Fishman J H
Endocrinology. 1983 Sep;113(3):1164-6. doi: 10.1210/endo-113-3-1164.
Mature rat uterine cytosol was pretreated with dextran-coated charcoal at 0 C for 2 h. This renders the subsequently formed estradiol-receptor complex thermostable at 37 C and also uncovers antiestrogen binding sites, possibly by removing an endogenous ligand. A sharp distinction is found between tamoxifen and estradiol as receptor ligands in pretreated cytosols in that tamoxifen will inhibit estradiol binding, on incubation at 37 C, only if dithiothreitol (DTT) had been included in the pretreatment solution. The presence of tamoxifen as the sole ligand in cytosol pretreated in the presence of DTT does not protect the estradiol receptor from thermal inactivation and following 37 C incubation tamoxifen is found bound exclusively to antiestrogen binding sites. Incubating the cytosol at 37 C with an equimolar mixture of estradiol and tamoxifen results in a very large increase in receptor-bound estradiol. This effect is attributed to the presence of tamoxifen complexed with antiestrogen sites. Tamoxifen in such equimolar ligand mixture binds to antiestrogen sites and is excluded from receptor sites by the estradiol, whose affinity for these sites is much greater than that of tamoxifen.
将成熟大鼠子宫胞质溶胶在0℃用葡聚糖包被的活性炭预处理2小时。这使得随后形成的雌二醇受体复合物在37℃时具有热稳定性，并且可能通过去除内源性配体而揭示抗雌激素结合位点。在预处理的胞质溶胶中，作为受体配体的他莫昔芬和雌二醇之间存在明显区别，即只有在预处理溶液中加入二硫苏糖醇（DTT）时，他莫昔芬在37℃孵育时才会抑制雌二醇结合。在DTT存在下预处理的胞质溶胶中，仅以他莫昔芬作为唯一配体时，不能保护雌二醇受体免受热失活，并且在37℃孵育后，发现他莫昔芬仅与抗雌激素结合位点结合。将胞质溶胶与雌二醇和他莫昔芬的等摩尔混合物在37℃孵育，会导致受体结合的雌二醇大幅增加。这种效应归因于与抗雌激素位点复合的他莫昔芬的存在。在这种等摩尔配体混合物中，他莫昔芬与抗雌激素位点结合，并被雌二醇排除在受体位点之外，因为雌二醇对这些位点的亲和力远大于他莫昔芬。
