Abstract: Objective To study the antioxidation effects of L-carnitine against ischemia/reperfusion injury of rabbit cardiomyocytes in vivo and its possible mechanism.Methods Myocardial ischemia/reperfusion models were built in healthy New Zealand rabbits.Rabbits were subjected to 30 min myocardial ischemia followed by reperfusion for 1 h,3 h,5 h.Anesthetized rabbits were randomly divided into 3 groups:control group(n=5) in which left anterior descending coronary artery was exposed and a piece of silk thread was placed around the artery but not tied;MI/R group(n=15,then equally subgroup) in which normal saline was infused into sublingual vein after MI;L-carnitine group(n=15,then equally subgroup) received intravenous L-carnitine 3.0 g and saline 250 mL after MI.ECG monitoring throughout the experiment,free fatty acid(FFA),myocardial Ca⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase were all observed after reperfusion.The content of heat shock protein 70(HSP 70) obtained 5 mm below the ischemia/reperfusion region throughout the myocardial layer was determined with Western blot.Results MI/R caused significant changes in ECG and FFA compared with the control groups.The L-carnitine group showed protection against MI/R injury as evidenced by more effective improvement in ST of ECG,marked increase in Ca⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase and marked decrease in FFA(P<0.05).The content of HSP 70 was also dramatically increased.Conclusion L-carnitine can protect cardiomyocyte from ischemia/reperfusion injury;β-oxidation with free fatty acid improves energy metablism,stabilizes cell membrane probably by inducing HSP70 which will produce antioxidation function to protect myocardial cells.

Key words: myocardial ischemia/reperfusion, L-carnitine, HSP70, rabbit