The objective of this study was to understand the effect of chronic low-dose radiation that induces in vivo radio-adaptive response. The animals were exposed chronically to natural radioactive materials (NORM) for one and two months which correspond to 10 &20 mSv which are comparable to the reality of areas with high background natural radiation (HBNR). Radioactivity assessment of samples was done using a high purity germanium -ray spectrometer. We conduct the study to understand the radio-adaptive response by exposure the experimental animals to challenge dose 2 Gy after continuous exposure to 10 & 20 mSv. Comet assay was performed in addition to some of antioxidant enzymes concentrations (superoxide dismutase (SOD), catalyze enzyme (CAT), reduced and oxidized glutathione (GSH).
Chronic exposure to 10 and 20 mSv showed DNA damage as a high elevation in comet assay, parameters. Also the results of the present work showed a low production of antioxidant enzymes CAT, SOD & GSH in both chronic exposure (10 & 20 mSv and challange dose 2 Gy). The exposure to 20 mSv before 2Gy gamma rays resulted in an enhancement of antioxidant enzymes accompanied with decreasing in free radical which is represents as an adaptive response. . It can be said that for low radiation doses, which are less than 100 mSv, their effects differ from high doses, so that it can be said that the body has an adaptive response and the application of the linear non-threshold model must be reviewed for these doses.