Does small-dose gamma-ray radiation induce endogenous antioxidant potential in vivo?

The induction of in vivo antioxidant potential following small doses of gamma-ray irradiation was investigated in C57BL/6 mice. The antioxidant capacity of various organs was assessed in terms of the scavenging activity of cytosol fractions against 1,1-diphenyl-2-picrylhydrazyl (DPPH), a chemically stable radical. Significant elevations in the scavenging activity were recognized in several organs, including the liver, pancreas and brain, soon after post-irradiation with 50 cGy of gamma-ray. These increases persisted for 24 h. gamma-Radiation of the liver at 25-50 cGy elevated its cytosolic antioxidant capacity, but this was lowered at 200 cGy. In order to assess which antioxidants underlie this phenomenon, the content of a reduced form of glutathione (GSH) in liver was assayed as a function of time after gamma-irradiation at a dose of 50 cGy. The GSH content was significantly increased from 6 h after irradiation, and this change was consistent with that of the total radical scavenging potency of the liver against DPPH. Further, the elevation of GSH content was accompanied by elevated GSSG reductase activity induced by gamma-irradiation.