The cardioprotective effect of the two synthetic carnitine derivatives, propionylcarnitine taurine amide (PCTA) and butyrylcarnitine taurine amide (BCTA), were studied in isolated perfused rat hearts. The protective effects of PCTA and BCTA were compared with those of chemically similar compounds, which have already been investigated in part and reported on; i.e. propionylcarnitine, carnitine, taurine and the combination of propionylcarnitine and taurine. The addition of either PCTA or BCTA significantly improved the recovery of cardiac function of ischemic reperfused hearts. PCTA (0.5 mM) treated hearts regained 75%, 91% and 89% of their preischemic values for cardiac output, left ventricular pressure and dp/dt after 90 min ischemia and 15 min reperfusion. These parameters of cardiac function remained impaired in control hearts which recovered only 38% of the initial preischemic cardiac output, 73% of initial intraventricular developed pressure and 64% of initial positive dp/dt. The cardioprotective effects of PCTA, BCTA and propionylcarnitine were in the same range. However, PCTA and BCTA acted in 20-fold lower molar concentrations compared to propionylcarnitine. Carnitine (11 mM), taurine (11 mM) as well as the combination of propionylcarnitine and taurine at low concentrations had no cardioprotective effect in these experiments. Myocardial adenosine triphosphate (ATP) and creatine phosphate (CP) concentrations were significantly higher in the PCTA or BCTA treated hearts than in controls, and lactate levels were reduced.(ABSTRACT TRUNCATED AT 250 WORDS)