Effect of propionyl-L-carnitine on mechanical function of isolated rabbit heart

We studied the acute and chronic effects of propionyl-L-carnitine (PLC) on mechanical function of isolated rabbit heart. Propionyl-L-carnitine was either directly delivered in the perfusate (10^-9 to 10^-3 M) or intraperitoneally injected (250 mg/kg) for 10 days to the animals. When added acutely, propionyl-L-carnitine had no effect on inotropism, heart rate, or coronary perfusion pressure. When added chronically, propionyl-L-carnitine induced a positive inotropic effect, with no changes in heart rate or in coronary perfusion pressure, and it ameliorated the pressure-volume relationship. This effect of propionyl-L-carnitine was independent of the calcium concentration of the perfusion medium, but it was correlated with an increase in the myocardial content of propionyl-L-carnitine. The effect was not apparent after 5 days of treatment, although the tissue content of propionyl-L-carnitine remained unchanged. These data suggest that propionyl-L-carnitine, when given chronically, exerts a positive inotropic effect.