Comparison between the effects of L-Carnitine and Acetyl-L-Carnitine on myocardial infarction size in ischemic heart

Introduction: In the present study, potential differences between the effects of L-carnitine (LC) and acetyl-Lcarnitine (ALC) on ischemia/reperfusion (I/R)-induced myocardial infarction size were investigated. Methods: Male Wistar rats were randomly divided into five groups and then anesthetized by sodium pentobarbital. Hearts of the animals were removed and quickly mounted on a Langendorff apparatus and perfused under constant pressure by a modified Krebs-Henseleit (K/H) solution. The hearts were perfused during 30 min regional ischemia followed by 120 min reperfusion by normal K/H solution (as control) or enriched solution with 1.5 and 3 mM LC (groups 2 and 3) or ALC (groups 4 and 5). At the end of the reperfusion cycle, 0.25 % evans blue solution was infused to stain the non-ischemic area, then the hearts were cut into slices and incubated by triphenyltetrazolium chloride solution and fixed by formalin. The infarction size was determined by using a computerized planimetry package. Results: The infarct size after perfusion of isolated hearts with 1.5 (26±4.5%) and 3 mM LC (20±4 %) showed a significant reduction compared to the control value (45.6±3.4 %, P<0.01 and P<0.001, respectively). The same concentrations of ALC significantly lowered myocardial infarction size to 23.8±4 % (P<0.01) and 15.8±2.9 % (P<0.001), respectively. When the effects of similar concentrations of LC and ALC on the infarction size were compared, there was no statistically significant difference (p>0.05). Among the potential protective mechanisms of the agents, increase of glucose oxidation, reduction of lactate production, toxic fatty acid metabolites and removing free radicals from the myocytes seem to be more relevant. Conclusion: The results of this study demonstrated the protective effects of LC and ALC against I/R injuries by reduction of infarct size in isolated rat hearts without any important difference between the agents.