Shyamala G, Singh R K, Ruh M F, Ruh T S
Endocrinology. 1986 Aug;119(2):819-26. doi: 10.1210/endo-119-2-819.
Mammary glands from nulliparous mice are responsive to estradiol, whereas mammary glands from lactating mice are unresponsive, despite the presence of high concentrations of estrogen receptors. This study examined the relation between mammary estrogenic sensitivity and ability of mammary estrogen receptors to bind to intact chromatin as well as to partially deproteinized chromatin. Mammary chromatin was prepared from nulliparous and lactating mice, linked covalently to cellulose and deproteinized sequentially by 0-8 M guanidine chloride (Gdn X HCl). The binding of receptors to these various chromatin preparations was determined using partially purified [3H]estradiol-receptor complexes ([3H]ER) obtained by fractionation on diethylaminoethyl cellulose columns. The binding pattern of [3H]ER from nulliparous mice to chromatin fractions from either nulliparous or lactating mice revealed maximal binding activity with chromatin previously extracted with 4-6 M Gdn X HCl. Binding was of high affinity [dissociation constant (Kd) 3.6 X 10(-10) M], saturable and steroid receptor and species specific. However, mammary [3H]ER preparations from lactating mice bound poorly to intact chromatin as well as to the Gdn X HCl extracted chromatin fractions isolated from either mammary gland of nulliparous or lactating mice. In mixing experiments the estrogen receptor preparation from lactating mice decreased substantially the binding activity of [3H]ER from nulliparous mice to chromatin suggesting the presence of an inhibiting factor. Thus, these studies reveal that the unresponsiveness of lactating mammary glands to estradiol coexists with the inability of estrogen receptors from lactating mice to interact with specific high affinity sites on mammary chromatin and also that this impeded interaction of estrogen receptors with chromatin may be due to some inhibitor(s) present in the cytosol of lactating mammary glands.
未生育小鼠的乳腺对雌二醇有反应，而泌乳小鼠的乳腺尽管存在高浓度的雌激素受体，但却无反应。本研究检测了乳腺雌激素敏感性与乳腺雌激素受体结合完整染色质以及部分脱蛋白染色质能力之间的关系。从未生育和泌乳小鼠制备乳腺染色质，将其与纤维素共价连接，并依次用0 - 8M盐酸胍（Gdn X HCl）进行脱蛋白处理。使用通过二乙氨基乙基纤维素柱分级分离获得的部分纯化的[³H]雌二醇 - 受体复合物（[³H]ER）来测定受体与这些不同染色质制剂的结合。未生育小鼠的[³H]ER与未生育或泌乳小鼠的染色质组分的结合模式显示，与先前用4 - 6M Gdn X HCl提取的染色质具有最大结合活性。结合具有高亲和力[解离常数（Kd）3.6×10⁻¹⁰M]，具有饱和性、类固醇受体和物种特异性。然而，泌乳小鼠的乳腺[³H]ER制剂与完整染色质以及从未生育或泌乳小鼠乳腺分离的Gdn X HCl提取的染色质组分结合较差。在混合实验中，泌乳小鼠的雌激素受体制剂显著降低了未生育小鼠的[³H]ER与染色质的结合活性，提示存在抑制因子。因此，这些研究表明，泌乳乳腺对雌二醇无反应与泌乳小鼠的雌激素受体无法与乳腺染色质上的特定高亲和力位点相互作用同时存在，并且雌激素受体与染色质之间这种受阻的相互作用可能是由于泌乳乳腺细胞质中存在的某些抑制剂所致。
