Next the sections were incubated with the primary antibodies (1 : 10 dilution overnight for Fas, 1 : 50 dilution overnight for Bcl-2)

Next the sections were incubated with the primary antibodies (1 : 10 dilution overnight for Fas, 1 : 50 dilution overnight for Bcl-2). groups were compared. In the Group Acetaminophen C rats treated with melatonin, the cTn-T values were significantly lower than those in Groups B and D. In addition, malondialdehyde (MDA) and antioxidant enzymes including, superoxide Acetaminophen dismutase (SOD) and myeloperoxidase (MPO) were lower than those in Group B in the melatonin treated groups. The differences were statistically significant (p< 0.05). Histopathologic and immunohistopathologic studies also supported the effectiveness of melatonin. == Conclusion == Our study suggests that high dose melatonin, appears to offer protection against cardiac ischemia-reperfusion injuries in rats by scavenging Acetaminophen the free radicals and could have a potential clinical use in the management of myocardial ischemia. Keywords:Melatonin, myocardial ischemia-reperfusion, antioxidant, Fas and Bcl-2 expression == INTRODUCTION == Cell injury occurring after ischemia-reperfusion (I/R) in the heart is attributed to necrosis caused by calcium overload, acidosis, and oxidative stress.1After I/R, myocardial cells die by necrosis and/or apoptosis. Apoptosis is usually a process for disposing of injured or redundant cells through self-destruction. 2Free radicals and antioxidants play an important Acetaminophen role in cellular damage that can cause atherosclerosis and myocardial infarction. Both neutrophils and free radicals, such as superoxide anions, hydroxyl radicals and hydrogen peroxide, can cause oxidative damage to cell lipids, proteins, and nucleic acids.3 Melatonin (N-acetyl-5-methoxytryptamine) is secreted by the pineal gland, and has been confirmed to be potent scavenger of hydroxyl and peroxyl radicals.3,4Many researchers have considered the antioxidant role of melatonin and it is ability to trap cellular free radicals.5In addition, melatonin has also been shown to act as an immune system modulator.6Although there is a large amount of consistent data available that shows the potential protective effect of melatonin in cells, a consensus still exists that reactive oxygen species play an important role in the pathogenesis of cardiac reperfusion injury.7Several previous studies have examined melatonin and its effect on cell death following ischemia-reperfusion. What differentiates our study is the combination of histological parameters, immunohistopathologic studies and biochemical parameters that support the hypothesis that high-dose melatonin provides effective protection following I/R. == MATERIALS AND METHODS == This study was performed in the Hakan etinsaya Clinical and Experimental-Research Center at Erciyes University. The Ethics Committee approved this study. All animals involved received humane care in compliance with the European Convention on Animal Care. == Animals == Male Sprague-Dawley rats (n = 40) weighing 310 to 340 g (average 321 g) were used in this study. Nos3 The rats were anesthetized with ketamine hydrochloride (20 mg/kg), intraperitoneally (i.p.), and heparin (500 IU/kg, i.p) was also administered. A left thoracotomy was performed, and the pericardium was incised. The left coronary artery was surgically occluded through ligation with a suture (monoflamant polypropylene, size 6.0) and than followed with a coronary reperfusion through the release of the tie. == Rats were separated in to four groups == Group A (n = 10) was the control group and no procedures were carried out. Group B (n = 10) was subjected to cardiac ischemia (20 minutes) – reperfusion (20 minutes) without Acetaminophen any treatment. Group C (n = 10) was treated with melatonin (50 mg/kg i.p, Sigma, M-5250, St. Louis, MO, USA) 30 minutes before ischemia (20 minutes) – reperfusion (20 minutes). Group D (n = 10) uderwent left coronary artery occlusion (ischemia time of 20 minutes) and then melatonin (50 mg/kg i.p.) was administered just before reperfusion. Rats that developed ventricular fibrillation or cardiac arrest during I/R were excluded from the study, so only the 40 rats that did not have any complications were used. For biochemical testing blood samples were taken from all rats via the atrium using a 22 G intravenous cannula (Polyflon) after 20 minutes reperfusion. Heparinized blood obtained from the rats was centrifuged at 2,000 rpm for 15 minutes at 4. After separating the plasma, the samples were stored at -20 until analysis. Tissue samples were taken from the left ventricle and bathed in.