RESUMO
OBJECTIVES: We aimed to investigate the effect of lipoic acid in the prevention of myocardial infarction in diabetic rats. METHODS: Rats were divided into five groups as control, ISO, LA+ISO, STZ+ISO and STZ+LA+ISO. To induce diabetes, single dose of streptozotocin was injected to STZ+ISO and STZ+LA+ISO groups. Lipoic acid (10 mg/kg/day) was injected for 14 days to LA+ISO and STZ+LA+ISO groups. To induce myocardial infarction, isoproterenol was injected to ISO, LA+ISO, STZ+ISO and STZ+LA+ISO groups on the days 13 and 14 of lipoic acid treatment. Cardiac necrosis and leucocyte infiltration were investigated histopathologically. Serum malondialdehyde levels, paraoxonase and lactonase activities were measured spectrophotometrically. RESULTS: Isoproterenol caused a significant increase in cardiac necrosis, leucocyte infiltration and serum lipid peroxidation whereas a significant decrease in serum paraoxonase and lactonase activities. In myocardial infarcted non-diabetic rats, while lipoic acid caused a significant decrease in cardiac necrosis, leucocyte infiltration and serum lipid peroxidation and a significant increase in serum paraoxonase and lactonase activities, it did not change these histopathologic or biochemical parameters in myocardial infarcted diabetic rats. CONCLUSION: Lipoic acid, at the dose of 10 mg/kg, is effective to prevent myocardial infarction in non-diabetic rats but it is insufficient in diabetic rats (Tab. 1, Fig. 2, Ref. 35).
