Bindal R D, Carlson K E, Reiner G C, Katzenellenbogen J A
School of Chemical Sciences, University of Illinois, Urbana 61801.
J Steroid Biochem. 1987 Oct;28(4):361-70. doi: 10.1016/0022-4731(87)91052-1.
It has been suggested that binding of 11 beta-chloromethyl estradiol (11 beta-CME2) to the estrogen receptor is irreversible, since its complex with receptor fails to undergo exchange with estradiol (E2). To investigate this behavior directly, 11 beta-CME2 was prepared in high specific activity, tritium-labeled form: The binding of [3H]11 beta-CME2 to the estrogen receptor from lamb and rat uterus and MCF-7 human breast cancer cells was shown to be fully reversible; the 11 beta-CME2 complex with receptor, as well as that of a structural analog 11 beta-ethyl estradiol, however, do not dissociate or exchange with [3H]E2 over a 22 h period at 25 degrees C. By competitive or direct binding assays, the affinity of 11 beta-CME2 for the estrogen receptor can be estimated to be as much as 10- to 30-fold higher than that of E2. The complexes of estrogen receptor from MCF-7 cells with [3H]11 beta-CME2 and [3H]E2 show identical velocity sedimentation profiles on sucrose gradients, under conditions when the receptor is either a monomer of a dimer. Because of its very high affinity and unusual dissociation kinetics, [3H]11 beta-CME2 should be a very useful ligand for studies of estrogen receptor dynamics and in the assay of estrogen receptor concentrations in tumors and tissues.
有人提出，11β-氯甲基雌二醇（11β-CME2）与雌激素受体的结合是不可逆的，因为它与受体的复合物不能与雌二醇（E2）进行交换。为了直接研究这种行为，制备了高比活性的氚标记形式的11β-CME2：[3H]11β-CME2与来自羔羊和大鼠子宫以及MCF-7人乳腺癌细胞的雌激素受体的结合被证明是完全可逆的；然而，11β-CME2与受体的复合物以及结构类似物11β-乙基雌二醇的复合物在25℃下22小时内不会与[3H]E2解离或交换。通过竞争性或直接结合测定，11β-CME2对雌激素受体的亲和力估计比E2高10至30倍。在受体为单体或二聚体的条件下，MCF-7细胞的雌激素受体与[3H]11β-CME2和[3H]E2的复合物在蔗糖梯度上显示出相同的速度沉降曲线。由于其非常高的亲和力和不寻常的解离动力学，[3H]11β-CME2应该是研究雌激素受体动力学以及测定肿瘤和组织中雌激素受体浓度的非常有用的配体。
