"The aim of this study was to determine the effect of melatonin, a hormone that is known as an antioxidant, on functional responses of isolated ileal smooth muscle in rat intestinal ischemia-reperfusion. A total of 48 Sprague-Dawley rats were divided equally into 6 groups: Group 1 was control, Group 2 was sham-operated, Group 3 was ischemia, Group 4 was ischemia-reperfusion (IR), Group 5 was ischemia plus melatonin (IM) and Group 6 was ischemia-reperfusion plus melatonin (IRM). A dose of 10 mg kgG melatonin was 1 administered intraperitoneally. Thirty minutes of intestinal ischemia was followed by 90 min of reperfusion. Rats were sacrified after removal of ileal segments. Ileal segments were placed in isolated organ baths and relaxation responses for adrenaline were recorded. Additionally, Ileal segments were examined histopathologically and
biochemically. Comparisons of relaxation adrenaline responses of sham-operated group with ischemia group and IR group were found significant (respectively p<0.05, p<0.01). The comparison of IR group and IRM group
was found significant (p<0.05). The most extensive changes in morphology were detected in I/R group. In sections from this group, there were inflammation and necrosis in areas throughout the thickness of the
intestinal wall (Grade 3.5?0.189). The IRM group was histopathologically graded as 1.375?0.324. According to malondialdehyde values, I/R resulted in approximately 3 fold increase in MDA content of intestinal homogenates which is significantly different from that measured in control homogenates (p<0.01). Melatonin-treated groups were statistically indistinguishable from the control and sham-operated groups in terms of tissue MDA content (p>0.05). These results suggest that the 10 mg kgG of melatonin not only physiologically but 1 also biochemically and morphologically could be useful to normalize contractility injured by oxidative stress in intestinal ischemia-reperfusion."