正常大白鼠经伽玛刀照射后脑组织胶质纤维酸性蛋白的变化

目的：用伽玛刀照射正常鼠脑组织后，研究不同时间脑组织中胶质纤维酸性蛋白（GFAP）及脑组织水含量变化，了解伽玛刀照射后脑组织损伤的变化过程。方法：用伽玛刀将160Gy的剂量照射正常SD鼠脑组织，分别于照射后第1d，第7d，第14d，第28d断头取脑，免疫组化方法检测脑组织中GFAP水平，微比重法测定脑组织比重，江镜下观察受照射侧脑组织病理改变。结果：（1）免疫组化检测：照射后第1d，靶区GFAP阳性星形细胞开始增多，随着时间的延长，GFAP染色加深，胶质细胞增生明显，第28d，靶区中央区出现直径约4mm的坏死灶，坏死区周边可见明显增多的GFAP阳性星形细胞（P＜0．01）。（2）光镜观察：照射后第1d可见脑实质内细胞肿胀，第7d红细胞从血管漏出，血管外间隙增宽，第14d靶区伊文氏兰漏出。（3）照射后14d可见照射侧脑组织比重明显减轻。结论：GFAP可作为衡量脑放射性损伤的指标。同时，在照射后早期即出现脑水肿反应和血脑屏障破坏。

Alterations of glial fibrillary acidic protein in rat brain after gamma knife irradiation]

OBJECTIVE: To study glial fibrillary acidic protein (GFAP) immunoreactivity in different time and water content of the rat brain treated with gamma knife radiotherapy and to understand the alteration course of the brain lesion after a single high dose radiosurgical treatment. METHODS: In the brains of the normal rats were irradiated by gamma knife with 160 Gy-high dose. The irradiated rats were then killed on the 1st day, 7th day, 14th day, and 28th day after radiotherapy, respectively. The positive cells of GFAP in brain tissue were detected by immunostaining; the water content of the brain tissue was measured by microgravimetry. The histological study of the irradiated brain tissue was performed with H.E. and examined under light microscope. RESULTS: The numbers of GFAP-positive astrocytes began to increase on the 1st day after gamma knife irradiation. It was enlarged markedly in the number and size of GFAP-stained astrocytes over the irradiated areas. Up to the 28th day, circumscribed necrosis foci (4 mm in diameter) was seen in the central area of the target. In the brain tissue around the necrosis, GFAP-positive astrocytes significantly increased (P < 0.01, compared with the control group). The swelling of cells in irradiated region was observed on the 1st day; after irradiation endothelial cells degenerated and red blood cells escaped from blood vessel on the 7th day; leakage of Evans blue dye was observed in the target region on the 14th day. There was a significant decrease of specific gravity in the irradiated brain tissue the 14th and 28th day after irradiation. CONCLUSION: The results suggest that GFAP can be used as a marker for the radiation-induced brain injury. The brain edema and disruption of brain-blood barrier can be occurred during the acute stage after irradiation.