Calcium-Sensitive Chloride Channels in Vascular Smooth Muscle Cells

Abstract

Chloride (Cl-) channels were characterized in vascular smooth muscle cells (VSMC) using radioisotope flux and patch-clamp electrophysiological techniques. Transmembrane 125iodine (125I) efflux from subcultured (Passage 1-5) rat aortic VSMCs was used as an indicator of Cl- movements to study the relationship between intracellular calcium concentration ([Ca2+]i) and Cl- channel activity. Angiotensin II (Ang II) (10(-7) M) and adenosine 5'-triphosphate (ATP) (10(-4) M) induced rapid increases (9.7- and 14.9-fold, respectively) in 125I efflux rates. We found that both Ang II- and ATP-stimulated 125I efflux and [Ca2+]i increases were completely abolished after brief incubation (20 microM, 20 min) with the acetoxymethyl ester of 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM), a membrane-permeable Ca2+ chelator. However, when external EGTA was used to blunt agonist-stimulated Ca2+ influx, 125I efflux was still increased in response to Ang II and ATP. These data suggest that Ca2+ release from intracellular sites is sufficient to activate Cl- channels in response to Ang II and ATP. Using standard patch-clamp electrophysiological techniques, we found that Ang II, a Ca(2+)-mobilizing agonist, stimulated outward Cl- currents (gCl = 75 pS) in cell-attached (C/A) patches of primary and subcultured VSMCs. Collectively, these data suggest that Ang II and other vasoconstrictor agents stimulate Cl- channel activity via increases in [Ca2+]i. Cl- channel activation may help to depolarize the VSMC membrane leading to increased Ca2+ influx during agonist stimulation.

Chlorotoxin‐sensitive Ca2+‐activated Cl− channel in type R2 reactive astrocytes from adult rat brain

“…Most Cl Ca channels, including those of the CLCA gene family, exhibit small conductances in the range of 2-30 pS (Kidd and Thorn, 2000). In addition to these small-to moderate-conductance channels, larger-conductance Cl Ca channels have also been described in some preparations (Alton et al, 1991;Valkanov et al, 1994;Fahmi et al, 1995;White et al, 1995;Kourie et al, 1996;Hallani et al, 1998;Frings et al, 2000). A maxi-anion channel of ϳ 200 pS that is activated by Ca 2ϩ has been reported infrequently in mammalian cells (Lindau and Fernandez, 1986;Light et al, 1990;Kawahara and Takuwa, 1991), but not in mammalian neurons or astrocytes.…”

Torasemide Inhibits Angiotensin II–Induced Vasoconstriction and Intracellular Calcium Increase in the Aorta of Spontaneously Hypertensive Rats

“…16 This process would drive the opening of voltage-gated Ca 2ϩ channels, Ca 2ϩ influx, and vasoconstriction. 35 It has been shown that torasemide inhibits Cl Ϫ conductance in epithelial cells. 10 Interestingly, sulfonic derivatives have been shown to block Cl Ϫ channels in VSMCs from the rat aorta.…”

Regulation of the Cystic Fibrosis Transmembrane Conductance Regulator Channel by β-Adrenergic Agonists and Vasoactive Intestinal Peptide in Rat Smooth Muscle Cells and Its Role in Vasorelaxation

“…Effect of Angiotensin II on Iodide Efflux in Isolated SMC-In rat vascular smooth muscle cells, angiotensin II (AgII) is a vasoconstrictor agent that stimulates calcium-dependent chloride channel via increases in [Ca 2ϩ ] i (28,29). We therefore investigated whether calcium-dependent iodide efflux could be activated in SMC.…”