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      Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors alpha and beta.

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          Abstract

          The rat estrogen receptor (ER) exists as two subtypes, ER alpha and ER beta, which differ in the C-terminal ligand binding domain and in the N-terminal transactivation domain. In this study we investigated the messenger RNA expression of both ER subtypes in rat tissues by RT-PCR and compared the ligand binding specificity of the ER subtypes. Saturation ligand binding analysis of in vitro synthesized human ER alpha and rat ER beta protein revealed a single binding component for 16 alpha-iodo-17 beta-estradiol with high affinity [dissociation constant (Kd) = 0.1 nM for ER alpha protein and 0.4 nM for ER beta protein]. Most estrogenic substances or estrogenic antagonists compete with 16 alpha-[125I]iodo-17 beta-estradiol for binding to both ER subtypes in a very similar preference and degree; that is, diethylstilbestrol > hexestrol > dienestrol > 4-OH-tamoxifen > 17 beta-estradiol > coumestrol, ICI-164384 > estrone, 17 alpha-estradiol > nafoxidine, moxestrol > clomifene > estriol, 4-OH-estradiol > tamoxifen, 2-OH-estradiol, 5-androstene-3 beta, 17 beta-diol, genistein for the ER alpha protein and dienestrol > 4-OH-tamoxifen > diethylstilbestrol > hexestrol > coumestrol, ICI-164384 > 17 beta-estradiol > estrone, genistein > estriol > nafoxidine, 5-androstene-3 beta, 17 beta-diol > 17 alpha-estradiol, clomifene, 2-OH-estradiol > 4-OH-estradiol, tamoxifen, moxestrol for the ER beta protein. The rat tissue distribution and/or the relative level of ER alpha and ER beta expression seems to be quite different, i.e. moderate to high expression in uterus, testis, pituitary, ovary, kidney, epididymis, and adrenal for ER alpha and prostate, ovary, lung, bladder, brain, uterus, and testis for ER beta. The described differences between the ER subtypes in relative ligand binding affinity and tissue distribution could contribute to the selective action of ER agonists and antagonists in different tissues.

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          Author and article information

          Journal
          Endocrinology
          Endocrinology
          The Endocrine Society
          0013-7227
          0013-7227
          Mar 1997
          : 138
          : 3
          Affiliations
          [1 ] Center for Biotechnology, Karolinska Institute, Huddinge, Sweden. george.kuiper@cbt.ki.se
          Article
          10.1210/endo.138.3.4979
          9048584
          01da0390-fdc7-499b-9049-7b7d697c0fa4
          History

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