Oxidant stress activates a non-selective cation channel responsible for membrane depolarization in calf vascular endothelial cells.
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.
Koliwad
S K
SK
Department of Molecular Physiology, Baylor College of Medicine, Houston, TX 77030, USA.
Kunze
D L
DL
Elliott
S J
SJ
D000818:Animals; D002412:Cations / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D018384:Oxidative Stress / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010545:Peroxides / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000494:pharmacology*; D020122:tert-Butylhydroperoxide
D002412:Cations; D007473:Ion Channels; D010545:Peroxides; D017382:Reactive Oxygen Species; D020122:tert-Butylhydroperoxide