Bussolati O, Laris P C, Nucci F A, Dall'Asta V, Longo N, Guidotti G G, Gazzola G C
Am J Physiol. 1987 Sep;253(3 Pt 1):C391-7. doi: 10.1152/ajpcell.1987.253.3.C391.
The cell-to-medium distribution ratios at steady state of L-arginine (RArg) and of the lipid-soluble cation tetraphenylphosphonium (RTPP) were studied as a function of the membrane potential (Em) in adult human fibroblasts. The relationship between RArg and Em was qualitatively similar to that of RTPP and Em. Quantitatively, RArg and RTPP differed in that 1) RTPP was much greater than RArg when Em was near zero, indicating a significant binding component in the uptake of TPP+ but not of L-arginine, and 2) after a correction for binding when Em is near zero, RTPP was still greater than RArg so that RT/F . ln RTPP exceeded RT/F . ln RArg by 10-25 mV. The pattern of the redistribution of accumulated TPP+ and arginine after an alteration of Em was identical. In null-point experiments, the external [K+] for which there were no changes in cellular TPP+ or L-arginine in the presence of high valinomycin (the null points) were very similar for the two probes. Em calculated from the null-point measurements (-70(-)-80 mV) was also very similar to RT/F . ln RArg and thus smaller than RT/F.ln RTPP. It was concluded that 1) there was an additional TPP+ binding as cellular [TPP] rose in response to more negative membrane potentials, 2) the transport system for L-arginine in these cells (system y+) operates as a facilitated diffusion system driven by the membrane potential, and 3) in some circumstances, L-arginine could be employed as a probe of Em.
在成人人类成纤维细胞中，研究了L-精氨酸（RArg）和脂溶性阳离子四苯基鏻（RTPP）在稳态下的细胞-培养基分配比与膜电位（Em）的关系。RArg与Em的关系在定性上与RTPP和Em的关系相似。在定量方面，RArg和RTPP的不同之处在于：1）当Em接近零时，RTPP远大于RArg，这表明TPP+摄取中有显著的结合成分，而L-精氨酸摄取中没有；2）在对Em接近零时的结合进行校正后，RTPP仍然大于RArg，因此RT/F·ln RTPP比RT/F·ln RArg高出10 - 25 mV。Em改变后，积累的TPP+和精氨酸的重新分布模式是相同的。在零点位实验中，对于这两种探针，在高缬氨霉素存在下细胞TPP+或L-精氨酸没有变化时的外部[K+]（零点位）非常相似。根据零点位测量计算出的Em（-70（-）-80 mV）也与RT/F·ln RArg非常相似，因此小于RT/F·ln RTPP。得出的结论是：1）随着膜电位变得更负，细胞内[TPP]升高时存在额外的TPP+结合；2）这些细胞中L-精氨酸的转运系统（系统y+）作为由膜电位驱动的易化扩散系统发挥作用；3）在某些情况下，L-精氨酸可作为Em的探针。
