Tinnanooru Pushpalatha, Dang Vu Hoang, Nguyen Thi Hoa, Lee Geun-Shik, Choi Kyung-Chul, Jeung Eui-Bae
Laboratory of Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk, Republic of Korea.
Mol Cell Endocrinol. 2008 Mar 26;285(1-2):26-33. doi: 10.1016/j.mce.2008.01.011. Epub 2008 Jan 31.
Estrogen (E2; estradiol) plays a key role in the regulation of many pituitary hormones. It exerts its effects by binding to the intracellular estrogen receptor (ER), which then functions as a transcription factor. Although E2 has been shown to regulate calbindin-D(9k) (CaBP-9k) in the female reproductive system of rodents, the effects of E2 on the regulation of CaBP-9k in male rats remain to be elucidated. To investigate E2-induced regulation of the pituitary CaBP-9k gene, immature male rats were injected with E2 daily for 3 consecutive days with a dose of 40 microg/kg body weight (BW). The expression levels of CaBP-9k mRNA and protein were analyzed by RT-PCR and Western blot analysis, respectively, in the absence and presence of ICI 182,780 (ICI), an E2 antagonist. In addition, the tissue localization of CaBP-9k was determined by immunohistochemistry. CaBP-9k was localized in the cytoplasm of a specific cell type (acidophils) in the anterior lobe of the pituitary gland and highly expressed in the intermediate lobe. Exposure to E2 increased the number of cells that stained positive for CaBP-9k. To determine which ER subtype is involved in CaBP-9k regulation in the pituitary, the immature rats were treated with propyl pyrazole triol (PPT, an ERalpha-selective ligand) or diarylpropionitrile (DPN, an ERbeta-selective ligand) for 3 days. Pituitary CaBP-9k expression was mainly mediated by PPT in immature male rats, whereas no significant alteration of pituitary CaBP-9k gene expression was observed after DPN treatment. In addition, the estrogenicity of PPT in the induction of CaBP-9k expression was completely blocked by an estrogen antagonist, ICI, indicating that pituitary CaBP-9k expression is solely induced by ERalpha. Taken together, these results suggest that pituitary CaBP-9k is induced by E2 in male rats and its expression is predominantly regulated by ERalpha, but not ERbeta.
雌激素（E2；雌二醇）在多种垂体激素的调节中起关键作用。它通过与细胞内雌激素受体（ER）结合发挥作用，然后该受体作为转录因子发挥功能。尽管已表明E2可调节啮齿动物雌性生殖系统中的钙结合蛋白-D（9k）（CaBP-9k），但E2对雄性大鼠CaBP-9k调节的影响仍有待阐明。为了研究E2诱导的垂体CaBP-9k基因调节，对未成熟雄性大鼠连续3天每天注射剂量为40微克/千克体重（BW）的E2。在存在和不存在E2拮抗剂ICI 182,780（ICI）的情况下，分别通过逆转录聚合酶链反应（RT-PCR）和蛋白质印迹分析来分析CaBP-9k mRNA和蛋白质的表达水平。此外，通过免疫组织化学确定CaBP-9k的组织定位。CaBP-9k定位于垂体前叶特定细胞类型（嗜酸性细胞）的细胞质中，并在中间叶中高度表达。暴露于E2增加了CaBP-9k染色阳性的细胞数量。为了确定哪种ER亚型参与垂体中CaBP-9k的调节，对未成熟大鼠用丙基吡唑三醇（PPT，一种ERα选择性配体）或二芳基丙腈（DPN，一种ERβ选择性配体）处理3天。在未成熟雄性大鼠中，垂体CaBP-9k表达主要由PPT介导，而在DPN处理后未观察到垂体CaBP-9k基因表达的显著改变。此外，雌激素拮抗剂ICI完全阻断了PPT诱导CaBP-9k表达的雌激素活性，表明垂体CaBP-9k表达仅由ERα诱导。综上所述，这些结果表明垂体CaBP-9k在雄性大鼠中由E2诱导，其表达主要由ERα调节，而非ERβ。
