Vasodilative effect and mechanism of taurine on thoracic aorta of rats

AIM To investigate the vasodilative roles and the possible mechanisms of taurine on thoracic aorta of rats. METHODS Isotonic tension of thoracic aortic rings precontracted by phenylephrine (PE, 1 μmol·L~ -1 ) or KCl (60 mmol·L~ -1 ) was recorded. The vasorelaxing action of taurine and the influence of various drugs on it were observed in the rings with endothelium intact or endothelium denuded. RESULTS Taurine (20-80 mmol·L~ -1 ) caused concentration-dependent relaxation in thoracic aortas with or without endothelium, and there was no significant difference between them. N~G-nitro-L-arginine methyl ester (0.1 mmol·L~ -1 ) had no effect on the vasorelaxing action of taurine on thoracic aortas precontracted by PE or KCl. β-Alanine (60 mmol·L~ -1 ) diminished the vasorelaxing action of taurine in KCl-precontracted rings, but enhanced the action in PE-precontracted rings. Tetraethylamine, an antagonist of calcium activated potassium channels (KB_ Ca ), and glibenclamide, an antagonist of ATP sensitive potassium channels (K_ ATP ) attenuated the vasorelaxing effect of taurine, but 4-aminopyridine and BaCl_2 had no significant effect on the vasorelaxing action of taurine. CONCLUSION The vasorelaxing action of taurine is endothelium-independent and associated with taurine transmembrane transportation; KB_ Ca and K_ ATP may be involved in the action of taurine.