title: FCCP depolarizes plasma membrane potential by activating proton and Na+ currents in bovine aortic endothelial cells.
abstract: We investigated the effects of carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), a protonophore and uncoupler of mitochondrial oxidative phosphorylation in mitochondria, on plasma membrane potential and ionic currents in bovine aortic endothelial cells (BAECs). The membrane potential and ionic currents of BAECs were recorded using the patch-clamp technique in current-clamp and voltage-clamp modes, respectively. FCCP activated ionic currents and depolarized the plasma membrane potential in a dose-dependent manner. Neither the removal of extracellular Ca2+ nor pretreatment with BAPTA/AM affected the FCCP-induced currents, implying that the currents are not associated with the FCCP-induced intracellular [Ca2+]i increase. FCCP-induced currents were significantly influenced by the changes in extracellular or intracellular pH; the increased proton gradient produced by lowering the extracellular pH or intracellular alkalinization augmented the changes in membrane potential and ionic currents caused by FCCP. FCCP-induced currents were significantly reduced under extracellular Na+-free conditions. The reversal potentials of FCCP-induced currents under Na+-free conditions were well fitted to the calculated equilibrium potential for protons. Interestingly, FCCP-induced Na+ transport (subtracted currents, I(control)- I(Na+-free) was closely dependent on extracellular pH, whereas FCCP-induced H+transport was not significantly affected by the absence of Na+. These results suggest that the FCCP-induced ionic currents and depolarization, which are strongly dependent on the plasmalemmal proton gradient, are likely to be mediated by both H+ and Na+ currents across the plasma membrane. The relationship between H+ and Na+ transport still needs to be determined.
authors.affiliation: Division of Metabolic Disease, Dept. of Biomedical Sciences, National Institute of Health, 5 Nokbun-Dong, Eunpyung-Ku, Seoul 122-701, Korea.
authors.forename: Kyu-Sang
authors.initials: KS
authors.lastname: Park
authors.forename: Inho
authors.initials: I
authors.lastname: Jo
authors.forename: Kim
authors.initials: K
authors.lastname: Pak
authors.forename: Sung-Won
authors.initials: SW
authors.lastname: Bae
authors.forename: Hyewhon
authors.initials: H
authors.lastname: Rhim
authors.forename: Suk-Hyo
authors.initials: SH
authors.lastname: Suh
authors.forename: Jin
authors.initials: J
authors.lastname: Park
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
authors.forename: Insuk
authors.initials: I
authors.lastname: So
authors.forename: Ki Whan
authors.initials: KW
authors.lastname: Kim
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology; D002118:Calcium / Q000378:metabolism; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology*; D002412:Cations / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects* / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D011522:Protons; D012964:Sodium / Q000378:metabolism*
chemical_list: D002412:Cations; D007476:Ionophores; D011522:Protons; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D012964:Sodium; D011188:Potassium; D002118:Calcium