Zharikov S I, Herrera H, Block E R
Department of Medicine, University of Florida College of Medicine, Gainesville, USA.
Am J Physiol. 1997 Jan;272(1 Pt 1):L78-84. doi: 10.1152/ajplung.1997.272.1.L78.
System y+ accounts for the majority of L-arginine transport by pulmonary artery endothelial cells (PAEC). Given that membrane potential is a driving force for transport via system y+, we examined the hypothesis that hypoxia inhibits this transport by decreasing membrane potential. Porcine PAEC or plasma membrane vesicles derived from these cells were exposed to normoxia (room air-5% CO2) or hypoxia (0% O2-95% N2-5% CO2). After exposure, L-[3H]arginine transport and/or accumulation of the lipophilic cation [3H]tetraphenylphosphonium, a quantitative sensor of changes in cell membrane potential, were measured. Hypoxia caused reversible time-dependent decrease in L-arginine transport and membrane potential in PAEC and in plasma membrane vesicles. Comparable decreases in membrane potential and L-arginine transport by PAEC were also observed after depolarization induced by KCl or ouabain. Hyperpolarization, induced by valinomycin, increased membrane potential and L-arginine transport in PAEC and plasma membrane vesicles. Valinomycin also prevented the hypoxia-mediated decreases in membrane potential and L-arginine transport in PAEC. These results indicate that hypoxia-induced plasma membrane depolarization is responsible for reduced L-arginine transport by system y+ in hypoxic porcine PAEC.
y+系统介导肺动脉内皮细胞（PAEC）对L-精氨酸的大部分转运。鉴于膜电位是通过y+系统进行转运的驱动力，我们检验了以下假说：缺氧通过降低膜电位来抑制这种转运。将猪PAEC或源自这些细胞的质膜囊泡暴露于常氧（室内空气-5%二氧化碳）或缺氧（0%氧气-95%氮气-5%二氧化碳）环境。暴露后，测量L-[3H]精氨酸转运和/或亲脂性阳离子[3H]四苯基鏻的积累，后者是细胞膜电位变化的定量传感器。缺氧导致PAEC和质膜囊泡中L-精氨酸转运和膜电位出现可逆的时间依赖性降低。在氯化钾或哇巴因诱导去极化后，也观察到PAEC的膜电位和L-精氨酸转运出现类似程度的降低。缬氨霉素诱导的超极化增加了PAEC和质膜囊泡中的膜电位和L-精氨酸转运。缬氨霉素还可防止缺氧介导的PAEC膜电位和L-精氨酸转运降低。这些结果表明，缺氧诱导的质膜去极化是缺氧猪PAEC中y+系统介导的L-精氨酸转运减少的原因。
