Activation of Ca2+-activated Cl- channels by store-operated Ca2+ entry in arterial smooth muscle cells does not require reverse-mode Na+/Ca2+ exchange.
The main purpose of this study was to characterize the stimulation of Ca(2+)-activated Cl(-) (Cl(Ca)) by store-operated Ca(2+) entry (SOCE) channels in rabbit pulmonary arterial smooth muscle cells (PASMCs) and determine if this process requires reverse-mode Na(+)/Ca(2+) exchange (NCX). In whole-cell voltage clamped PASMCs incubated with 1 μmol/L nifedipine (Nif) to inhibit Ca(2+) channels, 30 μmol/L cyclopiazonic acid (CPA), a SERCA pump inhibitor, activated a nonselective cation conductance permeable to Na(+) (I(SOC)) during an initial 1-3 s step, ranging from-120 to +60 mV, and Ca(2+)-activated Cl(-) current (I(Cl(Ca))) during a second step to +90 mV that increased with the level of the preceding hyperpolarizing step. Niflumic acid (100 μmol/L), a Cl(Ca) channel blocker, abolished I(Cl(Ca)) but had no effect on I(SOC), whereas the I(SOC) blocker SKF-96365 (50 μmol/L) suppressed both currents. Dual patch clamp and Fluo-4 fluorescence measurements revealed the appearance of CPA-induced Ca(2+) transients of increasing magnitude with increasing hyperpolarizing steps, which correlated with I(Cl(Ca)) amplitude. The absence of Ca(2+) transients at positive potentials following a hyperpolarizing step combined with the observation that SOCE-stimulated I(Cl(Ca)) was unaffected by the NCX blocker KB-R7943 (1 μmol/L) suggest that the SOCE/Cl(Ca) interaction does not require reverse-mode NCX in our conditions.
School of Community Health Sciences, University of Nevada, Reno, 89557, USA.
Jeff E
JE
Angermann
Abigail S
AS
Forrest
Iain A
IA
Greenwood
Normand
N
Leblanc
D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D018118:Chloride Channels / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D011817:Rabbits; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D014966:Xanthenes / Q000494:pharmacology
D000814:Aniline Compounds; D018118:Chloride Channels; D002712:Chlorides; C409648:Fluo 4; D019831:Sodium-Calcium Exchanger; D014966:Xanthenes; D002118:Calcium