Modulations by taurine of the spontaneous action potentials in right atrial muscles of rats.
1. Effects of taurine on the spontaneous action potentials in right atrial muscles of rats were examined using a conventional microelectrode method at 36 degrees C, and at different extracellular Ca2+ concentrations ([Ca]o). 2. When [Ca]o was 1.8 mM, taurine (10 and 20 mM) increased the sinus rate in a concentration-dependent manner. On the other hand, in 5.4 mM [Ca]o solution, 10 mM taurine also increased the sinus rate, but at 20 mM decreased it. 3. Taurine (20 mM) at 1.8 mM [Ca]o decreased the action potential duration, but at 5.4 mM [Ca]o increased it. Other action potential parameters were not altered to a significant extent. 4. In addition, at 5.4 mM [Ca]o, taurine at 10 mM elicited dysrhythmias such as bigeminy, and at 20 mM depressed the spontaneous action potentials and prolonged cycle length. 5. These results indicate that taurine caused a positive chronotropic effect at both [Ca]o levels; however, at 5.4 mM [Ca]o, taurine (20 mM) reversed the positive to a negative chronotropic effect, presumably resulting in the development of cellular calcium overload.
Satoh
H
H
Department of Pharmacology, Nara Medical University, Kashihara, Japan. hysat@naramed-u.ac.jp
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D016275:Atrial Function; D002118:Calcium / Q000378:metabolism; D006325:Heart Atria / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D051381:Rats; D013654:Taurine / Q000494:pharmacology*
D013654:Taurine; D002118:Calcium