Abstract: Objective To observe the expression of survivin mRNA on thymus tissue apoptosis induced by ionizing radiation and study its role in radioactive thymus tissue apoptosis. Methods The mouse were irradiated with the X rays (1.75 Gy per time, 1 time per week for consecutive four times, total doses of 7 Gy).The mouse were killed and the thymus tissue were taken out at 30 and 60 d after they were irradiated(six mouse per time). The cell cycle and apoptosis rate were detected by flow cytometry. Survivin gene mRNA expression was detected by RT-PCR. Results The thymocytes and the of cells in G0/G1 and S phase in irradiation group were similar to that in control group, but the G2/M phase cells percentage was lower after irradiated 30 d and higher after 60 d compared with the control group (P<0.05).The thymocyte apoptosis in irradiation group was higher than that in control and the expression of survivin mRNA reduced significantly (P<0.05) at respectively time point. Conclusion Ionizing radiation can promote apoptosis in thymus by reducing survivin mRNA expressions.

Key words: Ionizing radiation, Thymus, Apoptosis, Survivin