Vasomotion has chloride-dependency in rat mesenteric small arteries

The possibility that Ca2+-activated Cl(-)conductances (CaCCs) contribute to oscillations in vascular tone (vasomotion) is tested in isolated mesenteric small arteries from rats where cGMP independent (I-Cl(Ca)) and cGMP-dependent (I-Cl(Ca,I-cGMP)) chloride conductances are important. The effect of anion substitution and Cl- channel blockers on noradrenaline (NA)-stimulated tension in isometrically mounted mesenteric arteries and for chloride conductance of smooth muscle cells isolated from these arteries were assessed electrophysiologically. Cl-o(-) replacement with aspartate blocked vasomotion while 36mM SCNo- (substituted for Cl-) was sufficient to inhibit vasomotion. Oscillations in tone, membrane potential, and [Ca2+](i) disappeared with 36mM SCN-. DIDS and Zn2+ blocked I-Cl((Ca,cGMP)) but not I-Cl((Ca)). Vasomotion was not sensitive to DIDS and Zn2+, and DIDS and Zn2+ induce vasomotion in arteries without endothelium. The vasomotion in the presence of DIDS and Zn2+ was sensitive to 36mM SCNo-. The anion substitution data indicate that Cl- is crucial for the V-m and [Ca2+](i) oscillations underlying vasomotion. The Cl- channel blocker data are consistent with both CaCCs being important.