Estrogen 1,2-epoxides or estrogen quinones/semiquinones

Yusuf J. Abul-Hajj

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12 Scopus citations


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]1α,2α-epoxy-4-estrene-3one-17β-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 cystosol 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.

Original languageEnglish (US)
Pages (from-to)1078-1085
Number of pages8
JournalBiochemical and Biophysical Research Communications
Issue number3
StatePublished - Dec 31 1985

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