Laris P C, Bootman M, Pershadsingh H A, Johnstone R M
Biochim Biophys Acta. 1978 Sep 22;512(2):397-414. doi: 10.1016/0005-2736(78)90263-8.
The membrane potential of the Ehrlich ascites tumor cell was shown to be influenced by its amino acid content and the activity of the Na+ :K+ pump. The membrane potential (monitored by the fluorescent dye, 3,3'-dipropylthiodicarbocyanine iodide) varied with the size of the endogenous amino acid pool and with the concentration of accumulated 2-aminoisobutyrate. When cellular amino acid content was high, the cells were hyperpolarized; as the pool declined in size, the cells were depolarized. The hyperpolarization seen with cellular amino acid required cellular Na+ but not cellular ATP. Na+ efflux was more rapid from cells containing 2-aminoisobutyrate than from cells low in internal amino acids. These observations indicate that the hyperpolarization recorded in cells with high cellular amino acid content resulted from the electrogenic co-efflux of Na+ and amino acids. Cellular ATP levels were found to decline rapidly in the presence of the dye and hence the influence of the pump was seen only if glucose was added to the cells. When the cells contained normal Na+ (approx. 30mM), the Na+ :K+ pump was shown to have little effect on the membrane potential (the addition of ouabain had little effect on the potential). When cellular Na+ was raised to 60mM, the activity of the pump changed the membrane potential from the range -25 to -30 mV to -44 to -63 mV. This hyperpolarization required external K+ and was inhibited by ouabain.
艾氏腹水癌细胞的膜电位被证明受其氨基酸含量和Na⁺:K⁺泵活性的影响。膜电位（通过荧光染料3,3'-二丙基硫代二羰花青碘化物监测）随内源性氨基酸池的大小以及积累的2-氨基异丁酸浓度而变化。当细胞内氨基酸含量高时，细胞发生超极化；随着氨基酸池大小减小，细胞发生去极化。细胞氨基酸引起的超极化需要细胞内的Na⁺但不需要细胞内的ATP。含有2-氨基异丁酸的细胞比内部氨基酸含量低的细胞的Na⁺外流更快。这些观察结果表明，细胞内氨基酸含量高的细胞中记录到的超极化是由Na⁺和氨基酸的电生性协同外流导致的。发现在有染料存在的情况下细胞内ATP水平迅速下降，因此只有向细胞中添加葡萄糖时才能看到泵的影响。当细胞含有正常的Na⁺（约30mM）时，Na⁺:K⁺泵对膜电位几乎没有影响（添加哇巴因对电位几乎没有影响）。当细胞内Na⁺升高到60mM时，泵的活性将膜电位从-25至-30mV的范围改变为-44至-63mV。这种超极化需要细胞外的K⁺，并被哇巴因抑制。
