In this study, we aimed to compare the effects of low- and high-quality cardiopulmonary resuscitation (CPR) on cardioprotection by induced hypothermia (IH) at 34 °C and examine whether extracellular signal-regulated kinase or endothelial nitric oxide synthase mediates this cardioprotection. Left ventricle infarct sizes were evaluated in six groups of rat hearts (n = 6) following Langendorff perfusion and triphenyltetrazolium chloride staining. Controls underwent 30 min of global ischemia at 37 °C, followed by 10 min of simulated low- or high-quality CPR reperfusion and 90 min of reperfusion at 75 mmHg. The IH groups underwent IH at 34 °C during reperfusion. The U0126 group received U0126 (60 μM)-an extracellular signal-regulated kinase inhibitor-during reperfusion at 34 °C. The L-NIO (N-(1-iminoethyl)-L-ornithine dihydrochloride) group received L-NIO (2 μM)-an endothelial nitric oxide synthase inhibitor-5 min before global ischemia at 37 °C to the end of reperfusion at 34 °C. Infarct size did not significantly differ between the control and IH groups receiving low-quality CPR. However, IH with high-quality CPR reduced the infarct size from 47.2% ± 10.2% to 26.0% ± 9.4% (P = 0.005). U0126 reversed the IH-induced cardioprotection (45.9% ± 9.4%, P = 0.010), whereas L-NIO had no significant effect. Cardiopulmonary resuscitation quality affects IH-induced cardioprotection. Extracellular signal-regulated kinase may mediate IH-induced cardioprotection.
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