Smith L F, Pycock C J
J Neurochem. 1982 Sep;39(3):653-8. doi: 10.1111/j.1471-4159.1982.tb07942.x.
The release of preloaded [3H]glycine and [3H]taurine in response to a depolarising stimulus (12.5-50 mM KCl) has been studied in the superfused rat retina. High external potassium concentration immediately increased the spontaneous efflux of [3H]glycine, the effect of 50 mM K+ apparently being abolished by omitting calcium from the superfusing medium. In contrast, although high potassium concentrations increased the spontaneous efflux of [3H]taurine from the superfused rat retina, this release was not evident until the depolarising stimulus was removed from the superfusing medium. The magnitude of this "late" release of [3H]taurine was dependent on external K+ concentrations, and appeared immediately after cessation of the stimulus irrespective of whether it was applied for 4, 8, or 12 min. Potassium (50 mM)-induced release of taurine appeared partially calcium-dependent, being significantly reduced (p less than 0.01) but not abolished by replacing calcium with 1 mM EDTA in the superfusate. High-affinity uptake systems for both [3H]glycine and [3H]taurine were demonstrated in the rat retina in vitro (Km values, 1.67 microM and 2.97 microM; Vmax values, 19.3 and 23.1 nmol/g wet weight tissue/h, respectively). The results are discussed with respect to the possible neurotransmitter roles of both amino acids in the rat retina.
在体外灌流的大鼠视网膜中，研究了预加载的[3H]甘氨酸和[3H]牛磺酸对去极化刺激（12.5 - 50 mM KCl）的释放情况。高细胞外钾浓度立即增加了[3H]甘氨酸的自发外流，当灌流液中去除钙时，50 mM K+的这种作用明显被消除。相反，虽然高钾浓度增加了灌流大鼠视网膜中[3H]牛磺酸的自发外流，但这种释放直到灌流液中去除去极化刺激后才明显。[3H]牛磺酸这种“延迟”释放的幅度取决于细胞外K+浓度，并且在刺激停止后立即出现，无论刺激施加4、8或12分钟。钾（50 mM）诱导的牛磺酸释放似乎部分依赖于钙，当灌流液中用1 mM EDTA替代钙时，释放显著减少（p < 0.01）但未被消除。在体外大鼠视网膜中证实了[3H]甘氨酸和[3H]牛磺酸的高亲和力摄取系统（Km值分别为1.67 microM和2.97 microM；Vmax值分别为19.3和23.1 nmol/g湿重组织/小时）。针对这两种氨基酸在大鼠视网膜中可能的神经递质作用对结果进行了讨论。
