A concept of radiation hormesis: stimulation of antioxidant machinery in rats by low dose ionizing radiation.

OBJECTIVE

The concept of radiation hormesis has been the matter of discussion with regard to beneficial effects to biological systems from low doses of ionizing radiations. However, its molecular basis is not well understood till now and the present study is a step forward to elucidate how low levels of ionizing radiation prove beneficial for functioning of biological systems.

MATERIAL AND METHODS

Female Wistar rats weighing 100-120g were divided into four different groups. Each group consisted of eight animals. The animals in Group I served as normal controls for Group II animals which were subjected to whole body X-rays exposure of 20rads and were sacrificed 6 hours following exposure. Group III animals served as normal controls for group IV animals which were given whole body X-rays radiation of 20rads and were sacrificed 24 hours following exposure.

RESULTS

The levels of reduced glutathione (GSH), total glutathione (TG) were increased in liver, kidney, brain and blood after 6hrs as well as 24hrs following X-rays exposure. On the contrary, no significant change in the oxidized glutathione (GSSG) content was observed following X-rays irradiation in any of the organs. Further, the low dose of X-rays resulted in a significant decrease in the lipid peroxidation (LPO) in liver, kidney and brain, whereas it caused an increase in LPO levels in blood. The enzyme activities of catalase (CAT) as well as glutathione-S-transferase (GST) were also increased in different organs after X-rays exposure. Furthermore, low dose irradiation with X-rays caused a significant increase in the counts of total leukocytes, lymphocytes and eosinophils, whereas it decreased the counts of neutrophils as well as monocytes. Hence, our results clearly indicate that low dose X-rays radiation exposure stimulates endogenous antioxidant defense machinery and also causes an increase in whole blood lymphocytes and eosinophils responsible for providing key defenses.

CONCLUSION

Low doses of X-rays exposure may afford radiation hormesis by providing protection to organs from oxidative injury and support immune reaction.