大鼠半脑照射后早期脑内血流量和含水量变化的研究

Early changes in regional cerebral blood flow and water content in the rat brain after hemispheric irradiation

目的研究大脑受电离辐射后早期脑内血液循环的变化特点。方法对ＳＤ大鼠用４ＭｅＶ电子线１０，２０和３０Ｇｙ半脑照射后的３个月中，用氢清除法测量大脑不同区域的局部血流量，用干－湿重法测脑水份含量，并观察照射区皮肤、神经系统阳性体征与体重的变化。结果受照射后大鼠脑内各部位的血流量均有所下降，２０Ｇｙ与３０Ｇｙ照射后随时间的延长血流量下降的区域逐步扩大，尾壳核、额叶皮层和海马中血流量先后明显下降，３个月时整个半脑的区域血流量（ｒＣＢＦ）值降低，但１０Ｇｙ组的某些部位血流量值有所恢复。受照射后脑组织中存在脑水肿现象，其中以受照射后１个月时较为明显。３０Ｇｙ剂量组全部和２０Ｇｙ部分大鼠照射后射野内有脱毛，而且照射组大鼠在受照后１至３个月期间，体重的上升趋势低于未照射组大鼠。结论大鼠半脑１０～３０Ｇｙ照射后的３个月中有脑组织内局部血流量的减少和脑水肿的存在。

Objective To investigate the early changes in blood circulation in the rat brain after irradiation. Methods Three months after hemisphere irradiation of the Sprague_Dawley rats with single dose of 10,20 and 30Gy by 4MeV electron, we made measurement of the regional cerebral blood flow (rCBF) using hydrogen gas generated by electrolysis. Calculation of percentage brain water content with wet_dry weight formula and neurological signs were observed together with body weight.Results By comparison to the unirradiated hemisphere, the rCBF in the irradiated brain decreased in most of the rats. In the 20Gy and 30Gy groups, the area of blood flow decrease expanded with time, starting from the nucleus caudate putamen, to the frontal cortex and then the hippocampus. The rCBF of the whole irradiated hemisphere was reduced significantly three months after radiation. The water content of the irradiated hemisphere increased progressively which means brain edema existed in the meantime especially one month after radiation.Intra portal alopecia was observed in all rats which received 30Gy and most rats which received 20 Gy. The trend of body weight increase was less pronounced in 1～3 months in the irradiated rats than those unirradiated.Conclusions After hemisphere irradiation 10 to 30Gy,rCBF reduction and water content increase in the rat brain are observed for three months.