Interaction of 16 alpha-[125I]iodo-estradiol with estrogen receptor and other steroid-binding proteins.
This communication describes the synthesis of 16 alpha-[125I]iodo-estradiol (125I-E2) with specific activities greater than 1000 Ci/mmol (1 Ci = 3.7 x 10(10) becquerels). We show that it binds to the same specific estrogen receptor sites as does [3H]estradiol and that it does so with an affinity that is indistinguishable from that for the latter steroid. This is true for receptor obtained from calf uterus and from a pool of human mammary carcinomas. There is no significant binding of 125 I-E2 to the testosterone-estradiol-binding globulin of human plasma. 125I-E2 also binds tightly to anti-estradiol antibodies raised against estradiol derivatized at carbons 3, 6, and 17. Finally, we show that unlabeled I-E2 is an active estrogen in vivo as demonstrated by its ability to increase uterine weight in ovariectomized rats.
D000818:Animals; D000906:Antibodies; D001681:Biological Assay; D001943:Breast Neoplasms / Q000378:metabolism; D002417:Cattle; D013196:Dihydrotestosterone / Q000378:metabolism; D004958:Estradiol / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D007457:Iodine Radioisotopes; D011863:Radioimmunoassay; D011960:Receptors, Estrogen / Q000378:metabolism*; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*; D014599:Uterus / Q000378:metabolism
D000906:Antibodies; D007457:Iodine Radioisotopes; D011960:Receptors, Estrogen; D012738:Sex Hormone-Binding Globulin; D013196:Dihydrotestosterone; D004958:Estradiol