH, cysteine (Cys) and N-acetylCys conjugates of 4-hydroxyestrogens (4-OHE) in the kidneys of male Syrian hamsters treated w ith 4-hydroxyestradiol (4-OHE2) by intraperitoneal injection, The highest l evel of conjugates was observed 1 fi after treatment, and almost none was d etected after 24 h, Dose-response studies indicated conjugate formation aft er treatment with 0.5 mu mol of 4-OHE2/100 g body weight, and formation inc reased up to a treatment level of 12 mu mol/100 g body weight, GSH, Cys and N-acetylCys conjugates of 4-OHE were identified in the picomole range by h ighperformance liquid chromatography (HPLC) with multichannel electrochemic al detection and confirmed by HPLC/tandem mass spectrometry, Treatment of t issue homogenates with beta -glucuronidase/sulfatase at 37 degreesC for 6 h before extraction resulted in a 12- to 20-fold increase in Cys conjugates from picomole to nanomole levels, Similar enhancement was observed by just incubating the tissue at 37 degreesC for 6 h, Evidence for the 4-OHE-1-N7Gu a depurinating adducts was obtained by mass spectrometry. We conclude that GSH and Cys conjugates of the 4-OHE and the 4-OHE-N7Gua adducts can be util ized as biomarkers to detect estrogenic imbalance and potential susceptibil ity to tumor initiation.