Diurnal change of thyroid-stimulating hormone mRNA expression in the rat pars tuberalis
Diurnal change of thyroid-stimulating hormone mRNA expression in the rat pars tuberalis
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DOI：
10.1111/j.1365-2826.2007.01603.x
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发表时间：
2007-11-01
影响因子：
3.2
通讯作者：
Sakai, T.
中科院分区：
文献类型：
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作者：
Aizawa, S.;Hoshino, S.;Sakai, T.
促甲状腺激素（TSH）产生细胞（TSH细胞）占大鼠结节部（PT）细胞的很大一部分，已被发现高密度表达MT1褪黑激素受体和哺乳动物时钟基因。虽然这些研究结果表明,鼠TSH生产PT是受褪黑素和/或生物时钟,没有研究关注的昼夜变化和监管机制在老鼠PT TSH生产。因此,在目前的研究中,我们检查了昼夜变化的TSH beta和alpha-glycoprotein亚基(αGSU) mRNA表达和TSH免疫反应性(ir)鼠PT,并检查体内褪黑素和TSH生产之间的关系。PT中TSH β mRNA和α - GSU mRNA表达均呈日变化，在光照期[Zeitgeber time (ZT)4]表达水平最低，在暗期（ZT12和ZT20）表达水平较高。PT中TSH-ir在ZT4表达水平最低，mRNA表达水平亦是如此。有趣的是，在ZT4时局限于高尔基体的TSH-ir扩散到细胞质中，并且在ZT20时，PT中的大多数TSH细胞在细胞质中均匀免疫染色。尽管长期服用褪黑激素抑制了TSH β和α GSU mRNA的表达，但PT中的TSH-ir显著增强。这些结果清楚地表明，大鼠PT-TSH细胞中TSH的表达和积累存在昼夜变化，这些波动受褪黑激素的调节。
Thyroid-stimulating hormone (TSH)-producing cells (TSH cells), which account for a large fraction of the cells in the rat pars tuberalis (PT), have been found to express MT1 melatonin receptor and mammalian clock genes at high densities. Although these findings suggest that TSH production in the rat PT is regulated by melatonin and/or the biological clock, there have been no studies focusing on the diurnal change and regulation mechanism of TSH production in the rat PT. Therefore, in the present study, we examined diurnal changes of in TSH beta and alpha-glycoprotein subunit (alpha GSU) mRNA expression and TSH immunoreactivity (-ir) in the rat PT, and also examined the relationship between melatonin and TSH production in vivo. Both TSH beta mRNA expression and alpha GSU mRNA expression in the PT showed diurnal variations: the expression levels were lowest at the light phase [Zeitgeber time (ZT)4] and high at the dark phase (ZT12 and ZT20). TSH-ir in the PT showed the lowest level at ZT4, as was found for mRNA expression. Interestingly, TSH-ir, which was confined to the Golgi apparatus at ZT4, spread to the cytoplasm, and most of the TSH cells in the PT were uniformly immunostained in the cytoplasm at ZT20. Despite the fact that chronic administration of melatonin suppressed TSH beta and alpha GSU mRNA expression, TSH-ir in the PT was significantly enhanced. These findings results clearly show that there are diurnal changes in TSH expression and accumulation in rat PT-TSH cells and suggest that these fluctuations are regulated by melatonin.