Establishment of Irradiation Induced Lung Injury in Rats Model and Related Mechanism Research

Objective: To establish and investigate rats model of radiation induced lung injury.Methods: Group-received irradiation on the thoraces with single fraction 22 gray γ rays from60Co,n=70.Randomly chosen 6 rats once were sacrificed at 1,7,15,21,30,60 and 120 days after irradiation.Body and whole lung weight of rats were measured to calculate lung coefficient.Right lung were extracted to observe the pathological changes and collagen fiber deposition of lung tissue by HE,Masson and Sirius red staining.Left lung were extracted to measure Hydroxyprolin content of lung tissue.Serum was extracted from venous blood to measure MDA content,T-SOD activity and TGF-β1 level.Eighty male SD rats were assigned randomly to control group-received sham-irradiation,n=10 and treatment.Results:(1) Macro changes such as depilation of thoracic and back where was irradiated,dermal,swelling and congestion of lung appeared in 15 days after irradiation and got worse later.Lung collapse and punctiform or trabs focus of fibrosis appeared in 60 to 120 days after irradiation.Compared with the control group,the pathomorphism change of model rats in early stage-7 to 30 days after irradiation represent small vessels anapetia,widened interalveolar septum,effusion in alveoli of lung and inflammatory cell infiltration.The pathological changes of model rats' lung in late stage-60 to 120 days after irradiation mainly represent cellular proliferation and collagen fiber deposition in lung parenchyma.(2) The total SOD activity in model rats serum increases transiently in 1 and 7 days after irradiation and the difference is significant compared with control group(P0.05),while the total SOD activity in model rats serum after 7 days maintained low level(vs control group P 0.05).The MDA content in model rats serum began to increase significantly in 1 day after irradiation(vs control group P=0.007) and the increase last to 120 days(vs control group P0.001).(3) The TGF-β1 content in model rats serum increased significantly in 15 days after irradiation(vs control group P0.05) and the increase last to the sequent times. Conclusion: A rats model of radiation induced lung injury was established successfully. Oxidative stress may play an important role in the progress of radiation induced lung injury.