Watts C K, Sutherland R L
Mol Pharmacol. 1987 May;31(5):541-51.
Synthetic nonsteroidal antiestrogens are bound intracellularly by two high affinity saturable bindings sites, the estrogen receptor and the microsomal antiestrogen-binding site (AEBS). In order to further define the structural requirements for ligand binding to AEBS from rat liver and the MCF 7 human breast cancer cell line, the relative binding affinities of an extensive series of structurally related ligands were investigated using competitive binding assay techniques. The groups of compounds studied were: analogues of the triphenylethylene antiestrogens, Cl 628 and tamoxifen; analogues of cyclofenil; bibenzyl and stilbene derivatives; analogues of the cytochrome P-450 inhibitor SKF-525A; phenothiazine derivatives; and a series of structurally related compounds with a variety of pharmacological activities. High affinity binding to AEBS required the presence of both a hydrophilic basic aminoether side chain and a hydrophobic aromatic ring structure (di- or tricyclic for maximal affinity). Structural modifications to either influenced binding affinity. Aromatic substitution either raised (CF3) or lowered (OH, OCH3) affinity, apparently by electronic effects transmitted through the benzene nucleus. Side chain structure was the major determinant of binding affinity, but its influence was complex and dependent upon terminal amino group structure, side chain branching and substitution, and tissue source of AEBS. Optimal binding affinity was shown by side chains bearing basic heterocyclic amino terminal groups. Other cellular sites that are known to bind antiestrogens with relatively high affinity include calmodulin, cytochrome P-450, and histamine, dopamine, and muscarinic receptors. Binding studies using a variety of pharmacologically active and radiolabeled ligands selective for these sites, including those for dopamine D1 and D2 receptors ([3H]fluphenazine, [3H]flupenthixol, [3H]spiperone, and [3H]SCH 23390) and histamine H1 receptors ([3H]pyrilamine), demonstrated that several of these compounds interact with AEBS with high affinity. However, the ligand specificity and other binding properties of the AEBS as determined by competitive binding studies and Scatchard analysis show this site to be a molecular entity truly distinct from these other cellular binding sites.
合成非甾体抗雌激素在细胞内与两个高亲和力的可饱和结合位点结合，即雌激素受体和微粒体抗雌激素结合位点（AEBS）。为了进一步明确配体与大鼠肝脏和MCF 7人乳腺癌细胞系中AEBS结合的结构要求，使用竞争性结合分析技术研究了一系列结构相关配体的相对结合亲和力。所研究的化合物组包括：三苯乙烯类抗雌激素Cl 628和他莫昔芬的类似物；环芬尼的类似物；联苄和芪衍生物；细胞色素P - 450抑制剂SKF - 525A的类似物；吩噻嗪衍生物；以及一系列具有多种药理活性的结构相关化合物。与AEBS的高亲和力结合需要同时存在亲水性碱性氨基醚侧链和疏水性芳环结构（二环或三环具有最大亲和力）。对其中任何一个的结构修饰都会影响结合亲和力。芳环取代要么提高（CF3）要么降低（OH、OCH3）亲和力，显然是通过苯核传递的电子效应。侧链结构是结合亲和力的主要决定因素，但其影响很复杂，取决于末端氨基结构、侧链分支和取代以及AEBS的组织来源。带有碱性杂环氨基末端基团的侧链显示出最佳结合亲和力。其他已知以相对高亲和力结合抗雌激素的细胞位点包括钙调蛋白、细胞色素P - 450以及组胺、多巴胺和毒蕈碱受体。使用多种对这些位点具有选择性的药理活性和放射性标记配体进行的结合研究，包括对多巴胺D1和D2受体（[3H]氟奋乃静、[3H]氟哌噻吨、[3H]螺哌隆和[3H]SCH 23390）以及组胺H1受体（[3H]吡拉明）的配体，表明这些化合物中有几种与AEBS具有高亲和力相互作用。然而，通过竞争性结合研究和Scatchard分析确定的AEBS的配体特异性和其他结合特性表明，该位点是一个与这些其他细胞结合位点真正不同的分子实体。
