Vasoconstrictive Effect And Mechanisms Of Taurine In Rat Abdominal Aortas

Objective: To investigate the vasoconstrictive effect and the possible mechanisms of taurine in abdominal aortas of rats.Methods: Isotonic tension of rat isolated abdominal aortic ring was recorded with Powerlab system. The effect of taurine on the basic tone of the ring was observed and the mechanisms were assessed by studying the influences of various drugs with well known mechanism on the effect of taurine in the endothelium intact rings or endothelium denudated rings.Results: Taurine (20-120 mmol/L) caused concentration-dependent contraction in abdominal aortas with or without endothelium and the contraction was greater in the endothelium denudated rings. The contraction in the presence of L-NAME(0.1mmol/L) was significantly greater than that in the absence of L-NAME. Tetraethtylamine (10mmol/L), an antagonist of calcium activated potassium channels (K_Ca), and glibenclamide(10μmol/L), an antagonist of ATP sensitive potassium channels (K_ATP) enhanced the vasoconstriction of taurine, but 4-aminopyridine (1mmol/L)and BaCl₂(0.1mmol/L) had no significant effects on the vasoconstriction of taurine. And taurine (120 mmol/L) produced a sustained contraction in Ca⁺-free HEPES and a further sustained contraction on the recovery of extracellular 3.0 mmol/L. There were no significant differences among the contractions induced by taurine in the absence or the presence of one of following inhibitors: propranolol (1μmol/L), phentolamine (1μmol/L), nimodipine (0.01μmol/L), atropine (0.1μmol/L) diphenhydramine (1μmol/L) andβ-Alanine(60mol/L).Conclusions: Taurine caused concentration-dependent contraction in rat isolated abdominal aortic ring, the effect is enhanced by endothelium denudation, NO synthesis inhibition; KB_Ca and K_ATP inhibition and the contraction was on the dependence of intracellular Ca²⁺ release and extracellular Ca²⁺ influx.