Objective To discuss formation mechanism of radiation fibrosis after introoperative radiotherapy in rabbits with tumor of pelvis .Methods 20 big female New Zealand albino rabbits were randomly allocated into control group , irra-diation of 4 weeks group , irradiation of 12 weeks group , and irradiation of 16 weeks group .Except control group , other groups all received irradiation .Pathological changes in rectum tissues were observed by light microscope .Proteins of rec-tum were extracted , and expressions of TGF-βor NF-κB were detected by Western blot .Results In rectum tissue sections of control group , cell arraged in order without inflammatory cell infiltrate .In irradiation of 4 weeks group , small amounts of inflammatory cell infiltrate , congesion and oedema were observed in sections .In irradiation of 12 weeks group , magnani-mous inflammatory cell infiltrate and significant congesion and oedema were observed in sections .Cells were necrosis , shedding , confused structure , and connective tissue in fibrosis .In irradiation of 16 weeks group , there were macrophage , inflammatory cell infiltrate and magnanimous fibrosis .With Azan staining, there was no fibrosis in control group , less blue fibrosis in irradiation of 4 weeks group, and magnanimous blue fibrosis in irradiation of 12 weeks group and irradiation of 16 weeks group .Proteins of TGF-βincreased with exposure time , and expression of NF-κB also increased with exposure time . Conclusion Irradiation could increase fibrosis and expression of TGF-βprotein,which might be related with the transcrip-tion of NF-κB.%目的：探讨盆腔肿瘤放疗后放射性纤维化形成的作用机制。方法将20只雌性新西兰大白兔随机分成照射4周组、照射12周组、照射16周组和空白对照组，除空白对照组外，其余各组新西兰大白兔均给予放射线照射。染色光镜下观察各组直肠组织的病理变化情况，提取直肠组织蛋白，采用蛋白印迹法检测TGF-β和NF-κB的表达。结果空白对照组直肠组织细胞排列整齐，无炎性细胞浸润；照射4周组可见少量炎性细胞浸润和充血水肿；照射12周组可见大量炎性细胞浸润、充血水肿明显，细胞肿胀坏死，脱落，黏膜组织结构紊乱，结缔组织呈纤维化改变；照射16周组可见巨噬细胞及中性粒细胞浸润和典型的外结缔组织纤维化改变。 Azan染色空白对照组直肠组织中未见纤维化表达，照射4周组直肠组织中少见蓝色纤维化表达，照射12、16周组直肠组织中可见大量纤维化表达。直肠组织中TGF-β、NF-κB蛋白表达均随照射时间延长而增加。结论放射性照射可增加直肠组织纤维化程度和TGF-β蛋白表达，其纤维化进程可能与促进NF-κB蛋白的核转录有关。
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