Vasodilator effect of gaseous sulfur dioxide and regulation of its level by Acli in rat vascular tissues

摘要

To explore the toxicological and physiological role of gaseous SO_2 on vascular contractility and its level in vascular tissues, a vasodilation study of isolated rat thoracic aortic rings by gaseous SO_2 was carried out. The level of SO_2 in vascular tissue was assayed using a modified high-performance liquid chromatographic method with fluorescence detection (HPLC-FD). The results show that gaseous SO_2 (from 1 muW to 2000 muM) relaxed rat thoracic aortic rings in a dose-dependent manner. The physiological concentrations of SO_2 in thoracic aortic tissues and plasma in rats were 127.76±31.34 muM and 16.77±8.24 muW, respectively; The vasorelaxant effect of gaseous SO_2 at physiological and low concentrations (<450 uM) was endothelium dependent, and at high concentrations (>500 muW) was endothelium independent. The results also show that SO_2 could be endogenously generated in vascular tissues, and mainly in vascular endothelial cells; acetylcholine (Ach) increased the SO_2 level in vascular tissue, and no adrenaline (NE) decreased the SO_2 level. These findings demonstrate that gaseous SO_2 is a vasorelaxant substance, and the vasorelaxant effect of gaseous SO_2 is much stronger than that of its derivatives sulfite and bisulfite, which result from the inactivation process of SO_2 gas transmitter by which SO_2 is hydrated to form sulfite, and the latter is enzymatically oxidized to form sulfate.These findings also demonstrate that endogenous SO_2 level in vascular tissue may be regulated by Ach and NE.