High affinity binding of anti-oestrogen to the chick liver nuclear oestrogen receptor.
High affinity binding of anti-oestrogen to the chick liver nuclear oestrogen receptor.
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抗雌激素与鸡肝核雌激素受体高亲和力结合。
DOI：
10.1042/bj2060387
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
V. Jordan
中科院分区：
文献类型：
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作者：
C. Lazier;V. Jordan
他莫昔芬是鸡肝脏特异性雌激素诱导的蛋黄蛋白合成的有效抑制剂。经雌激素处理的雏鸡肝核盐提取物中雌二醇受体的K(d)值为0.7+/-0.2nm。他莫昔芬及其代谢物单羟他莫昔芬在K(i)值分别为2.6和0.1nm时竞争与盐溶性核受体的结合。当使用完整细胞核进行实验时，抗雌激素对[(3)H]雌二醇结合的抑制作用要小得多。在盐提取物和完整细胞核中，未标记雌二醇与受体结合的[(3)H]雌二醇的竞争是相同的。这表明完整的细胞核含有结合抗雌激素的成分，但不含雌二醇。虽然他莫昔芬和去甲基他莫昔芬很容易与盐溶性核雌激素受体分离，但单羟基他莫昔芬在通常用于交换试验的条件下不会分离。一种改进的测定方法被开发出来，其中60-70%的单羟基他莫昔芬结合位点被证明可以被[(3)H]雌二醇交换。可溶性受体制剂首先在1.7%木炭悬浮液中37℃孵育15min，然后测定特异性雌二醇结合。该技术用于研究他莫昔芬和单羟基他莫昔芬对体内核雌激素受体浓度的影响。尽管它们对受体的结合亲和力相差30倍，但两种抗雌激素增加核受体水平的程度大致相同。当与雌二醇一起给药时，两种化合物对雌激素诱导的核受体增加具有相同的部分抑制作用。这些数据与他莫昔芬在与肝脏雌激素受体结合前的代谢羟基化一致。
Tamoxifen is a potent inhibitor of specific oestrogen-induced yolk protein synthesis by chicken liver. The oestradiol receptor in salt extracts of liver nuclei from oestrogen-treated chicks has a K(d) for oestradiol of 0.7+/-0.2nm. Tamoxifen and its metabolite, monohydroxytamoxifen, compete for binding to the salt-soluble nuclear receptor with K(i) values of 2.6 and 0.1nm respectively. The anti-oestrogens show much less inhibition of [(3)H]oestradiol binding when assays are carried out using intact nuclei. The competition by unlabelled oestradiol for [(3)H]oestradiol binding to receptor is identical in both salt extracts and intact nuclei. This suggests that intact nuclei contain components which bind anti-oestrogens, but not oestradiol. While tamoxifen and desmethyltamoxifen will readily dissociate from the salt-soluble nuclear oestrogen receptor, monohydroxytamoxifen does not dissociate under the conditions generally used for exchange assays. A modified assay was developed in which 60-70% of monohydroxytamoxifen-bound sites were shown to be exchangeable for [(3)H]oestradiol. Soluble receptor preparations were first incubated in a 1.7% charcoal suspension at 37 degrees C for 15min before assay of specific oestradiol binding. This technique was used in examining the effects of tamoxifen and monohydroxytamoxifen given in vivo on the nuclear oestrogen receptor concentration. Despite their 30-fold difference in binding affinity for the receptor, both anti-oestrogens increase nuclear receptor levels to about the same degree. When given with oestradiol, both compounds have the same apparent partial inhibitory effect on the oestrogen-induced increase in nuclear receptor. These data are consistent with the metabolic hydroxylation of tamoxifen before binding to the hepatic oestrogen receptor.