title: Estrogen 1,2-epoxides or estrogen quinones/semiquinones.
abstract: Metabolic activation of estradiol leading to the formation of catechol estrogens is a prerequisite for its genotoxic activity. Both estrogen-o-quinones/semiquinones and estrogen 1,2-epoxides have been proposed to be responsible for this activity. Incubations of [3H]estradiol and [3H]1 alpha,2 alpha-epoxy-4-estrene-3-one-17 beta-ol (ketotautomer of estradiol 1,2-epoxide) with rat liver microsomal and cytosol preparations were carried out in the presence of SKF 525A, ascorbic acid, glutathione and cysteine. Ascorbic acid decreased binding to proteins and aqueous-soluble fraction with both [3H] estradiol and [3H]epoxyestrenolone in incubations with microsomes but no effect with cytosol fraction. Incubations of microsomes with thiols gave water-soluble metabolites which were characterized as 1(4)-thioether derivatives of 2-hydroxyestradiol and incubations of [3H]epoxyestrenolone with cytosol and thiols gave estradiol-2-thioether. Incubations with ascorbic acid and thiols resulted in decreased formation of water-soluble metabolites in microsomal incubations but not in cytosol incubations. These studies indicate that the major pathway for irreversible binding of estrogens to macromolecules involves estrogen-o-quinones/semiquinones and not estrogen 1, 2-epoxide.
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004852:Epoxy Compounds / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism; D004967:Estrogens / Q000378:metabolism*; D002393:Estrogens, Catechol / Q000096:biosynthesis; D008099:Liver / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism; D009277:Nandrolone / Q000031:analogs & derivatives / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D013237:Stereoisomerism
chemical_list: D004852:Epoxy Compounds; D004967:Estrogens; D002393:Estrogens, Catechol; C047127:1,2-epoxyestrenolone; D004958:Estradiol; D009277:Nandrolone; D003545:Cysteine; D001205:Ascorbic Acid