Inactivation of the uterine estrogen receptor binding of estradiol during P-450 catalyzed metabolism of chlorotrianisene (TACE). Speculation that TACE antiestrogenic activity involves covalent binding to the estrogen receptor.
Chlorotrianisene (TACE) exhibits in vitro little or no binding to the uterine estrogen receptor (ER) but demonstrates potent estrogenic activity in vivo, indicating that TACE is a proestrogen/proantiestrogen. Our earlier studies demonstrated that the incubation of TACE with rat liver microsomes and NADPH generates a reactive intermediate (T*) which binds covalently to proteins. The current study examined the possibility that T* may inactivate the uterine ER. The incubation of TACE with rat liver microsomes and NADPH in the presence of rat uteri, under conditions which generate T*, markedly decreased the binding capacity of the ER for [3H]estradiol (E2). The evidence indicates that ER inactivation was probably due to irreversible (covalent) binding of T* to the E2 binding site. The possibility that the antiestrogenic action of TACE and of other triphenylethylenes involves such a novel mechanism is discussed.
Kupfer
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Worcester Foundation for Experimental Biology, Shrewsbury, MA 01545.
Bulger
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D000818:Animals; D002741:Chlorotrianisene / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism*; D004965:Estrogen Antagonists; D005260:Female; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D011355:Prodrugs; D051381:Rats; D011919:Rats, Inbred Strains; D011960:Receptors, Estrogen / Q000378:metabolism*; D014599:Uterus / Q000378:metabolism*
D004965:Estrogen Antagonists; D011355:Prodrugs; D011960:Receptors, Estrogen; D004958:Estradiol; D009249:NADP; D002741:Chlorotrianisene; D003577:Cytochrome P-450 Enzyme System