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Estrogens induce tumors in laboratory animals and have been associated with breast and uterine cancers in humans. In relation to the role of estrogens in the induction of cancer, we examine formation of DNA adducts by reactive electrophilic estrogen metabolites, formation of reactive oxygen species by estrogens and the resulting indirect DNA damage by these(More)
Natural and synthetic estrogens elicit normal hormonal responses in concentrations in a clearly defined yet low range. At elevated doses, metabolic reactions of the phenolic moiety, while harmless at low levels, may become the predominant biochemical activity and may exert deleterious effects. These metabolic pathways, such as i) oxidation of estrogens to(More)
Estrogen administration to rodents results in various types of DNA damage and ultimately leads to tumors in estrogen-responsive tissues. Yet these hormones have been classified as nonmutagenic, because they did not induce mutations in classical bacterial and mammalian mutation assays. In this review, we have discussed the induction by estrogens of DNA and(More)
Cytochrome P-450-mediated redox cycling between the synthetic estrogen diethylstilbestrol (DES) and diethylstilbestrol-4',4"-quinone (DES Q) has previously been demonstrated. Cytochrome P-450 reductase catalyzes the reduction of DES Q presumably via a semiquinone formed by one-electron reduction. A reducing action of NAD(P)H quinone reductase (EC 1.6.99.2)(More)
The role of thiols (nonprotein and protein) in the metabolic activation of phenytoin was examined. In vitro phenytoin covalent binding and metabolite formation were determined in hepatic microsomes from A/J mice. Covalent binding of a phenytoin-reactive intermediate to microsomal protein was linear with respect to time, protein concentration and phenytoin(More)
Data are reported demonstrating a role for glutathione and age in the metabolic activation of phenytoin to a reactive metabolite. The in vitro liver microsomal covalent binding of [14C]-phenytoin (DPH) was examined in mice and rats. After incubation with 25-300 microM DPH, covalent binding was dose dependent and linear with time. Incubation in an atmosphere(More)
Target organ-specific estrogen-induced DNA adducts were previously shown to precede renal carcinogenesis in Syrian hamsters. Because estrogens induced these DNA modifications, but were not part of the adduct structure, free radical activation of endogenous electrophiles was postulated as a mechanism of tumor induction by estrogens. In the present study, the(More)
The generation of free radicals by microsome-mediated redox cycling between catechol estrogens or diethylstilbestrol and their corresponding quinones has previously been demonstrated in vitro. However, the reaction of free radicals with DNA has not yet been detected in animals treated with estrogen and is the subject of this investigation. The reaction of(More)
Dietary supplementation of vitamin C to diethylstilbestrol (DES)- or estradiol-treated male Syrian hamsters is known to inhibit renal carcinogenesis by approximately 50%. To elucidate the mechanism of inhibition, the influence of administration of vitamin C on a series of previously described biochemical markers of kidney carcinogenesis was investigated.(More)
Curcumin is a major chemical constituent of turmeric normally eaten by humans. 12-O-Tetradecanoyl phorbol-13-acetate (TPA) is a strong promoter of chemically induced skin cancer. The exact mechanism by which TPA promotes skin cancer is not clear. However, it is known that TPA elevates the expression of oncogenes involved in cell proliferation. Recently, it(More)