Santos M S, Gonçalves P P, Carvalho A P
Neurochem Res. 1987 Mar;12(3):297-304. doi: 10.1007/BF00972140.
Exogenous tritiated gamma-aminobutiric acid ([3H]GABA) is retained in two compartments in sheep cortex synaptosomes, corresponding to cytoplasmic and vesicular spaces, assuming that freeze-thawing the synaptosomes loaded with [3H]GABA releases the cytoplasmic [3H]GABA (81 +/- 3.9%), and that subsequent solubilization of the synaptosomes with 1% sodium cholate releases the vesicular [3H]GABA (19 +/- 3.9%). Depolarization of synaptosomes with 40 mM K+ in a Na+-medium, in the absence of Ca2+, releases 20.3 +/- 2.7% of the [3H]GABA retained in the synaptosomes. The [3H]GABA released under these conditions comes predominantly from the cytoplasm. The presence of 1 mM Ca2+ during depolarization releases an additional 13% (a total of about 33.5 +/- 9.9%) of the releasable [3H]GABA, and the [3H]GABA release which is Ca2+-dependent also comes mostly from the cytoplasmic compartment. When choline replaces external Na+, the [3H]GABA release is absolutely Ca2+-dependent, and the [3H]GABA released also comes mostly from the cytoplasmic pool. Therefore, it appears that [3H]GABA taken up by synaptosomes is accumulated mostly in the cytoplasmic compartment from which it is released upon depolarization. The technique described permits distinguishing the effect of different factors on the two pools of accumulated [3H]GABA.
外源性氚标记的γ-氨基丁酸（[3H]GABA）保留在绵羊皮层突触体的两个区室中，分别对应细胞质和囊泡空间，这是基于以下假设：对装载有[3H]GABA的突触体进行冻融处理会释放出细胞质中的[3H]GABA（81±3.9%），随后用1%的胆酸钠溶解突触体则会释放出囊泡中的[3H]GABA（19±3.9%）。在无Ca2+的Na+介质中，用40 mM K+使突触体去极化，会释放出突触体中保留的[3H]GABA的20.3±2.7%。在这些条件下释放的[3H]GABA主要来自细胞质。去极化过程中存在1 mM Ca2+时，会额外释放出可释放的[3H]GABA的13%（总共约33.5±9.9%），且依赖Ca2+的[3H]GABA释放也大多来自细胞质区室。当胆碱取代细胞外的Na+时，[3H]GABA的释放绝对依赖Ca2+，且释放的[3H]GABA也大多来自细胞质池。因此，似乎突触体摄取的[3H]GABA大多积累在细胞质区室中，去极化时从该区室释放出来。所描述的技术能够区分不同因素对积累的[3H]GABA的两个池的影响。
