Tretter L, Chinopoulos C, Adam-Vizi V
Department of Medical Biochemistry, Neurochemical Group, Semmelweis University of Medicine, Budapest, Hungary.
Mol Pharmacol. 1998 Apr;53(4):734-41. doi: 10.1124/mol.53.4.734.
The effect of the protonophore carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazon (FCCP) was studied on the intracellular [Na+], pH, and plasma membrane potential in isolated nerve terminals. FCCP induced a rise of [Na+]i at, and even below, the concentrations (0.025-1 microM) in which it is usually used in intact cells to eliminate Ca2+ uptake by mitochondria. The FCCP-induced increase of [Na+]i correlates with a fall in both the ATP level and the ATP/ADP ratio. In addition, a sudden rise of the intracellular proton concentration ([H+]i) from 83 +/- 0.4 to 124 +/- 0.7 nM was observed on the addition of FCCP (1 microM). Parallel with the rise in [H+]i, an abrupt depolarization was detected, followed by a slower decrease in the plasma membrane potential. Both the extent of the pHi change and the fast depolarization of the plasma membrane were proportional to the proton electrochemical gradient across the plasma membrane; when this gradient was increased, greater depolarization was detected. The slower decrease of the membrane potential after the fast initial depolarization was abolished when the medium contained no Na+. It is concluded that FCCP (1) gives rise to a depolarization by setting the plasma membrane potential close to the proton equilibrium potential and (2) enhances the intracellular [Na+] as a consequence of an insufficient ATP level and ATP/ADP ratio to fuel the Na+,K+/ATPase. Because both disturbed Na+ homeostasis and plasma membrane depolarization could profoundly interfere with Ca2+ homeostasis in the presence of protonophores, consideration given to these alterations may help to clarify the cellular Ca2+ sequestration processes.
研究了质子载体羰基氰化物 - 对 - 三氟甲氧基苯基腙（FCCP）对分离神经末梢细胞内[Na⁺]、pH值和质膜电位的影响。FCCP在其通常用于完整细胞以消除线粒体对Ca²⁺摄取的浓度（0.025 - 1微摩尔）时，甚至在该浓度以下，都会诱导细胞内[Na⁺]升高。FCCP诱导的[Na⁺]升高与ATP水平和ATP/ADP比值的下降相关。此外，加入FCCP（1微摩尔）后，观察到细胞内质子浓度（[H⁺]）从83±0.4纳摩尔突然升至124±0.7纳摩尔。随着[H⁺]升高，检测到质膜突然去极化，随后质膜电位缓慢下降。pHi变化的程度和质膜的快速去极化都与跨质膜的质子电化学梯度成正比；当该梯度增加时，检测到更大程度的去极化。当培养基中不含Na⁺时，快速初始去极化后膜电位的缓慢下降被消除。得出的结论是，FCCP（1）通过使质膜电位接近质子平衡电位而导致去极化，（2）由于ATP水平和ATP/ADP比值不足以驱动Na⁺，K⁺/ATP酶，从而导致细胞内[Na⁺]升高。由于在存在质子载体的情况下，Na⁺稳态紊乱和质膜去极化都可能深刻干扰Ca²⁺稳态，考虑这些改变可能有助于阐明细胞Ca²⁺螯合过程。
