Oxidant stress activates a non-selective cation channel responsible for membrane depolarization in calf vascular endothelial cells

• Published in: The Journal of physiology 1996-02, Vol.491 (Pt 1), p.1-12
• Main Authors: Koliwad, S K, Kunze, D L, Elliott, S J
• Format: Article
• Language: English
• Subjects: Animals; Cations - metabolism; Cattle; Cell Membrane - drug effects; Cell Membrane - physiology; Cell Membrane Permeability - drug effects; Electrophysiology; Endothelium, Vascular - cytology; Endothelium, Vascular - metabolism; Ion Channel Gating - drug effects; Ion Channel Gating - physiology; Ion Channels - metabolism; Membrane Potentials - physiology; Oxidative Stress - physiology; Patch-Clamp Techniques; Peroxides - pharmacology; Reactive Oxygen Species - pharmacology; tert-Butylhydroperoxide
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1996.sp021191

1. In vascular endothelial cells, oxidant stress increases cell Na+ content and inhibits the agonist-stimulated influx of external Ca2+. Further, oxidant stress increases uptake of Ca2+ into otherwise quiescent endothelial cells. To determine the mechanism responsible for altered Na+ and Ca2+ homeostasis, the present study examined the effect of oxidant stress on ionic current and channel activity in calf pulmonary artery endothelial cells. 2. Voltage-clamped control cells had a zero-current potential of -60 mV. Incubation of cells with the oxidant tert-butylhydroperoxide (tBuOOH; 0.4 mM, 1 h) caused depolarization to -4 mV and activation of ionic current equally selective for Na+ and K+. 3. Cell-attached membrane patches made on tBuOOH-treated cells contained ion channels that had a bidirectional conductance of 30 pS and that were not present in patches from control cells. Inside-out patches excised from oxidant-treated cells showed the channel to be equally selective for Na+ and K+ and to allow inward Ca2+ current. 4. Oxidant-activated channels were observed to display two gating modalities that were further evident during analysis of single-channel open probability. Neither modality was significantly affected by altering internal [Ca2+] (1 microM-10 nM). 5. Activation of non-selective channels provides a possible mechanism by which oxidants may increase endothelial cell Na+ content. Channel permeability to Ca2+ may account in part for the elevation of cytosolic free [Ca2+] that occurs in oxidant-treated cells. 6. Channel activation is associated with membrane depolarization, a mechanism that may contribute to oxidant inhibition of the agonist-stimulated Ca2+ influx pathway.