Adaptive Response with Oxidative Stress from CT Scans and Exercise in Mice

We speculated that oxidative stress produced by repeated low dose diagnostic CT scans (10 mGy/scan, 2d/wk, 10 wk) would induce an adaptive response (AR) in C57BL/6 mice. We postulated that additional oxidative stress produced by exercise (1hr, 3d/wk, 10wk could further enhance the AR. We analyzed DNA double strand break (DSB) levels and genomic damage to stem cells via gH2AX foci and micronucleated reticulocytes (MN‐RET) flow cytometric assays, respectively. Following a challenge dose (1 Gy) in vitro, cells from CT mice had a significant increase (14%) in DNA DSBs compared to control and CT/exercised mice (p<0.035). A higher 2 Gy challenge dose showed that there was a significant reduction (16%) in DNA DSBs in CT/exercised mice (p = 0.002). When genomic damage was assessed, mice that had CT scans had significantly higher levels of MN‐RET (46% higher) compared to controls (p < 0.009). Interesting, the CT/exercise mice did not have any detectable increase in MN‐RET levels. After an in vivo 2 Gy challenge dose, control mice and CT mice had similar high levels of induced MN‐RET but there was a significant reduction (14%) in MN‐RET levels in the CT/exercise mice (p< 0.025). This research shows that CT scans can induce an AR in mice; however, this response is significantly modified by exercise. This research was supported by US DOE, Low Dose Research Program (DE‐FG02‐07ER64343) and NSERC.