EFFECT OF IONIZING RADIATION ON EXPRESSIONS OF p16、CyclinD1 and CDK4 IN MOUSE THYMOCYCTES

Using flow cytometry (FCM) , The changes in expressions of p16,CyclinD1 and CDK4 in the thymocytes of mice treated with different doses of whole-body irradiation or with a fixed dose and different post-irradiation intervals were analyzed. The results showed that the expression of p16 protein in mouse thymocytes began to increase significantly at 8h after 2Gy X irradiation, reached the peak level at 24h, kept a high level until 48h, and recovered at 72h. The CDK 4 protein expression decreased at 8h after 2Gy irradiation, reached the bottom level at 12h, and recovered at 48h. The expression of CyclinD1 protein showed a little reduction only after 2Gy irradiation . Overexpression of p16 depended on the doses of radiation (0.5-4Gy). The expression of p16 in 2Gy group was significantly increased in comparison with that in the sham-irradiated group ( p 0.01). The reduction of CDK4 expression was significant in 2Gy group ( p 0.01). CyclinD1 expression showed its decrease after 0.5-2Gy irradiation. These results suggested that p16/CyclinD1/CDK4/pRb pathway might play an important role in G 1 arrest of thymocytes induced by ionizing radiation.