15N-NMR spectroscopy studies of ammonia transport and glutamine synthesis in the hyperammonemic rat brain.
15N-NMR spectroscopy studies of ammonia transport and glutamine synthesis in the hyperammonemic rat brain.
复制标题
高氨大鼠脑中氨转运和谷氨酰胺合成的 15N-NMR 波谱研究。
DOI：
10.1159/000017341
复制
发表时间：
1998
影响因子：
2.9
通讯作者：
Shulman,RG
中科院分区：
文献类型：
--
作者：
Shen,J;Sibson,NR;Cline,G;Behar,KL;Rothman,DL;Shulman,RG
通过静脉注射[15N]-醋酸铵，在血浆氨水平约为0.39 mM时，用15N-NMR光谱法研究了高氨血症大鼠脑中氨转运和谷氨酰胺合成。使用脑15 N标记代谢物总和的时间进程的初始斜率确定高氨血症期间氨净转运速率为0.13 ± 0.02 µ mol/min/g（平均值± SD; n = 5）。根据谷氨酰胺的总积累和四碳骨架与氮原子通量之间的1：2化学计量关系，计算出通过回补和随后的谷氨酸脱氢酶作用从头合成谷氨酰胺的速率为0.065 ± 0.01 µ mol/min/g。通过将[5 - 15 N]谷氨酰胺时程拟合到先前描述的星形胶质细胞和神经元之间的谷氨酸-谷氨酰胺循环模型，估计总谷氨酰胺合成速率为0.20 ± 0.06 µ mol/min/g（n = 5）。在[2 - 15 N]谷氨酰胺中也观察到大量稀释，这支持谷氨酸-谷氨酰胺循环是体内神经元谷氨酸补充的重要途径。
Ammonia transport and glutamine synthesis were studied in the hyperammonaemic rat brain in vivo using15N-NMR spectroscopy at a plasma ammonia level of approximately 0.39 mMraised via an intravenous [15N]-ammonium acetate infusion. The initial slope of the time course of the summed cerebral15N-labelled metabolites was used to determine the rate of ammonia net transport during hyperammonemia as 0.13 ± 0.02 µmol/min/g (mean ± SD; n = 5). Based on the total accumulation of glutamine and the 1:2 stoichiometric relationship between fluxes of four-carbon skeletons and nitrogen atoms, the rate of de novo glutamine synthesis through anaplerosis and subsequent glutamate dehydrogenase action was calculated to be 0.065 ± 0.01 µmol/min/g. The rate of total glutamine synthesis was estimated to be 0.20 ± 0.06 µmol/min/g (n = 5) by fitting the [5-15N]glutamine time course to a previously described model of glutamate-glutamine cycling between astrocytes and neurones. A large dilution was also observed in [2-15N]glutamine, which supports the glutamate-glutamine cycle as being an important pathway for neuronal glutamate repletion in vivo.