Long-term melatonin treatment reduces ovarian mass and enhances tissue antioxidant defenses during ovulation in the rat

• Published in: Brazilian journal of medical and biological research Vol. 44; no. 3; pp. 217 - 223
• Main Authors: Chuffa, L G A, Amorim, J P A, Teixeira, G R, Mendes, L O, Fioruci, B A, Pinheiro, P F F, Seiva, F R F, Novelli, E L B, Mello Júnior, W, Martinez, M, Martinez, F E
• Format: Journal Article
• Language: English; Portuguese
• Published: Brazil Associação Brasileira de Divulgação Científica 01.03.2011
• Subjects: Animals; Antioxidant defenses; Antioxidants - administration & dosage; Antioxidants - pharmacology; BIOLOGY; Catalase - drug effects; Catalase - metabolism; Female; Glutathione Peroxidase - drug effects; Glutathione Peroxidase - metabolism; Lipid peroxidation; Lipid Peroxidation - drug effects; MEDICINE, RESEARCH & EXPERIMENTAL; Melatonin; Melatonin - administration & dosage; Melatonin - pharmacology; Organ Size - drug effects; Ovary - anatomy & histology; Ovary - drug effects; Ovary - enzymology; Ovary mass; Ovulation - drug effects; Random Allocation; Rats; Rats, Wistar; Superoxide dismutase; Superoxide Dismutase - drug effects; Superoxide Dismutase - metabolism; Time Factors; Lipid peroxidation; Superoxide dismutase; Melatonin; Antioxidant defenses; Ovary mass
• ISSN: 0100-879X; 1414-431X; 1414-431X; 0100-879X
• DOI: 10.1590/s0100-879x2011007500018

Melatonin regulates the reproductive cycle, energy metabolism and may also act as a potential antioxidant indoleamine. The present study was undertaken to investigate whether long-term melatonin treatment can induce reproductive alterations and if it can protect ovarian tissue against lipid peroxidation during ovulation. Twenty-four adult female Wistar rats, 60 days old (± 250-260 g), were randomly divided into two equal groups. The control group received 0.3 mL 0.9% NaCl + 0.04 mL 95% ethanol as vehicle, and the melatonin-treated group received vehicle + melatonin (100 µg·100 g body weight(-1)·day(-1)) both intraperitoneally daily for 60 days. All animals were killed by decapitation during the morning estrus at 4:00 am. Body weight gain and body mass index were reduced by melatonin after 10 days of treatment (P < 0.05). Also, a marked loss of appetite was observed with a fall in food intake, energy intake (melatonin 51.41 ± 1.28 vs control 57.35 ± 1.34 kcal/day) and glucose levels (melatonin 80.3 ± 4.49 vs control 103.5 ± 5.47 mg/dL) towards the end of treatment. Melatonin itself and changes in energy balance promoted reductions in ovarian mass (20.2%) and estrous cycle remained extensive (26.7%), arresting at diestrus. Regarding the oxidative profile, lipid hydroperoxide levels decreased after melatonin treatment (6.9%) and total antioxidant substances were enhanced within the ovaries (23.9%). Additionally, melatonin increased superoxide dismutase (21.3%), catalase (23.6%) and glutathione-reductase (14.8%) activities and the reducing power (10.2% GSH/GSSG ratio). We suggest that melatonin alters ovarian mass and estrous cyclicity and protects the ovaries by increasing superoxide dismutase, catalase and glutathione-reductase activities.