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Ethanol induced relaxation of rat thoracic aorta at different resting tension and its possible mechanism

The aim of this study was to investigate the vascular effect of ethanol on rat aorta at different resting tension and its underlying mechanism. The tension of the isolated Sprague‐Dawley rat thoracic aortic rings perfused with different concentrations of ethanol was measured using organ bath technique. At different resting tension (1.0 – 4.0 g), ethanol (0.1 – 7.0 ‰) caused a concentration‐dependent relaxation on endothelium‐denuded aortic rings precontracted with KCl (6×10−2 mol/L) or phenylephrine (PE, 10−6 mol/L), and the vasodilating effect was the most potent when the aortic rings was at the resting tension of 3 g. Ethanol inhibited the CaCl2 induced contraction and downward shifted concentration‐response curve of endothelium‐denuded aortic rings precontracted with KCl or PE. Incubation of aorta with ruthenium red (10−5 mol/L) or heparin (50 mg/L) decreased the vasodilating effect of ethanol. The results indicate that endothelium‐independent relaxation induced by ethanol is concerned with the resting tension. This effect of ethanol may be mediated by the inhibition of voltage‐dependent and receptor‐operated Ca2+ channels in the vascular smooth muscle cells as well as the inhibition of the intracellular ryanodine receptor and IP3 pathway.