Johnstone R M
Biochim Biophys Acta. 1978 Sep 11;512(1):199-213. doi: 10.1016/0005-2736(78)90230-4.
Influx and efflux of glycine have been examined as a function of external and internal Na+ concentrations, respectively, when : formula: (see text) = O. With : formula: (see text) = O it was found that at comparable external and cellular Na+ levels, the Km for efflux was larger by an order of magnitude than the value for influx and the V for efflux was several times greater than the V for influx. For both fluxes the major effect of Na+ was to decrease the Km value. The observations are consistent with the conclusion that the Na+-dependent transport system is asymmetric per se. Influx and efflux of glycine were increased in a near linear manner by increasing the Na+ concentration from 13 to 100 mM, the half-time for glycine equilibration being a funcion of the Na+ concentration in absence of an electrochemical potential difference for Na+. In Na+-free media ([Na+] less than 5 mM) equilibration of glycine between cells and medium was not achieved after 60 min at 25 degrees C. With : formula: (see text) = O, efflux (or uptake) of glycine was not affected by internal (or external) K+ between 20 and 120 mM suggesting that K+ plays no direct role in Na+-dependent transport of glycine in Ehrlich cells.
公式：（见原文）= 0时，分别研究了甘氨酸的流入和流出与外部和内部Na⁺浓度的关系。当：公式：（见原文）= 0时，发现在外部和细胞内Na⁺水平相当的情况下，流出的Km比流入的值大一个数量级，且流出的V比流入的V大几倍。对于这两种通量，Na⁺的主要作用是降低Km值。这些观察结果与以下结论一致，即Na⁺依赖性转运系统本身是不对称的。通过将Na⁺浓度从13 mM增加到100 mM，甘氨酸的流入和流出以近线性方式增加，在没有Na⁺电化学势差的情况下，甘氨酸平衡的半衰期是Na⁺浓度的函数。在无Na⁺培养基（[Na⁺]小于5 mM）中，在25℃下60分钟后，细胞与培养基之间的甘氨酸未达到平衡。当：公式：（见原文）= 0时，在20至120 mM之间，甘氨酸的流出（或摄取）不受内部（或外部）K⁺的影响，这表明K⁺在艾氏腹水癌细胞中Na⁺依赖性甘氨酸转运中不发挥直接作用。
