The aim of this study was to investigate the vasodilatory effects of aloperine, one of main alkaloid was extracted from Sophora alopecuroides, on rat isolated thoracic aortic rings and its possible mechanisms. The isolated aortic arteries from normotensive Sprague Dawley rats were precontracted with phenylephrine (1 × 10⁻⁶ M) or KCl (60 mM). Then, aloperine (3.44 × 10⁻³ – 17.21 × 10⁻³ M) was added cumulatively and the tension curves was observed and recorded. The changes in tension in both endothelium-intact and endothelium-denuded aortic rings were also recorded. Afterwards, the interaction between aloperine with NG-nitro-L-arginine methylester (0.1 mM), indomethacin (1 × 10⁻³ mM), tetraethylammonium (10 mM), 4-aminopyridine (5 mM), BaCl₂ (1 mM) and glibenclamide (0.01 mM) was evaluated. In this study, aloperine caused concentration-dependent relaxations in aortic rings precontracted with phenylephrine, but this effect was not observed in KCl-pretreated rings. Removal of endothelium showed no influence on vasodilatory effects of aloperine. In addition, preincubation with NG-nitro-L-arginine methylester and indomethacin did not inhibit the vasodilatory effects of aloperine, suggesting that the vasodilative action is endothelium-independent. Relaxant responses to aloperine were inhibited by tetraethylammonium and 4-aminopyridine. However, the vasorelaxant effect of aloperine was also not influenced by the preincubation with BaCl₂ and glibenclamide. These findings suggest that aloperine-induced vasorelaxation effects are mainly due to the operations of voltage-operated potassium channels and ATP-sensitive potassium channels.
Keywords: aloperine; ATP-sensitive potassium channels; endothelium independent; vasodilation; voltage-operated potassium channels.