Melatonin prevents inflammation and oxidative stress caused by abdominopelvic and total body irradiation of rat small intestine

• Published in: Brazilian journal of medical and biological research Vol. 40; no. 10; pp. 1305 - 1314
• Main Authors: Guney, Y, Hicsonmez, A, Uluoglu, C, Guney, H Z, Ozel Turkcu, U, Take, G, Yucel, B, Caglar, G, Bilgihan, A, Erdogan, D, Nalca Andrieu, M, Kurtman, C, Zengil, H
• Format: Journal Article
• Language: English
• Published: Brazil Associação Brasileira de Divulgação Científica 01-10-2007
• Subjects: Animals; Antioxidants - therapeutic use; BIOLOGY; Circadian Rhythm; Inflammation - prevention & control; Intestine, Small - radiation effects; Irradiation; Male; MEDICINE, RESEARCH & EXPERIMENTAL; Melatonin; Melatonin - therapeutic use; Myeloperoxidase; Oxidative stress; Oxidative Stress - drug effects; Oxidative Stress - radiation effects; Radiation Injuries, Experimental; Radiation-Protective Agents - therapeutic use; Rats; Rats, Wistar; Thiobarbituric acid reactive substances; Thiobarbituric Acid Reactive Substances - metabolism; Thiobarbituric Acid Reactive Substances - radiation effects; Whole-Body Irradiation; Irradiation; Oxidative stress; Thiobarbituric acid reactive substances; Myeloperoxidase; Melatonin; Circadian rhythm
• ISSN: 0100-879X; 1414-431X; 1414-431X
• DOI: 10.1590/s0100-879x2006005000156

We investigated the day-night differences in intestinal oxidative-injury and the inflammatory response following total body (TB) or abdominopelvic (AP) irradiation, and the influence of melatonin administration on tissue injury induced by radiation. Rats (male Wistar, weighing 220-280 g) in the irradiated groups were exposed to a dose of 8 Gy to the TB or AP region in the morning (resting period - 1 h after light onset) or evening (activity span - 13 h after light onset). Vehicle or melatonin was administered immediately before, immediately after and 24 h after irradiation (10, 2.0 and 10 mg/kg, ip, respectively) to the irradiated rats. AP (P < 0.05) and TB (P < 0.05) irradiation applied in the morning caused a significant increase in thiobarbituric acid reactive substance (TBARS) levels. Melatonin treatment in the morning (P < 0.05) or evening (P < 0.05) decreased TBARS levels after TB irradiation. After AP irradiation, melatonin treatment only in the morning caused a significant decrease in TBARS levels (P < 0.05). Although we have confirmed the development of inflammation after radiotherapy by histological findings, neither AP nor TB irradiation caused any marked changes in myeloperoxidase activity in the morning or evening. Our results indicate that oxidative damage is more prominent in rats receiving TB and AP irradiation in the morning and melatonin appears to have beneficial effects on oxidative damage irrespective of the time of administration. Increased neutrophil accumulation indicates that melatonin administration exerts a protective effect on AP irradiation-induced tissue oxidative injury, especially in the morning.