Effects of taurine on the transmembrane ionic currents of rat and guinea pig ventricular fibres.

The effects of taurine on electrical properties of isolated myocardial ventricular fibres were studied in rat and guinea pig. The action potential amplitude was decreased in these species while the plateau and the repolarization phase were not altered. This suggests that simple inspection of the plateau phase is not sensitive enough to pick up changes in outward current since voltage clamp experiments showed that taurine decreased both potassium current and fast inward current. However, the slow inward calcium current remained unchanged with taurine in each species. These results suggest that the inotropic effects of taurine on rat and guinea pig heart contraction already described, were not due to modifications of the cell membrane permeability for calcium. It seems more reasonable to assume that the cardiac actions of this compound result from intracellular changes in calcium availability.