title: Effects of sulfhydryl reagents on uterine nuclear estrogen receptors labeled by in vitro exchange with [3H]estradiol or [3H]4-hydroxytamoxifen.
abstract: We have attempted to convert 4 S uterine nuclear estrogen receptors obtained after in vitro labeling with [3H]antiestrogens to 3 S, the form observed after in vitro exchange with [3H]estradiol, in order to examine the possible relationship between these forms. Treatment of nuclear extracts labeled with the high affinity antiestrogen, [3H]4-hydroxytamoxifen, with a variety of nucleases, phosphatases, or proteases either had no effect on the 4 S antiestrogen-receptor complex or led to loss of ligand binding. The sulfhydryl reducing agents, cysteine or reduced glutathione, on the other hand, brought about conversion of 4 S estrogen receptors to components sedimenting at about 3 S. Conversely, when oxidized glutathione was included in all buffers used for preparation and labeling of nuclear estrogen receptors with [3H]estradiol, more rapidly sedimenting (approximately 4.6 S) forms of estrogen-receptor complex predominated. Cysteine still effected the 4 S to 3 S conversion when nuclear estrogen receptors, partially purified by sucrose gradient centrifugation, were used as substrate, suggesting a direct action of the sulfhydryl reagents on receptor molecules. From these results we propose that nuclear estrogen and antiestrogen-receptor complexes may differ in conformation such that the former may be more sensitive to the action of an endogenous reducing agent which contributes to formation of 3 S [3H]estradiol-receptor complexes.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003545:Cysteine / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism; D005260:Female; D005978:Glutathione / Q000031:analogs & derivatives / Q000494:pharmacology; D019803:Glutathione Disulfide; D066298:In Vitro Techniques; D051381:Rats; D011960:Receptors, Estrogen / Q000187:drug effects* / Q000378:metabolism; D013439:Sulfhydryl Reagents / Q000494:pharmacology*; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000378:metabolism; D014599:Uterus / Q000378:metabolism
chemical_list: D011960:Receptors, Estrogen; D013439:Sulfhydryl Reagents; D013629:Tamoxifen; C016601:afimoxifene; D004958:Estradiol; D005978:Glutathione; D003545:Cysteine; D019803:Glutathione Disulfide