G1 Arrest and Relative Protein Expressions in Mouse Thymocytes Induced by Whole Body X—Ray Irradiation

Objective:To investigate the molecular regulation of G1 arrest of mouse thymocytes induced by ionizing radiation.Methods:Cell cycle was analyzed by flow cytomtry(FCM)following staining of cells with proidium iodide.Fluorescent staining and flow cytometry analysis were employed for measurement of protein expression.Results:it was demonstrated that G1 phase of mouse thymocytes increased significantly at 12h after whole body irradiation(WBI)with the doses of 0.5,1.0 and 2.0Gy,and at 24h following 2.0Gy exposure,measured by FCM.In the time course experiment,it was found that G1 phase of thymocytes increased significantly at 4h,reached a peak level at 24h and came down toward 48h after WBI with 2.0Gy X-rays.The results also showed that after 2.0Gy exposure,the expression of proteins in mouse thymocytes increased significantlty from 1h to 8h for p53,for p21 from 4h to 48h ,and for MDM2 at 4h and 8h.measured by FCM,But no change was found for GADD45 protein expression.Conclusion;These results suggest that G1 arrest could be induced by a single dose of 0.5Gy,1.0Gy or 2.0Gy,and its molecular control might be established through the p53-p21 pathway.