Méndez M, Cisneros M, Baez A, Joseph-Bravo P, Charli J L
Departamento de Genética y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, MEXICO.
Neurochem Res. 1999 Jul;24(7):815-23. doi: 10.1023/a:1020993527602.
TRH-like immunoreactivity distinct from TRH is present in various tissues and fluids. In order to determine whether TRH-like molecules are secreted by the hypothalamus, we analyzed tissues and media from hypothalamic slices incubated in Krebs Ringer bicarbonate. Media from basal or high KCl conditions contained 3 TRH-like molecules evidenced by reverse phase high performance liquid chromatography followed by TRH radioimmunoassay. Peak I corresponded to authentic TRH (73% of total immunoreactivity) and peaks II and III had a higher retention time. These additional TRH-like forms were neither detected in hypothalamic tissue nor in tissue or medium from olfactory bulb. Gel filtration analysis of hypothalamic media revealed only one TRH-like peak eluting as TRH, suggesting that the molecular weights of peaks II and III are similar to that of TRH. Peak II retention time was similar to that of pglu-phe-proNH2. We analysed if they could be produced by post secretory metabolism of TRH. Incubation of hypothalamic slices with [3H-Pro]-TRH did not produce radioactive species comigrating with peaks II or III. However, it induced rapid degradation to [3H-Pro]-his-prodiketopiperazine ([3H]-HPDKP). Inhibitor profile suggested that pyroglutamyl aminopeptidase II, but not pyroglutamyl aminopeptidase I, is responsible for [3H]-HPDKP production. These data are consistent with the hypothesis that pyroglutamyl aminopeptidase II is the main aminopeptidase degrading TRH in hypothalamic extracellular fluid. Furthermore, we suggest that the hypothalamus releases additional TRH-like molecules, one of them possibly pglu-phe-proNH2, which may participate in control of adenohypophyseal secretions.
在各种组织和体液中存在与促甲状腺激素释放激素（TRH）不同的TRH样免疫反应性物质。为了确定TRH样分子是否由下丘脑分泌，我们分析了在碳酸氢盐林格氏液中孵育的下丘脑切片的组织和培养基。基础或高钾条件下的培养基中含有3种TRH样分子，这通过反相高效液相色谱法随后进行TRH放射免疫测定得以证实。峰I对应于 authentic TRH（占总免疫反应性的73%），峰II和峰III具有更长的保留时间。这些额外的TRH样形式在下丘脑组织以及嗅球的组织或培养基中均未检测到。下丘脑培养基的凝胶过滤分析仅显示出一个以TRH形式洗脱的TRH样峰，这表明峰II和峰III的分子量与TRH相似。峰II的保留时间与焦谷氨酸 - 苯丙氨酸 - 脯氨酰胺（pglu - phe - proNH2）相似。我们分析了它们是否可能由TRH的分泌后代谢产生。用[3H - 脯氨酸] - TRH孵育下丘脑切片并未产生与峰II或峰III共迁移的放射性物质。然而，它诱导了快速降解为[3H - 脯氨酸] - 组氨酸 - 二酮哌嗪（[3H] - HPDKP）。抑制剂谱表明，焦谷氨酰氨基肽酶II而非焦谷氨酰氨基肽酶I负责[3H] - HPDKP的产生。这些数据与以下假设一致，即焦谷氨酰氨基肽酶II是下丘脑细胞外液中降解TRH的主要氨基肽酶。此外，我们认为下丘脑释放额外的TRH样分子，其中之一可能是pglu - phe - proNH2，它可能参与腺垂体分泌的调控。
