Gamma-H2AX In Rat Lymphocytes After CT Scan:a Method For Prediction Of Radiation-Induced Rectal Injury

[Objective] Radiation proctitis cervical cancer is the most common complications of radiotherapy, there is no effective means of prediction. This study was designed to explore the correlation between gamma-H2AX foci number of peripheral blood lymphocytes after low dose radiation and acute radiation proctitis and its predictive value.[Methods] Two strains of rats (Wistar and SD),30rats of each group, were given whole body CT scan, the15mGy radiation, blood lymphocytes were obtained Oh,0.5h,2h,4h,12h,24h after the irradiation, Immunofluorescence was used to count nuclear gamma-H2AX foci of lymphocytes; the two strains of rats were irradiated at the pelvic area using a single20Gy exposure, rectal tissue and blood were separated0day,3days,1week,2weeks and4weeks after the irradiation; HE staining was used to observed histopathological changes; The microvessels of resected specimens were immunohistochemically stained with thrombomodulin(TM); ELISA was used to detect Serum Nitric oxide(NO) and Malondialdehyde(MDA) level. Pearson correlation method were used to analyse the correlation of gamma-H2AX and HE score, TM, NO and MDA.[Results]] The average foci number of Wistar rats is always higher than SD rats(P<0.05); The inflammatory score of Wistar rats was higher than SD rats2weeks and4weeks after pelvic irradiation(P<0.05); TM expression of rectal tissue of two strains of rats was significantly lower after irradiation(P<0.05), Wistar group was lower than SD group2weeks and4weeks after irradiation(P<0.05). NO and MDA levels were higher after irradiation(P <0.05), Wistar group was higer than SD group4weeks after irradiation(P<0.05). The number of gamma-H2AX foci is positively correlated with HE score, serum NO, MDA, negatively correlated with the level of TM.[Conclusion].Nuclear gamma-H2AX foci number in peripheral blood lymphocytes after low dose radiation like CT scan is positively correlated with the degree of inflammation and rectal acute radiation. Compared with traditional methods, immunofluorescence detect of gamma-H2AX foci is a sensitive, high specific and simple method, to accurately reflect the sensitivity to radiation of normal rectal tissue, with potential clinical value.