The Effect Of Taurine On Vascular Reactivities In Isolated Porcine Coronary Arterial Rings

OBJECTIVE: To study the effects of taurine (Tau) on contractions or relaxations induced by several agents including potassium chloride (KCL), histamine (His), pituitrin (Pit), noradrenaline (NE), isoprenaline (Iso), aminophylline (Amin), nifedipine (Nif), verapamil (Ver), diltiazem (Dil) in isolated porcine coronary arterial rings respectively and to explore mechanism of Tau.METHODS: Isolated porcine coronary arterial rings were suspended in organ chambers, bathed in Krebs-solution at 37°C and gassed with 95% O2 and 5% CO2. The vascular tension was recorded with MS2000 computer system through pressure transducer.RESULTS: 1. When Tau (5-80mmol/L) was added accumulatively into the bath, less than 5% change of resting tension on isolated porcine coronary arterial ring was observed. 2. Preincubition with 40mmol/L Tau significantly decreased KCL (30mmol/L)- and Pit (2U/L)-induced contractions by 11.23±3.64% and 5.53±2.72% respectively, but did not significantly affect NE (10-6mol/L)- and His (10-5mol/L)-induced contractions. 3. Tau 20-60mmol/L concentration- dependently caused the rightward shifting of KCL concentration-response curves with the maximal response depressed. 4. Tau 20-60mmol/L concentration- dependently caused the rightward shifting of Pit concentration-response curves with the maximal response unaffected. 5. In free-Ca2+ Krebs solution, Ca2+ produced contractile action. Maximal contraction was reached at 4mmol/L Ca2+, with an Emax being 159.42±8.23%, and arterial rings appeared relaxation with further higher Ca2+ concentrations. 6. Tau 20, 40 and 60mmol/L made concentration-response curves of CaCL2 (0.5-5.5mmol/L)shifted rightward, with Emax reduced by 19.46±5.31%,31.16±6.15%,34.23±2.35% significantly. 7. Tau exerted a partly concentration-dependent vasodilator action in coronary arterial rings precontracted with 30mmol/L KCL, with maximal relaxation depressed by 15.04±3.05%. 8. In the rings precontracted with 30 mmol/L KCL, Iso (4.8μmol/L) or Amin (5.2μmol/L) or Nif (31.6mmol/L) or Ver (1.5μmol/L) or Dil (7.8μmol/L) produced relaxations, and coexistence with Tau 20-60mmol/L produced more potent relaxations.CONCLUSION: 1. Tau has no effect on resting tension. 2. It was selectively that tau exerted a concentration-dependent inhibition of contraction induced by KCL and Pit, but no effect on His and NE. 3. Tau can produced a concentration- dependent relaxation partly on isolated Coronary arterial rings precontracted by KCL. 4. Tau antagonized contraction induced by Ca2+ concentration-dependently within a concentration. 5. Tau increased relaxation of Iso or Amin or Nif or Ver or Dil in isolated Coronary arterial rings commonly. 6. Synergistic actions were existed between Tau and Ver or Dil in isolated Coronary arterial rings.