Sanchez-Prieto J, Sihra T S, Nicholls D G
J Neurochem. 1987 Jul;49(1):58-64. doi: 10.1111/j.1471-4159.1987.tb03394.x.
A continuous enzyme-linked fluorometric assay was used for determining the characteristics for glutamate exocytosis from guinea-pig cerebrocortical synaptosomes. Ca2+-dependent release can be induced not only by K+, but also by the Na+ channel activator veratridine and the Ca2+ ionophore ionomycin. K+-induced release can be inhibited by the Ca2+ channel inhibitor verapamil. Sr2+ and Ba2+ substitute for Ca2+ in promoting K+-induced release. Agents that would be predicted to transform the transvesicular pH gradient into a membrane potential are without effect on glutamate release. However, the protonophore carbonylcyanide p-trifluoromethoxyphenylhydrazone causes a time-dependent loss of exocytosis that is oligomycin insensitive and may be due to depletion of vesicular glutamate. The Ca2+-independent release of glutamate from the cytosol on depolarization is unchanged or promoted by metabolic inhibitors that lower the ATP/ADP ratio. In contrast. Ca2+-dependent release is ATP dependent and is blocked by the combined inhibition of oxidative phosphorylation and glycolysis.
采用连续酶联荧光分析法测定豚鼠大脑皮质突触体谷氨酸胞吐作用的特征。Ca2+ 依赖性释放不仅可由 K+ 诱导，还可由 Na+ 通道激活剂藜芦碱和 Ca2+ 离子载体离子霉素诱导。K+ 诱导的释放可被 Ca2+ 通道抑制剂维拉帕米抑制。Sr2+ 和 Ba2+ 在促进 K+ 诱导的释放方面可替代 Ca2+。预计会将跨囊泡pH梯度转化为膜电位的试剂对谷氨酸释放没有影响。然而，质子载体羰基氰化物对三氟甲氧基苯腙会导致胞吐作用随时间丧失，这种丧失对寡霉素不敏感，可能是由于囊泡谷氨酸耗竭所致。去极化时谷氨酸从胞质溶胶中的 Ca2+ 非依赖性释放不受降低ATP/ADP比值的代谢抑制剂影响或被促进。相反，Ca2+ 依赖性释放依赖于ATP，并被氧化磷酸化和糖酵解的联合抑制所阻断。
