Radiation-induced incidence of thymic lymphoma in mice and its prevention by antioxidants.

Previous reports from our laboratory have shown that in Swiss female mice exposed to an acute dose (3 Gy) of whole body irradiation (WBI), induced thymic lymphoma (TL) resulted after three to four weeks of exposure. The present study was aimed to further evaluate dependency on gender and effect of age of mice at the time of irradiation on TL incidence. A significant decrease in body weight gain was observed in female mice exposed to WBI, which was found to be correlated with the increase in weight and size of thymus, compared to their respective controls. An increase in TL incidence was observed with the increased postirradiation time, which was 47, 80, and 93% after 90, 120, and 150 days of WBI, respectively, in female mice. In irradiated female mice, the TL incidence was significantly higher and the growth of tumor in terms of weight and size was more aggressive than in males of the same age. Moreover, mice with higher age groups at the time of irradiation showed substantial decrease in TL incidence and its aggressiveness; and these effects were more conspicuous in males than in females. In mice irradiated at the age group of three to four weeks, the TL incidence was 83 and 72% in female and male, respectively, which was decreased to 74% in female and 14% in male in the age group of 12-13 weeks. It was further observed that the postirradiation feeding of animals with antioxidants resulted in a significant decrease in TL incidence, and the prevention in TL incidence was more in animals fed with curcumin (55%) than with ascorbic acid and eugenol (20%). These results have provided significant new findings on the phenomenon of radiation-induced TL incidence related to gender and age at the time of irradiation and its prevention by postirradiation antioxidant feeding to mice.