Zhou Y, Chorich L P, Mahesh V B, Ogle T F
Department of Physiology and Endocrinology, Medical College of Georgia, Augusta 30912-3000.
J Steroid Biochem Mol Biol. 1993 Dec;46(6):687-98. doi: 10.1016/0960-0760(93)90310-s.
The objective of this study was to examine the mechanisms of estrogen receptor (ER) processing and replenishment in the uterus of ovariectomized rats after estradiol and progesterone treatment. Uterine ER binding activity, ER protein and ER mRNA were measured by receptor binding exchange assay, Western blot and slot blot, respectively. The regulation of ER levels in rat uterus by estradiol and progesterone was very dramatic. Changes in ER protein were faithfully reflected by changes in binding activity. Estradiol caused receptor "processing" within 4 h of administration followed by recovery or "replenishment" of ER levels to the initial level by 20 h. The term "processing" has previously been used to describe the loss of ER binding activity in the early phase of estradiol-action, but it was never clear whether the ligand binding site was inactivated by processing or if the receptor molecule actually disappeared. This study shows that receptor "processing" constitutes disappearance of receptor protein and the later "replenishment" phase represents new ER protein rather than recycling of "processed" receptor. Progesterone-action, on the other hand, influenced only the "replenishment" phase by blocking recovery of ER protein. ER mRNA was suppressed by estradiol at 8 h, after the receptor was "processed" and "replenishment" already initiated. Progesterone, on the other hand, did not alter the steady state level of the message. Other mechanisms, such as regulation of translation rate of existing mRNA and changes in the rate of degradation of ER proteins are more likely involved in acute regulation of ER by these ovarian steroid hormones.
本研究的目的是检测雌二醇和孕酮处理后去卵巢大鼠子宫中雌激素受体（ER）加工和补充的机制。分别通过受体结合交换分析、蛋白质免疫印迹法和狭缝印迹法测定子宫ER结合活性、ER蛋白和ER mRNA。雌二醇和孕酮对大鼠子宫中ER水平的调节作用非常显著。结合活性的变化如实反映了ER蛋白的变化。雌二醇给药后4小时内引起受体“加工”，随后到20小时时ER水平恢复或“补充”至初始水平。术语“加工”此前用于描述雌二醇作用早期ER结合活性的丧失，但尚不清楚配体结合位点是通过加工而失活，还是受体分子实际消失。本研究表明，受体“加工”构成受体蛋白的消失，而后期的“补充”阶段代表新的ER蛋白，而非“加工”受体的再循环。另一方面，孕酮的作用仅通过阻断ER蛋白的恢复来影响“补充”阶段。在受体“加工”和“补充”已经开始后，雌二醇在8小时时抑制ER mRNA。另一方面，孕酮并未改变该信息的稳态水平。这些卵巢甾体激素对ER的急性调节更可能涉及其他机制，如对现有mRNA翻译速率的调节和ER蛋白降解速率的变化。
