Tahara K, Grollman E F, Saji M, Kohn L D
Section of Cell Regulation, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
J Biol Chem. 1991 Jan 5;266(1):440-8.
The present report shows that thyrotropin (TSH) regulates all three steps involved in prostaglandin synthesis in FRTL-5 rat thyroid cells, i.e. arachidonic acid release from membrane phospholipids, cyclooxygenase (prostaglandin H synthase) action, and individual prostaglandin formation; however, its action at specific steps may require the presence of, or can be duplicated by, insulin, insulin-like growth factor-I (IGF-I), and/or a serum factor. Thus, TSH releases free arachidonic acid from rat FRTL-5 thyroid cells whose phospholipid fraction is radiolabeled with [3H]arachidonic acid; this action involves a pertussis toxin-sensitive G protein, is not cAMP mediated, and does not require insulin or 5% serum. To quantitate TSH effects on cyclooxygenase activity and on individual prostaglandin formation, a homogenate system and a rapid reversed-phase high pressure liquid chromatography procedure have been developed to measure cyclooxygenase metabolites. TSH increased cyclooxygenase activity in homogenates only if the cells were also exposed to insulin, IGF-I, and/or 5% calf serum; TSH alone had no apparent effect on the activity. Maximal activation, 4-fold over basal/micrograms of DNA, took 36 h to achieve and reflected, at least in part, an increase in cyclooxygenase gene expression. Like cyclooxygenase activity, induction of prostaglandin E2 production required 2 or more factors, i.e. TSH plus insulin/IGF-I or TSH plus insulin/IGF-I plus serum. Increased production of prostaglandin D2, could, however, be detected if cells were treated with TSH alone and the TSH activity could be duplicated by insulin, IGF-I, or calf serum alone.
本报告显示，促甲状腺激素（TSH）调节FRTL-5大鼠甲状腺细胞中前列腺素合成所涉及的所有三个步骤，即从膜磷脂释放花生四烯酸、环氧合酶（前列腺素H合成酶）的作用以及单个前列腺素的形成；然而，其在特定步骤的作用可能需要胰岛素、胰岛素样生长因子-I（IGF-I）和/或血清因子的存在，或者可以被它们所替代。因此，TSH从磷脂部分用[3H]花生四烯酸进行放射性标记的大鼠FRTL-5甲状腺细胞中释放游离花生四烯酸；该作用涉及一种对百日咳毒素敏感的G蛋白，不是由cAMP介导的，并且不需要胰岛素或5%血清。为了定量TSH对环氧合酶活性和单个前列腺素形成的影响，已经开发了一种匀浆系统和一种快速反相高压液相色谱程序来测量环氧合酶代谢产物。只有当细胞也暴露于胰岛素、IGF-I和/或5%小牛血清时，TSH才会增加匀浆中的环氧合酶活性；单独的TSH对该活性没有明显影响。最大激活程度为基础水平的4倍/微克DNA，需要36小时才能达到，并且至少部分反映了环氧合酶基因表达的增加。与环氧合酶活性一样，前列腺素E2产生的诱导需要两种或更多种因子，即TSH加胰岛素/IGF-I或TSH加胰岛素/IGF-I加血清。然而，如果单独用TSH处理细胞，并且单独的胰岛素、IGF-I或小牛血清可以模拟TSH的活性，就可以检测到前列腺素D2产生的增加。
