Therapy effect of cimetidine on spleen of mice irradiated with thoracic fractionated irradiation

Objective To investigate the protective effect of cimetidine on mice with fractionated X-ray irradiation through right thorax. Methods Thirty male C57BL/6 mice were randomly divided into control group, irradiation group and irradiation + cimetidine group (100 mg/kg), 10 mice in each group. Mice right thorax was locally irradiated with X-rays at a dose rate of 0.883 Gy/min to a cumulative dose of 24 Gy, 8 Gy per day in 3 d. After irradiation, the irradiation + cimetidine group was given cimetidine (100 mg·kg-1·d-1) for 7 d consecutively, and Ctrl and IR groups were given saline. Seven days after irradiation, the mice weight, spleen index and its T lymphocytes, B lymphocytes and NK cells were measured. Spleen tissue was stained with HE for pathological observation. Results The fractionated irradiation lightly suppressed mice growth but obviously induced abscopal damage on spleen so that the spleen index were decreased. The irradiation group (0.369±0.011) had statistically significant difference compared with the control group(0.396±0.022)(t=2.978, P<0.05), the spleen pathological structure became disorder, and the percentages of CD3+ , CD4+ , CD3+ CD4+ , CD3+ CD8+ lymphocytes in spleen were decreased significantly(t=5.754, 3.570, 4.442, 5.281, 4.570, P<0.05). Cimetidine could partially restore the weight of irradiated mice, relieved spleen structure damage and effectively restored lymphocyte subsets, and partly recovered the levels of CD3+ , CD3+ CD4+ , CD3+ CD8+ lymphocytes in the spleen (t=3.523, 2.706, 2.520, P<0.05). Conclusions Cimetidine, as a potential radiation protection drug, could effectively reduce the mouse spleen injury induced by X-ray fractionated irradiation by improving mouse immune function. Key words: Radiotherapy; Abscopal effect; Cimetidine; Spleen lymphocytes