Cardioprotection by ranolazine in perfused rat heart.

ABSTRACT

We used the isolated working rat model to evaluate the effect of therapeutic concentrations (5-10 µM) of ranolazine on contractile performance, oxygen consumption, irreversible ischemic injury, and sarcoplasmic reticulum (SR) function. Ischemic injury was induced by 30 minutes of global ischemia followed by 120 minutes of Langendorff reperfusion and evaluated on the basis of triphenyltetrazolium chloride staining. SR function was determined on the basis of [H]-ryanodine binding, the kinetics of calcium-induced calcium release, measured by quick filtration technique, and oxalate-supported calcium uptake. In working hearts, ranolazine significantly reduced oxygen consumption (P = 0.031), in the absence of significant changes in contractile performance, and decreased irreversible ischemic injury (P = 0.011), if administered either before ischemia-reperfusion (25.4% ± 4.7% vs. 42.7% ± 6.0%) or only at the time of reperfusion (20.2% ± 5.2% vs. 43.7% ± 9.9%). In SR experiments, treatment with ranolazine determined a significant reduction in [H]-ryanodine binding (P = 0.029), because of decreased binding site density (369 ± 9 vs. 405 ± 12 fmol/mg), and in the kinetics of SR calcium release (P = 0.011), whose rate constant was decreased, whereas active calcium uptake was not affected. Ranolazine effectiveness at reperfusion and its ability to module SR calcium release suggest that this drug might be particularly useful to induce cardioprotection during coronary revascularization interventions, although the relevance of the effects on calcium homeostasis remains to be determined.