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Activation of Ca2+-activated Cl channels by store-operated Ca2+ entry in arterial smooth muscle cells does not require reverse-mode Na+/Ca2+ exchange

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The main purpose of this study was to characterize the stimulation of Ca2+-activated Cl (ClCa) by store-operated Ca2+ entry (SOCE) channels in rabbit pulmonary arterial smooth muscle cells (PASMCs) and determine if this process requires reverse-mode Na+/Ca2+ exchange (NCX). In whole-cell voltage clamped PASMCs incubated with 1 μmol/L nifedipine (Nif) to inhibit Ca2+ channels, 30 μmol/L cyclopiazonic acid (CPA), a SERCA pump inhibitor, activated a nonselective cation conductance permeable to Na+ (ISOC) during an initial 1–3 s step, ranging from–120 to +60 mV, and Ca2+-activated Cl current (ICl(Ca)) during a second step to +90 mV that increased with the level of the preceding hyperpolarizing step. Niflumic acid (100 μmol/L), a ClCa channel blocker, abolished ICl(Ca) but had no effect on ISOC, whereas the ISOC blocker SKF-96365 (50 μmol/L) suppressed both currents. Dual patch clamp and Fluo-4 fluorescence measurements revealed the appearance of CPA-induced Ca2+ transients of increasing magnitude with increasing hyperpolarizing steps, which correlated with ICl(Ca) amplitude. The absence of Ca2+ transients at positive potentials following a hyperpolarizing step combined with the observation that SOCE-stimulated ICl(Ca) was unaffected by the NCX blocker KB-R7943 (1 μmol/L) suggest that the SOCE/ClCa interaction does not require reverse-mode NCX in our conditions.
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Keywords: calcium-activated chloride channels; canaux chloriques activés par le calcium; cellules de muscle lisse vasculaire; entrée de Ca2+ induite par vidange du reticulum sarcoplasmique (SOCE); hypertension pulmonaire; pulmonary hypertension; sodium-calcium exchange; store-operated calcium entry; vascular smooth muscle cells; échange sodium-calcium

Document Type: Research Article

Affiliations: 1: School of Community Health Sciences, University of Nevada, Reno, 1664 North Virginia, Reno, NV 89557, USA 2: Department of Pharmacology, Center for Molecular Medicine, University of Nevada School of Medicine, 1664 North Virginia, Reno, NV 89557-0270, USA. 3: Division of Basic Medical Sciences, St George’s University of London, Cranmer Terrace, London, UK SW17 0RE

Publication date: July 4, 2012

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