Introduction. Metabolism is the key factor underlying the cardiomyocyte function. The inadequate coronary perfusion results in tissue acidosis due to elevated lactate production, which is considered a sensitive marker of myocardial ischemia. Isoproterenol is a synthetic catecholamine that produces diffuse myocardial necrosis at high doses. The aim of the study was to assess the changes of serum and tissue lactate content in isoproterenol-induced acute myocardial infarction to evaluate the lactate potential as an early diagnosis marker of cardiac ischemia. Materials and methods. Forty adult male rats were divided into 5 groups: sham (L1=11), control 0.9% NaCl (L2=11), and with experimental myocardial infarction (L3=6, L4=6; L5=6), induced by the subcutaneous injection of Isoproterenol Hydrochloride solution 100 mg/kg, and sacrificed over 6 hours, 24 hours and 7 days post infarction. The results were presented by median and interquartile range. The groups were compared using Kruskal-Wallis and Mann-Whitney nonparametric tests, and the Spearman correlation coefficient was calculated (SPSS 23.0). A p≤0.05 was considered statistically significant. Results. Both glucose and lactate serum levels presented a slight decrease in L3, followed by a significant increase in L4, with a repeated fall in L5 group. In homogenate glucose content initially expressed an elevation in L3, with relevant decrease in L4, and inconsistent increase in L5, while lactate values significantly decreased in L3, returned to baseline levels in L4 and slightly declined in L5 compared to sham and control groups. Conclusion. The collected data suggest the utility of lactate assessment in early diagnosis and risk stratification in acute myocardial infarction.