Introduction & Objective: Homocysteine is essential for protein metabolism. On the other hand, hyperhomocysteinemia is recognized as an independent risk factor for cardiovascular diseases, including oxidative stress damage, atherosclerosis, coronary artery disease and myocardial infarction. In spite of different study about the cardiovascular effect of homocysteine, the pathogenic mechanism of homocysteine effect on cardiovascular disease is not fully understood. With regard to this fact, the

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... fect of homocysteine on the isolated heart of rat has been considered in this study. Materials & Methods: Male Wistar rats (n=20) were used in this experimental study. The hearts of animals were isolated according Langendorff method and perfused with Kreb's solution. After 20 min stabilization period, hearts were perfused with Kreb's solution which contained different concentration of homocysteine in three groups (0.5, 0.1 & 0.05 mmol/lit) for 25 min. The different cardiac parameters were measured during different experimental periods and their changes were analyzed in each group with repeated measure ANOVA and were compared between groups with one way ANOVA and Tukey post test. Results: Results showed that the cardiac functional parameters including RPP (Rate Pressure Product) were not significantly affected by different concentration of homocysteine. On the other hand this amino acid resulted in increase of coronary flow. This increase started from 5 min after perfusion with homocysteine in three groups and continued to 25 min with 0.5 mmol/lit and to 10 min with 0.1 mmol/lit. Conclusion: In summary results showed the vasodilator effect of homocysteine on the coronary vessels without any changes in cardiac function.