Functional and binding evidence of taurine inhibition of alpha-adrenoceptor effects on guinea-pig ventricle.
The effect of taurine on alpha- and beta-mediated positive inotropic effects was investigated in guinea-pig ventricular strips. Loading with taurine dose-dependently antagonized the phenylephrine-induced positive inotropic effect while it was ineffective on beta-mediated positive inotropic effect. The superfusion with a taurine-free medium determined a loss of intracellular taurine, while the loading with 20 mM taurine prevented this depletion. Preincubation of cardiac membranes with different concentrations of taurine (1 to 20 mM) decreased 3H-prazosin binding, and the saturation curve obtained after preincubation of cardiac membranes with 20 mM taurine showed that taurine had a more marked effect on the number of binding sites. In both experimental models, beta-alanine did not mimic any taurine effects, suggesting that taurine actions might be specific.
D000818:Animals; D001667:Binding, Competitive; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D013654:Taurine / Q000494:pharmacology*; D016276:Ventricular Function; D015091:beta-Alanine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D015091:beta-Alanine; D013654:Taurine; D010656:Phenylephrine; D011433:Propranolol; D011224:Prazosin