Protective effect of melatonin on antioxidative system in experimental ischemia-reperfusion of rat small intestine.

AIMS: Effect of exogenously administered melatonin (N-acetyl 5-methoxytryptamine) on antioxidant systems in experimental Ischemia-Reperfusion (I-R) of rat gastrointestinal system (GIS) was examined. METHODS: A total of 40 rats were divided into 4 groups: Group 1 (Sham), Group 2 (I-R), Group 3 (I-R + 10 mg/kg melatonin) and Group 4 (I-R + 20 mg/kg melatonin). Activity levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were determined in small intestines. RESULTS: There was a significant (p<0.05) reduction in GSH-Px levels in Group 2 (64.16+/-7.02 U/mg protein) compared to Group 1 (80.15+/-9.32 U/mg protein). We observed a meaningful increase in GSH-Px levels in melatonin applied groups (Group 3: 75.94+/-9.83 U/mg protein, Group 4: 78.55+/-9.11 U/mg protein) compared to Group 2. Correspondingly, SOD activity levels were significantly reduced (p<0.001) in Group 2 (24.14+/-4.35 U/mg protein) compared to controls (52.91+/-6.13 U/mg protein). A stronger effect (p<0.001) of melatonin was observed on SOD levels compared to GSH-Px levels in both doses (Group 3: 38.96+/-6.39 U/mg protein, Group 4: 43.07+/-7.76 U/mg protein). Levels of selenium were reduced significantly in Group 2 (1.11+/-0.31 microg/g tissue) compared to Group 1 (2.01+/-0.19 microg/g tissue). Melatonin application in Group 3 (1.13+/-0.28 microg/g tissue) and Group 4 (1.89+/-0.48 microg/g tissue) caused an increase in selenium levels. There was a strong correlation between increases in selenium and GSH-Px levels in Group 4 (r:0.651 p<0.01). CONCLUSIONS: Melatonin seems to exert its antioxidant effect in GIS tract by stimulating SOD and GSH-Px. Selenium also seems to have an antioxidant contribution on protecting rat gastrointestinal tract I-R injury.

The role of melatonin in prevention of intestinal ischemia-reperfusion injury in rats.

BACKGROUND/PURPOSE: The aim of this study was to determine the effect of melatonin, a hormone that is known as an antioxidant, on the prevention of tissue damage during mesenteric ischemia/reperfusion (I/R). METHODS: A total of 40 young Wistar-albino rats were divided equally into 4 groups with varied treatment. Group 1 was control (sham), group 2 was I/R, group 3 was I/R plus melatonin (10 mg/kg) and group 4 was I/R plus melatonin (20 mg/kg). I/R was realized as follows: after laparatomy, a microvascular atraumatic clip was placed across the superior mesenteric artery (SMA) under general anaesthesia, and it was removed after ischemia for 30 minutes. The first dose of melatonin was applied intraperitoneally at the start of reperfusion. The second and third doses were applied intramuscularly on the first and second day. Only SMA dissection under general anaesthesia was carried out in the control group rats. On the third day of the study all the rats were killed, and their bowels were removed. Malondialdehyde (MDA) levels were assayed as an index of lipid peroxidation reflecting free radical reaction in the intestine. Histopathologic analysis was made using light microscopy in a blind fashion. RESULTS: The levels of tissue MDA were found to be significantly lower in groups 3 and 4 compared with group 2 (P < .05). The MDA levels of group 4 did not differ significantly from that of the control group (P > .05). The histopathologic results were consistent with the MDA levels. CONCLUSION: These results suggest that melatonin has a strong antioxidant effect in preventing intestinal I/R damage, and that this effect is exerted in a dose-dependent manner.