Vasomotion has chloride-dependency in rat mesenteric small arteries

摘要

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,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 [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 SCN− _o. 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.