Monobe Manami, Hino Makiko, Sumi Mariko, Uzawa Akiko, Hirayama Ryoichi, Ando Koichi, Kojima Shuji
Department of Radiation Biosciences, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Noda-shi, Chiba, Japan.
Int J Radiat Biol. 2005 Nov;81(11):855-60. doi: 10.1080/09553000600554804.
To examine the protective effects of melatonin on intestinal damage induced by gamma-rays.
Six-week-old Slc:ICR male mice were used. Mice were given whole-body irradiation at various exposure doses (7-21 Gy) with (137)Cs gamma-rays (0.98 Gy/min). The mice were orally administered 1 ml of either 1% carboxymethyl cellulose sodium salt (CMC) or melatonin (1, 5, 10 or 20 mg/ml) freshly prepared as a uniform suspension in CMC before or after irradiation. The concentrations of plasma melatonin were determined by the radioimmunoassay (RIA) method. The mice were killed at 3.5 days after the exposure. The jejunum was removed, fixed in formalin and then stained with hematoxylin and eosin. The numbers of crypts per transverse circumference were counted using a microscope for 10 histological sections of each mouse.
The intestinal damage caused by gamma-ray irradiation was prevented by melatonin correlating to dosage. The D(0) (slope of the dose-survival curve) value significantly (p < 0.05) increased from 1.55 +/- 0.19 (mean +/- SD) Gy to 1.98 +/- 0.16 Gy by orally administering 20 mg melatonin 30 min before irradiation. The radioprotective effect of melatonin continued for 6 h after the administration.
Melatonin is judged to be a potential protector against intestinal damage associated with radiotherapy. Further experimental and clinical studies on this subject are needed to allow its use for radiotherapy.
研究褪黑素对γ射线所致肠道损伤的保护作用。
选用6周龄的Slc:ICR雄性小鼠。小鼠接受不同剂量（7 - 21 Gy）的（137）Csγ射线全身照射（0.98 Gy/min）。在照射前或照射后，给小鼠口服1 ml以1%羧甲基纤维素钠盐（CMC）新鲜配制的均匀混悬液，其中分别含褪黑素（1、5、10或20 mg/ml）或CMC。采用放射免疫分析（RIA）法测定血浆褪黑素浓度。照射后3.5天处死小鼠。取出空肠，用福尔马林固定，然后进行苏木精-伊红染色。用显微镜对每只小鼠的10个组织学切片计数每个横切面的隐窝数量。
褪黑素对γ射线照射引起的肠道损伤具有剂量相关性保护作用。照射前30分钟口服20 mg褪黑素，D(0)（剂量-存活曲线斜率）值从1.55±0.19（均值±标准差）Gy显著（p < 0.05）增加至1.98±0.16 Gy。褪黑素的辐射防护作用在给药后持续6小时。
褪黑素被认为是一种潜在的预防放疗相关肠道损伤的保护剂。对此还需要进一步的实验和临床研究，以便将其应用于放疗。
