Bussolati O, Laris P C, Nucci F A, Dall'Asta V, Franchi-Gazzola R, Guidotti G G, Gazzola G C
Istituto di Patologia Generale, Universitá, di Parma, Italy.
Am J Physiol. 1989 Apr;256(4 Pt 1):C930-5. doi: 10.1152/ajpcell.1989.256.4.C930.
The net influx of L-arginine (JARG) was employed as an indicator of the membrane potential in human fibroblasts. Cell depolarization, obtained by increasing [K+]out, decreased both JARG and the net influx of the lipid soluble cation tetraphenylphosphonium (JTPP), a probe of membrane potential. JTPP, but not JARG, was influenced by the mitochondrial potential and exhibited a component dependent on intracellular and/or extracellular binding. JARG was sensitive to changes in the membrane potential induced by Na+-dependent transport of L-proline or by the activity of Na+-K+-ATPase. In the presence of 50 microM valinomycin, JARG was markedly influenced by the distribution ratio of K+ in a range of [K+]out from 1.5 to 100 mM. In this range of [K+]out, membrane potential (Em) varied from -90 to -23 mV, and calibration of JARG vs. the membrane potential yielded a linear relationship. These results indicate the following: 1) that the net influx of TPP+ is not a reliable indicator of membrane potential in cultured human fibroblasts; 2) that in the same cells the net influx of L-arginine can be employed as an index of membrane potential; 3) that in a range of Em from -23 to -90 mV the activity of system y+ (the membrane agency devoted to L-arginine transport in cultured human fibroblasts) exhibits no saturation of potential-dependent activation of transport.
L-精氨酸的净内流（JARG）被用作人类成纤维细胞膜电位的指标。通过增加细胞外[K⁺]获得的细胞去极化，降低了JARG以及脂溶性阳离子四苯基鏻（JTPP）的净内流，JTPP是膜电位的一种探针。JTPP受线粒体电位影响，但JARG不受影响，并且JTPP表现出一种依赖于细胞内和/或细胞外结合的成分。JARG对由L-脯氨酸的Na⁺依赖性转运或Na⁺-K⁺-ATP酶的活性所诱导的膜电位变化敏感。在存在50 μM缬氨霉素的情况下，在细胞外[K⁺]从1.5到100 mM的范围内，JARG受到K⁺分布比的显著影响。在此细胞外[K⁺]范围内，膜电位（Em）从 -90 mV变化到 -23 mV，并且JARG与膜电位的校准产生了线性关系。这些结果表明：1）TPP⁺的净内流不是培养的人类成纤维细胞膜电位的可靠指标；2）在相同细胞中，L-精氨酸的净内流可被用作膜电位的指标；3）在Em从 -23 mV到 -90 mV的范围内，系统y⁺（负责培养的人类成纤维细胞中L-精氨酸转运的膜机制）的活性在转运的电位依赖性激活方面没有表现出饱和。
