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| Protective Effects of Melatonin on Damage of Lymphocytes in Mice Induced by Ionizing Radiation |
| ZHANG Xuan, WANG Zhenqi, LIU Yang, et al |
| MH Radiobiology Research Unit, School of Public Health, Changchun 130021, China |
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Abstract Objective To explore the protective effects of melatonin (MLT) on the damage of lymphocytes in mice induced by ionizing radiation and its mechanism.Methods The percentages of apoptotic bodies and the DNA lytic rates of thymocytes and splenocytes in mice in vitro and in vivo were detected with flow cytometry and fluorospectrophotometry, respectively.MLT was given to mice through intraperitoneal injection 60 min before the whole-body irradiation with 2 Gy X-rays.Twenty four hours after irradiation, the number of thymocytes and splenocytes, 3H-TdR incorporative rate (HTIR) of thymocytes and T and B lymphocyte transfo rming rates (TLTR and BLTR) induced by Con A and LPS were observed.Results The apoptosis of mouse thymocytes and splenocytes in vitro increased with significant dose-dependence in 0.5~6.0 Gy irradiation.When MLT of 2 mmol/L was added into thymocytes or splenocytes in vitro before irradiation with 0.5~6.0 Gy, the percentages of apoptotic bodies and the DNA lytic rates all decreased significantly as compared with those in the irradiation group.When MLT was injected into intraperitonium in mice 60 min befo re the whole-body irradiation with 2 Gy, the percentages of apoptotic bodies and the DNA lytic rates were significantly lower than those in the irradiation group, and near or lower than those in the sham-irradiation group.MLT of 0.1~2.5 mg/kg decreased the ly mphocyte apoptosis, but without significant dose-dependence.The number of thymocytes and splenocytes, HTIR, TLTR and BLTR were all significantly lower than those in sham-irradiation group 24 h after irradiation (P <0.001).When MLT of 0.5~10 mg/kg BW was given before irradiation, the number of thymocytes and splenocytes was significantly higher than that in 0 mg/kg BW group (simple irradiation, P <0.01), and the effect of MLT of 0.5 mg/kg BW was more obvious;HTIR of thymocytes also increased significantly, and effect of 0.5 mg/kg BW was more obvious;TLTR induced by Con A in 0.5 mg/kg BW group increased more significantly, while BLTR in 10 mg/kg BW group increased more significantly.Conclusion MLT can decrease the damage of ly mphocytes in mice induced by ionizing radiation in vitro and in vivo, and has the protective effect on immune functions.
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Received: 23 January 2005
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