Different interaction of estradiol and antiestrogens with the estrogen receptor of rat uterus.
Cytosoluble estradiol-receptor (ER) complexes obtained from uteri of castrated rats show a 4.3 S sedimentation coefficient when analysed by sucrose gradient in high salt buffer both in the absence and presence of 0.1 M ammonium thiocyanate. After incubation with nuclei, the complexes sediment at 4.3 S and at 3.2 S, in the absence and presence of 0.1 M ammonium thiocyanate respectively. This structural modification of ER is also confirmed by gel filtration analysis. In similar conditions hydroxytamoxifen-ER complexes apparently do not undergo such a modification. However, increasing the molarity of the chaotropic ion up to 0.5 M shows that, in fact, the modification occurs. Sodium dodecylsulfate-polyacrylamide gel electrophoresis analysis of covalently linked tamoxifen aziridine-ER 'complexes' confirms that the nuclear treatment reduces the apparent molecular weight of ER from 62 000 to 47 000. These data demonstrate that, in vitro, nuclear ER is cleaved into a smaller molecular form and that the receptor fragments can be held together by the triphenylethylene antiestrogen hydroxytamoxifen.
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D004958:Estradiol / Q000378:metabolism*; D004965:Estrogen Antagonists / Q000378:metabolism*; D005260:Female; D008970:Molecular Weight; D051381:Rats; D011919:Rats, Inbred Strains; D011960:Receptors, Estrogen / Q000378:metabolism*; D013629:Tamoxifen / Q000378:metabolism; D014599:Uterus / Q000378:metabolism*
D004965:Estrogen Antagonists; D011960:Receptors, Estrogen; D013629:Tamoxifen; D004958:Estradiol