Yamada M, Monden T, Satoh T, Iizuka M, Murakami M, Iriuchijima T, Mori M
First Department of Internal Medicine, Gunma University School of Medicine, Japan.
Biochem Biophys Res Commun. 1992 Apr 15;184(1):367-72. doi: 10.1016/0006-291x(92)91202-2.
We studied the effect of thyroid status on thyrotropin-releasing hormone receptor (TRH-R) mRNA levels both in vivo and in vitro (GH3 cells) using a cloned rat TRH-R cDNA by RT-PCR. Experimental hypothyroid rats were produced by total thyroidectomy and were then killed 7 days after the operation. TRH receptor binding in the anterior pituitary and serum TSH level were elevated approximately 2-fold and 8-fold, respectively, in 7 day thyroidectomized rats. TRH-R mRNA levels in hypothyroid rats were also increased significantly compared with those of normal rats. In GH3 cells, however, no significant change of TRH-R mRNA level was observed between cultures treated with triiodothyronine (T3, 10(-9) and 10(-7) M) and the untreated group. The present data indicate that 1) the in vivo effects of thyroid status on TRH-R mRNA levels differ from the in vitro one, and that 2) the down regulation of TRH-R binding by thyroid hormone in GH3 cells may be mediated by translational or post-translational mechanisms.
我们运用克隆的大鼠促甲状腺激素释放激素受体（TRH-R）cDNA，通过逆转录聚合酶链反应（RT-PCR），在体内和体外（GH3细胞）研究了甲状腺状态对TRH-R mRNA水平的影响。通过全甲状腺切除术制备实验性甲状腺功能减退大鼠，术后7天处死。在术后7天的甲状腺切除大鼠中，垂体前叶TRH受体结合力和血清促甲状腺激素（TSH）水平分别升高约2倍和8倍。与正常大鼠相比，甲状腺功能减退大鼠的TRH-R mRNA水平也显著升高。然而，在GH3细胞中，用三碘甲状腺原氨酸（T3，10^(-9)和10^(-7) M）处理的培养物与未处理组之间，未观察到TRH-R mRNA水平有显著变化。目前的数据表明：1）甲状腺状态对TRH-R mRNA水平的体内影响与体外影响不同；2）甲状腺激素对GH3细胞中TRH-R结合的下调可能是由翻译或翻译后机制介导的。
