Cardioprotective activity of silymarin in ischemia-reperfusion-induced myocardial infarction in albino rats.
BACKGROUND
There is comprehensive experimental and clinical evidence that either exogenous supplementation of natural antioxidants or augmentation of endogenous antioxidants attenuates myocardial infarction.


OBJECTIVE
To investigate the effects of chronic administration of silymarin against ischemia-reperfusion-induced myocardial infarction in rats.


METHODS
Silymarin was administered orally to Wistar albino rats (200 g to 250 g) in three different doses (100 mg/kg, 250 mg/kg and 500 mg/kg), by gastric gavage for one week. At the end of this period, control (ischemia-reperfusion) groups and silymarin-treated groups were subjected to 30 min occlusion of the left anterior descending coronary artery and thereafter reperfused for 4 h.


RESULTS
Ischemia-reperfusion resulted in significant cardiac necrosis, indicated by elevated levels of serum marker enzymes such as serum glutamate oxaloacetate transaminase, serum glutamate pyruvate transaminase, lactate dehydrogenase, creatine kinase-isoenzyme and creatine kinase. A significant rise in the end products of myocardial lipid peroxides (malondialdehydes [MDAs]), loss of antioxidative enzymes (superoxide dismutase, catalase, glutathione S-transferase and reduced glutathione) and increased levels of myeloperoxidase in heart tissue were observed in the animals subjected to in vivo myocardial ischemia-reperfusion injury. Infarct size was measured by using the staining agent 2,3,5-triphenyltetrazolium chloride. A lead II electrocardiogram was monitored at various intervals throughout the experiment.


CONCLUSIONS
The present study showed that silymarin protected the endogenous antioxidant enzymes, suppressed the neutrophil infiltration during ischemia-reperfusion and limited the infarct size, with concomitant reduction in serum MDA, tissue MDA and serum marker enzymes in rats subjected to 30 min coronary artery occlusion followed by 4 h of reperfusion. Pretreatment with silymarin also protected rat hearts from a further drop in mean arterial blood pressure during reperfusion, and restored heart rate at the end of the reperfusion period.


CONCLUSIONS
The present study suggests that the phytochemical silymarin has cardioprotective activity against ischemia-reperfusion-induced myocardial infarction in rats.
Rao
Pragada Rajeswara
PR
Department of Pharmacology, University College of Pharmaceutical Sciences, Andhra University, Andhra Pradesh, India.
Viswanath
Routhu Kasi
RK