Abstract
We investigated that the effects of priming dose on the frequency of apoptosis and the expression of p53 in C57BL/6N mouse spleen. Mice received a whole body irradiation with 0.02Gy (667μGy/min, 0.8μGy/min) and 2Gy (0.91µGy/min) γ rays as follows; control: no treatment, group 1: 0.02Gy (667μGy/min), group 2: 0.02Gy (0.8μGy/min), group 3: 2Gy, group 4: 0.02Gy (667μGy/min) + 2Gy, group 5: 0.02Gy (0.8μGy/min) + 2Gy. The frequency of apoptosis and p53 expression were measured using TUNEL method and western blot. For the dose-rate effect study, the challenge dose was exposed when priming dose finished. There were no differences in the frequency of apoptosis among the control, group 1 and 2. The frequency of apoptosis in the group 3 and 4 significantly increased, and there was no difference between these groups. However, the frequency of apoptosis in the group 5 was approximately half of the group 3. For the time interval study, 0.02Gy (667μGy/min) was pre-irradiated. The frequencies of apoptosis were significantly lower in the primed mice at the time intervals of 2 to 168 h than those in the group 3. The expression of p53 in the group 2 increased compared that in the group 3. Furthermore, in group 4 and 5, the p53 expression increased compared to the group 3. In the group 5, the expression was maximum level. There were no expression of p53ser15 in the control, group 1 and 2. In group 3, its expression was high level, but low in group 4 and 5,We suggest that p53 stimulates repair system and then protects from apoptosis in the adaptive response.
