RESUMO
PURPOSE: The present study is aimed to investigate the magnitude and kinetics of DNA damage in peripheral blood leukocytes of mice exposed to whole body gamma irradiation (WBI; 3 Gy) and its correlation with aggressiveness of thymic lymphoma (TL). MATERIALS AND METHODS: DNA damage was monitored in peripheral blood cells of individual mice by comet assay at different intervals of post-irradiation, which were correlated with weight of TL in respective mice at 120th day. To further study genomic radiosensitivity in TL development, peripheral blood samples collected at the 15th and 90th day of post-irradiation from control and WBI animals were irradiated (0.5 Gy) ex vivo followed by assessment of DNA damage by comet assay. RESULTS: The maximum DNA damage (tail moment) was observed at 5 min after WBI, which decreased at longer period, and was minimum at the 7th day after WBI. However, residual damage was observed in comparison to control and it persisted up to 90 days of irradiation. Tail moment values observed at an early time (5 min) of post-irradiation was better correlated (correlation coefficient, r = 0.84) with weight of TL than at longer time period (60 days; r = 0.21). Our results showed that in ex vivo irradiated (0.5 Gy) peripheral blood, the magnitude of DNA damage was higher in samples obtained from WBI mice than sham-irradiated controls suggesting enhanced genomic radiosensitivity in WBI mice. Genomic susceptibility to radiation observed in peripheral blood from WBI animals showed better correlation with weight of TL at the 15th day (r = 0.9) post-irradiation period than at the 90th day (r = 0.44). CONCLUSION: These results suggest that the magnitude of radiation-induced initial DNA damage in peripheral blood leukocytes and genomic radiosensitivity could be an indicator of TL aggressiveness in mice.
