Faccenda E, Melmed S, Bevan J S, Eidne K A
MRC Reproductive Biology Unit, Centre for Reproductive Biology, Edinburgh, UK.
Clin Endocrinol (Oxf). 1996 Mar;44(3):341-7. doi: 10.1046/j.1365-2265.1996.684506.x.
TRH acts on specific G-protein coupled receptors sited in cells of the anterior pituitary gland. Pituitary tumours expressing either TSH, PRL or GH may respond to TRH by enhanced, blunted or paradoxical hormone release. Non-functioning pituitary tumours may also show abnormal responses to TRH. Little is understood of the mechanisms regulating inappropriate hormone release in these tumours. Activating or inactivating mutations found in G-protein coupled receptors have been implicated in human pathological conditions. Mutations in the G-protein coupled TRH receptor might be involved in the aetiology of pituitary adenomas resulting in aberrant hormone secretion. We therefore screened samples of pituitary adenomas for the presence of somatic mutations in the TRH receptor gene.
Pituitary adenoma tissue samples were obtained at surgery from 50 patients with pituitary adenoma (17 acromegaly, 15 prolactinoma, 11 TSH-secreting and 7 non-functioning adenoma) along with blood samples to provide lymphocyte DNA as control sequence.
Genomic DNA was extracted from adenoma and lymphocyte samples and the entire coding region of the TRH receptor was amplified using 5 overlapping pairs of PCR primers. The PCR products were analysed for mutations by non-denaturing polyacrylamide gel electrophoresis which reveals single-strand conformational polymorphisms (SSCP) as a mobility shift in product migration. Wild-type and mutant TRH receptor cDNA were similarly analysed to confirm the sensitivity of the method. Additionally, PCR products were ligated into a PCR cloning vector and DNA sequencing carried out to confirm the findings of SSCP analysis.
The human TRH receptor retained normal wild-type sequence in the large group of TSH secreting, PRL secreting, GH secreting and non-functioning pituitary adenomas investigated in this study.
Our observations suggest that the TRH receptor structure is normal in TSH secreting, PRL secreting, GH secreting and non-functioning pituitary adenomas. It is therefore unlikely that the TRH receptor is involved in the pathology associated with the types of pituitary adenomas investigated in this study. It is possible that some other component of the pathway controlling TRH-signalling events may be implicated in pituitary tumorigenesis.
促甲状腺激素释放激素（TRH）作用于位于垂体前叶细胞中的特定G蛋白偶联受体。表达促甲状腺激素（TSH）、催乳素（PRL）或生长激素（GH）的垂体瘤可能对TRH产生激素释放增强、减弱或矛盾的反应。无功能垂体瘤对TRH也可能表现出异常反应。目前对这些肿瘤中调节激素异常释放的机制了解甚少。G蛋白偶联受体中发现的激活或失活突变与人类病理状况有关。G蛋白偶联的TRH受体突变可能参与垂体腺瘤的病因学，导致激素分泌异常。因此，我们筛查了垂体腺瘤样本中TRH受体基因的体细胞突变情况。
从50例垂体腺瘤患者手术中获取垂体腺瘤组织样本（17例肢端肥大症、15例催乳素瘤、11例分泌TSH的腺瘤和7例无功能腺瘤），同时采集血样以提供淋巴细胞DNA作为对照序列。
从腺瘤和淋巴细胞样本中提取基因组DNA，使用5对重叠的PCR引物扩增TRH受体的整个编码区。通过非变性聚丙烯酰胺凝胶电泳分析PCR产物的突变情况，该方法可通过产物迁移的迁移率变化揭示单链构象多态性（SSCP）。对野生型和突变型TRH受体cDNA进行类似分析以确认该方法的敏感性。此外，将PCR产物连接到PCR克隆载体中并进行DNA测序以确认SSCP分析的结果。
在本研究中调查的大量分泌TSH、分泌PRL、分泌GH和无功能垂体腺瘤中，人类TRH受体保留了正常的野生型序列。
我们的观察结果表明，在分泌TSH、分泌PRL、分泌GH和无功能垂体腺瘤中，TRH受体结构正常。因此，TRH受体不太可能参与本研究中所调查类型的垂体腺瘤相关的病理过程。控制TRH信号事件的途径中的某些其他成分可能与垂体肿瘤发生有关。
