Effects of taurine on contractions of the porcine coronary artery

The actions and mechanisms of taurine on vascular contractions have been studied in the isolated porcine coronary artery. Taurine depressed histamine-, serotonin-, KCl- and CaCl2-induced contractions in a concentration-dependent manner, with maximal contractions being depressed by 43.4%, 46.2%, 33.3% and 43.3%, respectively. Taurine relaxed arterial rings that were precontracted by either 30 mM KCl or 0.3 μMU46619, a thromboxane A2 analog, in a concentration-dependent manner, and the maximal relaxations were 39.4% and 38.7%, respectively. The vasorelaxations were nearly abolished by pretreatment with either the inward rectifier K+ channel (KIR) inhibitor, BaCl2 or the ATP sensitive K+ channel (KATP) inhibitor, glibenclamide, and were attenuated by the Ca2+-activated K+ channel (KCa) inhibitor tetraethylammonium. Denudation of the endothelium, and treatment with the nitric oxide synthase inhibitor, L-NAME, the cyclooxygenase inhibitor, indomethacin, or the voltage gated K+ channel (KV) inhibitor 4-aminopyridine did not affect the relaxation. The present results show that taurine antagonizes and relaxes the contractions of the porcine coronary artery, and suggest that the activation of KIR,KATP and Kca may be involved in taurine-induced relaxation of the porcine coronary artery.