Vasodilation And Mechanism Of Action Of Taurine On Rat Pulmonary Artery Ring

OBJECTIVE: To investigate the vasodilative roles and the possible mechanisms of taurine on rat pulmonary artery ring.METHODS: Carefully dissected the third branch of pulmonary artery ring (vessel diameter: 0.50±0.12mm), Using DMT small vessels records system records the changes in vascular tone. The relaxation responses of taurine to KCl preconstricted rings were recorded. The inhibitors of eNOS(N-nitro-L-arginine methyl ester), cyclooxygenase(Indometacin), potassium channels blockers were used to study on the relaxation effect of taurine. Norepinephrine and Potassium chloride were used to observe if the constriction was affected by taurine which was pre-incubated in advance.RESULTS: Taurine (20~80mmol·L-1) caused concentration-dependent relaxation in pulmonary artery; NG-nitro-L-arginine methyl ester (0.1mmol·L-1) and indomethacin (10μmol·L-1) did not significantly affected taurine induced relaxation; But Glibenclamide(10μmol·L-1), an antagonist of ATP sensitive potassium channels(KATP), and tetraethtylamine(10mmol·L-1) , an antagonist of calcium activated potassium channels(KCa) can significantly inhibit the vasorelaxing action of taurine on pulmonary arteries precontracted by KCl. Barium chloride (1mmol·L-1), an antagonist of Inward rectifier potassium channel (KIR), and 4-aminopyridine (1mmol·L-1), an antagonist of Voltage-Dependent K+ channels (KV) did not significantly affected taurine induced relaxation. And taurine (20~80mmol·L-1) concentration dependently shifted the concentration–contraction curves to KCl to the right in a nonparallel manner with the maximal contraction depressed; In the calcium-less PSS (complexed by EGTA), after taurine with different concentration (20~80mmol·L-1) was preincubated respectively, NE (10μmol·L-1)could make a rapid and transient constriction was added subsequently; Compared with the controlled group, taurine (20~80mmol·L-1) could significantly reduce the constriction effect induced by NE (P<0.05).CONCLUSION: 1. The vasorelaxing action of taurine is concentration-dependent; 2. It is suggested that KCa and KATP may be involved in the relaxtion,not KV or KIR. ;3. The relaxation function of taurine on vessel smooth muscle don't result from the endothelium; 4. Taurine had a certain inhibition effect of the constriction induced by potassium chloride; 5. Taurine could produce a vascular relaxation effect on rat pulmonary artery ring induced by Norepinephrine.