Effects And Mechanisms Of Taurine On Contractions Of Porcine Coronary Artery

OBJECTIVE: Taurine has been shown to reduce the blood pressure in hypertensive patients as well as in hypertensive rats. However, the mechanisms for those effects of taurine are still not fully understood. The main purpose of this study was to investigate the effects and mechanisms of taurine on the porcine coronary artery.METHODS: The left anterior descending coronary artery (1.92±0.22 mm in diameter) was carefully dissected and mounted. The isotonic tension of the ring was recorded with PowerLab system. The vasodilator effects of taurine in the presence or absence of specific inhibitor were assessed.RESULTS: Serotonin (30μM) and Histamine (30μM) produced an unsustained contraction. Preincubation with taurine (20, 39.2 and 76.8 mM) concentration-dependently diminished histamine- and serotonin-induced contractions. The maximal inhibitions were 43.42%±15.83%for histamine-induced, and 59.91%±2.61%for serotonin-induced contraction. Incubation with taurine 20, 39.2 and 76.8 mM depressed CaCl2-induced contraction by 19.80%±4.85%, 31.41%±5.61% and 40.50%±6.21%, respectively and increased the EC50 value of CaCl2 from 0.55 mM to 1.42, 2.04, 2.38 mM, respectively. Taurine 20~107.6 mM relaxed 30 mM KCl-induced contractions of porcine isolated coronary artery in a concentration-dependent manner, and the maximal relaxation was 39.43%±15.53 %. Denudation, inhibition of nitric oxide synthetase by L-NAME or inhibition of cyclooxygenase by indomethacin failed to affect taurine-induced relaxation. Preincubation with different K+ channel specific inhibitors had different action potency on taurine-induced relaxation. 1 mM TEA moderately diminished, 1 mM BaCl2 or 10μM glibenclamide nearly abolished, but 1 mM 4-aminopyridine failed to affect taurine-induced relaxation.Conclusions: The present results show that taurine antagonizes and relaxes contractions of porcine coronary artery. It is suggested that the relaxation is endothelium-independent, and the activation of KCa, KIR and KATP may be involved in the relaxtion.