Svarna R, Georgopoulos A, Palaiologos G
Laboratory of Biological Chemistry, Medical School, University of Athens, Greece.
Neurochem Res. 1996 May;21(5):603-8. doi: 10.1007/BF02527759.
The effect of aminooxyacetic acid (AOAA), NH4+, phenylsuccinate (Phs), ketone bodies (KB) and glutamine (Gln), that might interfere with the biosynthesis of neurotransmitter glutamate on the K(+)-evoked Ca(2+)-dependent release of D-[3H]aspartate from rat cerebellar slices was studied. Therefore slices were preincubated in a Krebs-Ringer-bicarbonate-glucose (KR) buffer, loaded with D-[3H]aspartate and superfused in the presence of Ca2+ or when Ca2+ was replaced by Mg2+ or in some cases by EGTA. AOAA, NH4+ and Phs increase the K(+)-evoked Ca(2+)-dependent release of radioactivity by 30%, 68% and 188% compared to the control respectively indicating that these agents are inhibitors of the K(+)-evoked Ca(2+)-dependent release of glutamate. KB and Gln had no effect on the Ca(2+)-dependent release of radioactivity. AOAA, NH4+, Phs and KB but not Gln increase the total release of radioactivity by 43%, 69%, 139%, and 37% respectively. AOAA, NH4+ and KB but not Phs or Gln increase the Ca(2+)-independent release (Mg2+ replacing Ca2+) of radioactivity by 71%, 71% and 108% respectively. The present results indicate that in the cerebellum: 1) Neurotransmitter glutamate is mostly synthesized through the phosphate activated glutaminase (PAG) reaction 2) It is further supported that glutamate released in Ca(2+)-dependent manner before entering its pool in the cytosol has to move into the mitochondrial matrix.
研究了氨基氧乙酸（AOAA）、NH₄⁺、苯琥珀酸（Phs）、酮体（KB）和谷氨酰胺（Gln）对大鼠小脑切片中K⁺诱发的Ca²⁺依赖性D-[³H]天冬氨酸释放的影响，这些物质可能会干扰神经递质谷氨酸的生物合成。因此，将切片在 Krebs-Ringer-碳酸氢盐-葡萄糖（KR）缓冲液中预孵育，加载D-[³H]天冬氨酸，并在存在Ca²⁺的情况下或当Ca²⁺被Mg²⁺替代时，或在某些情况下被乙二醇双四乙酸（EGTA）替代时进行灌流。与对照组相比，AOAA、NH₄⁺和Phs分别使K⁺诱发的Ca²⁺依赖性放射性释放增加30%、68%和188%，表明这些物质是K⁺诱发的Ca²⁺依赖性谷氨酸释放的抑制剂。KB和Gln对Ca²⁺依赖性放射性释放没有影响。AOAA、NH₄⁺、Phs和KB但不是Gln分别使放射性的总释放增加43%、69%、139%和37%。AOAA、NH₄⁺和KB但不是Phs或Gln分别使放射性的Ca²⁺非依赖性释放（Mg²⁺替代Ca²⁺）增加71%、71%和108%。目前的结果表明，在小脑中：1）神经递质谷氨酸大多通过磷酸激活谷氨酰胺酶（PAG）反应合成；2）进一步支持了以Ca²⁺依赖性方式释放的谷氨酸在进入其胞质溶胶池之前必须进入线粒体基质。
