Vasomotion has chloride-dependency in rat mesenteric small arteries

The possibility that Ca 2+ -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,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 SCN − o (substituted for Cl − ) was sufficient to inhibit vasomotion. Oscillations in tone, membrane potential, and [Ca 2+ ] i disappeared with 36mM SCN − . DIDS and Zn 2+ blocked I Cl(Ca,cGMP) but not I Cl(Ca) . Vasomotion was not sensitive to DIDS and Zn 2+ , and DIDS and Zn 2+ induce vasomotion in arteries without endothelium. The vasomotion in the presence of DIDS and Zn 2+ was sensitive to 36mM SCN − o . The anion substitution data indicate that Cl − is crucial for the V m and [Ca 2+ ] i oscillations underlying vasomotion. The Cl − channel blocker data are consistent with both CaCCs being important.