Glutamate transport, glutamine synthetase and phosphate-activated glutaminase in rat CNS white matter. A quantitative study
Glutamate transport, glutamine synthetase and phosphate-activated glutaminase in rat CNS white matter. A quantitative study
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DOI：
10.1046/j.1471-4159.2003.01984.x
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发表时间：
2003-10-01
影响因子：
4.7
通讯作者：
Skrede, KK
中科院分区：
文献类型：
--
作者：
Hassel, B;Boldingh, KA;Skrede, KK
谷氨酸能信号转导发生在中枢神经系统白色物质中，但缺乏谷氨酸摄取和代谢的定量数据。我们报道了大鼠海马伞和胼胝体中星形胶质细胞谷氨酸转运体GLT的水平与顶叶皮层中的水平相似，[H-3]谷氨酸的摄取分别为皮层值的24%和43%。在海马伞和胼胝体水平的突触蛋白，synapsin I和突触素是皮质的15 - 20%;谷氨酰胺合成酶和磷酸活化的谷氨酸氨基转移酶，参与递质谷氨酸代谢的酶，活性是皮质值的11-25%，天冬氨酸和丙氨酸氨基转移酶的活性是皮质值的50-70%。海马伞和胼胝体中的谷氨酸水平为5 - 6 nmol/mg组织，是皮质值的一半。这些数据表明，有一定的能力，为amatergic神经传递。在视神经和三叉神经中，[H-3]谷氨酸摄取<皮质摄取的10%。清醒大鼠海马伞和胼胝体中[U-C-14]葡萄糖形成的[C-14]谷氨酸是皮质值的30%，在视神经中是13%，说明体内白色物质中广泛的谷氨酸代谢。脑白色物质中的谷氨酸转运蛋白可能在生理学上和能量衰竭期间都很重要，此时谷氨酸摄取的逆转可能导致兴奋性毒性。
Glutamatergic signal transduction occurs in CNS white matter, but quantitative data on glutamate uptake and metabolism are lacking. We report that the level of the astrocytic glutamate transporter GLT in rat fimbria and corpus callosum was similar to35% of that in parietal cortex; uptake of [H-3] glutamate was 24 and 43%, respectively, of the cortical value. In fimbria and corpus callosum levels of synaptic proteins, synapsin I and synaptophysin were 15 - 20% of those in cortex; the activities of glutamine synthetase and phosphate-activated glutaminase, enzymes involved in metabolism of transmitter glutamate, were 11-25% of cortical values, and activities of aspartate and alanine aminotransferases were 50-70% of cortical values. The glutamate level in fimbria and corpus callosum was 5 - 6 nmol/mg tissue, half the cortical value. These data suggest a certain capacity for glutamatergic neurotransmission. In optic and trigeminal nerves, [H-3] glutamate uptake was < 10% of the cortical uptake. Formation of [C-14] glutamate from [U-C-14] glucose in fimbria and corpus callosum of awake rats was 30% of cortical values, in optic nerve it was 13%, illustrating extensive glutamate metabolism in white matter in vivo. Glutamate transporters in brain white matter may be important both physiologically and during energy failure when reversal of glutamate uptake may contribute to excitotoxicity.