Taurine: effect on myocardial relaxation

1. The effects of taurine on cardiac inotropic state and relaxation were studied in the isolated rabbit heart using solutions containing three concentrations of calcium: 0.7, 1.8 and 3.0 mmol/l. 2. Increases in Ca2+ caused increases in inotropic indices, but had no effect on rate constant of relaxation. 3. Taurine had a positive inotropic effect at Ca2+ = 0.7 mmol/l, an equivocal effect at Ca2+ = 1.8 mmol/l and a negative inotropic effect at Ca2+ = 3.0 mmol/l. 4. Taurine had no effect on the rate constant of relaxation at any Ca2+ concentration. 5. Taurine modulates the positive inotropic effect of Ca2+ but neither taurine nor Ca2+ affect the rate constant of relaxation.