19MeV质子辐照小鼠损伤效应研究

Noci-influences of 19 MeV proton radiation on mice

目的探讨质子辐照对小鼠死亡率及主要器官损伤病理学改变的影响,为保证载人航天航天员的健康和生命安全提供参考。方法ICR小鼠,体重20～22 g,随机分为对照组和辐照剂量分别为4、8、16和32 Gy 4个辐照组。用氯胺酮(0．05 ml/只)麻醉,将小鼠用透明胶粘住鼠尾和后肢,两只并排,将背部固定于辐射范围内(7．5 cm^2)。采用中国原子能科学研究院的北京HI-13串列加速器加速的19 MeV质子,轰击1．3 mg/cm^2的Au靶,在大气环境下对小鼠进行均匀辐照。辐照后常规测定各组外周血网织红细胞的变化,同时观察小鼠死亡率。辐照第14天,动物再次称重后活杀,行解剖学和光镜检查。结果发现32 Gy质子照射组小鼠(n=4)在14 d内全部死亡,16 Gy质子照射组小鼠14 d内死亡1/5,4和8 Gy组小鼠30 d内全部存活。在照射小鼠背部7 d后出现损伤带,表现为随着剂量的增加,损伤带脱毛、皮肤灼伤程度加重。照射后小鼠外周血网织红细胞明显增多,脾小体明显缩小,骨髓出血、水肿、坏死,造血细胞减少,肺组织出血、水肿,细胞数量减少,皮肤变性、水肿,皮肤表皮和真皮纤维组织增生,表皮局部坏死脱落,毛囊和皮脂腺减少,睾丸曲细精管生精上皮细胞部分变性、坏死。结论本研究证实质子辐射对小鼠血液网织红细胞动态变化和死亡率及主要器官损伤病理学改变的影响明显,迫切需要深入研究。

Objective To investigate the fatality rate and the pathological changes of main organs induced by different dosages of 19 MeV proton radiation in mice so as to provide experimental data for the health protection of astronauts during space flight. Methods ICR mice, weighted 20～ 22 g, were randomly divided into control and 4 radiation groups which underwent proton radiation at the dosage of 4, 8, 16 and 32 Gy. respectively. The animals were anesthetized with ketamine （0.05 ml each）, and then fixed by sticking the tail and limbs with adhesive plaster, two mice in a row, and immobilized the back of animals within the radiated range （7.5 cm^2）. The mice were evenly radiated under atmosphericpressure with 19 MeV proton accelerated by Beijing HI-13 series-wound accelerator, bombarding at Au target of 1.3 mg/cm^2. Reticulocyte count in peripheral blood was examined 1, 3, 7 d after radiation exposure, and fatality rate of the animals was observed for 30 d. The mice were weighted and some of them killed on 14tb day after radiation for gross and microscopic examination. Results All the mice （n=4） died within 14 days in 32 Gy proton radiation group, and one out of five died in 16 Gy group. A Gy dose dependent damaged zone appeared on the back skin with hair loss and severe burn. Reticulocyte count in peripheral blood was increased significantly. Positive histological findings were as follows., degenerative changes of seminiferous tubules and fewer sperms in the lumen; obvious atrophied splenic malpigbian bodies; hemorrhage, edema, necrosis and fewer bematopoietic cells in section of bone marrow; edema, hemorrhage, less cellularity in section of lung tissue; epidermal and dermal fibrous hyperplasia, loss of some epidermal cells, decrease of hair follicles and sebaceous glands in section of skin underwent radiation. Conclusions This study indicates that proton radiation may induce the dynamic changes of blood reticulocyte count and pathological alterations of some organs, and higher radiation dosage may lead to high fatality rate of the mice. The mechanism of the damage needs to be further investigated.