The Effects of Melatonin Treatment on Oxidative Stress Induced by Ovariohysterectomy in Dogs

Abstract Background: As one of the most common surgeries performed in veterinary medicine, ovariohysterectomy (OHE) can induce stress in dogs. The antioxidant properties of melatonin have been confirmed in various studies. This study aimed to investigate the effects of melatonin administration on oxidative stress in dogs before and after OHE. In this study, 25 mature female intact dogs were selected and randomly divided into five equal groups: Melatonin, OHE, melatonin+OHE+melatonin, melatonin+anesthesia+melatonin, and control groups. Melatonin (0.3 mg/Kg/day, p.o.) was administrated to the dogs in the melatonin, melatonin+OHE+melatonin, and melatonin+anesthesia+melatonin groups on days -1, 1, 2, and 3 (day 0=OHE). Blood sampling was performed on days -1, 1, 3, and 5 of the study. Blood samples were immediately transferred to the laboratory and sera were separated and stored at -20 °C. Superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) concentrations were significantly higher in the melatonin and melatonin+anesthesia+melatonin groups compared to those of the control group. Results: The level of antioxidant enzymes significantly decreased in the OHE group compared to that of other groups. The administration of melatonin increased the level of antioxidant enzymes in ovariohysterectomized dogs. OHE significantly increased the concentration of malondialdehyde (MDA) in comparison to that of other groups. Melatonin administration significantly decreased the level of MDA in intact, anesthetized, and ovariohysterectomized dogs. Conclusions: It can be stated that the administration of melatonin one day before and during one week after OHE could control oxidative stress in dogs with increased antioxidant enzymes and decreased MDA levels.