This study aimed to investigate the radioprotective effect of melatonin (MLT) on brain damage in rats exposed to low and high dose rate radiotherapy. The dose rates of 10 MV photon beams used in the study were 600 MU/min and 2400 MU/min for low dose rate radiotherapy (LDR_RT) and high dose rate radiotherapy (HDR_RT), respectively. A total of 46 female Wistar albino rats aged between 8 and 12 weeks were divided in 6 groups. These groups were control, MLT, LDR_RT, HDR_RT, LDR_RT plus MLT and HDR_RT plus MLT, respectively. Rats in the radiation group received 16 Gy single dose whole body radiotherapy. Rats in the LDR_RT plus MLT and HDR_RT plus MLT groups received 10 mg/kg melatonin by intraperitoneal injection 15 min before radiotherapy. The rats were sacrificed 48 h after radiotherapy. Biochemical and histopathological methods analyzed radiation damage in rats. There was a statistically significant difference between the LDR_RT and HDR_RT radiation groups and the control group in terms of biochemical and histopathological parameters (p < 0.05). In the groups that received only LDR_RT and HDR_RT, the moderate neuro-degeneration scores were 1 and 4, respectively, while the moderate neuro-degeneration scores were 0 and 2 when MLT was applied to these groups. Superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) enzymes were decreased due to radiotherapy, whereas these enzymes were improved in MLT-treated groups. In conclusion, melatonin was found to be effective as a radioprotective agent in the prevention of brain damage caused by exposure to 10 MV photon radiation at dose rates of 600 MU/min and 2400 MU/min.

中文翻译：

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褪黑素对低剂量率和高剂量率放疗大鼠脑部放射生物学损伤的保护作用


本研究旨在探讨褪黑激素（MLT）对低剂量率和高剂量率放疗大鼠脑损伤的放射防护作用。研究中使用的10 MV光子束的剂量率对于低剂量率放疗（LDR_RT）和高剂量率放疗（HDR_RT）分别为600 MU/min和2400 MU/min。共有 46 只 8 至 12 周龄雌性 Wistar 白化大鼠分为 6 组。这些组分别是对照组、MLT、LDR_RT、HDR_RT、LDR_RT 加 MLT 和 HDR_RT 加 MLT。放射组大鼠接受16 Gy单剂量全身放射治疗。 LDR_RT加MLT组和HDR_RT加MLT组大鼠在放疗前15 min腹腔注射褪黑素10 mg/kg。放疗后48小时处死大鼠。生化和组织病理学方法分析了大鼠的辐射损伤。 LDR_RT和HDR_RT放射组与对照组在生化和组织病理学参数方面存在统计学显着差异（p < 0.05）。在仅接受 LDR_RT 和 HDR_RT 的组中，中度神经变性评分分别为 1 和 4，而当对这些组应用 MLT 时，中度神经变性评分为 0 和 2。超氧化物歧化酶 (SOD)、谷胱甘肽过氧化物酶 (GPx) 和过氧化氢酶 (CAT) 酶因放疗而减少，而这些酶在 MLT 治疗组中得到改善。总之，褪黑激素可作为放射防护剂有效预防因暴露于剂量率为 600 MU/min 和 2400 MU/min 的 10 MV 光子辐射而引起的脑损伤。