Effects of taurine on slow action potentials in papillary muscles of guinea pig.

AIM To examine the effects of taurine on the slow action potentials induced by KCl 24 mmol.L(-1) or tetrodotoxin 40 mumol.L(-1) in guinea pig papillary muscles. METHODS The transmembrane AP was recorded by a conventional glass microelectrode filled with KCl 3 mmol.L(-1). The muscles were exposed to high K(+)-Tyrode's solution or perfused with Tyrode's solution containing tetrodotoxin. Ouabain was added in order to induce oscillatory afterpotentials. RESULTS Taurine 20 mmol.L(-1) decreased the maximal upstroke velocity of slow action potential and prolonged the action potential duration at 50% of repolarization. The amplitude of slow action potential and the maximal upstroke velocity both increased by CaCl(2)3 mmol.L(-1) were antagonized by taurine. Taurine increased the concentration of ouabain for oscillatory afterpotential and prolonged the onset time of oscillatory afterpotential. CONCLUSION Taurine possesses a calcium antagonistic property.