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A6370 - Oxidative Stress and Cell Death in Whole Body Low Dose X-Radiation Exposure in an In Vivo Model
Author Block: S. Puukila1, S. Muise2, J. McEvoy1, T. Bouchier1, A. M. Hooker1, D. R. Boreham3, D. Dixon1; 1Flinders University, Adelaide, Australia, 2McMaster University, Hamilton, ON, Canada, 3Northern Ontario School of Medicine, Sudbury, ON, Canada.
Rationale: Intensive care unit patients are frequently exposed to low dose diagnostic levels of radiation by computed tomography (CT) scans and X-radiation. A clear understanding of immunological and physiological effects is crucial for the responsible use of medical diagnostic procedures. We have previously shown that whole body exposure to low doses of radiation (2, 20 mGy) did not negatively affect lung mechanics/physiology or splenocyte proliferation in a Sprague Dawley rat model. However, exposure to higher doses (200 mGy, 4 Gy) led to decreased splenocyte proliferation. The aim of this study was to investigate if whole body X-radiation of rats results in oxidative stress and apoptosis in spleen or lung tissue. Methods: Male Sprague Dawley rats (200-250 g) were exposed to whole body X-ray at 0, 2, 20, 200 mGy or 4 Gy using an XRAD 320 irradiator. Outcomes were evaluated 0.5, 4, and 24 h post-irradiation. Middle right lung lobe and a portion of spleen were snap frozen and stored at -80°C. Oxidative stress markers were measured by Western blot. Another spleen portion was stored in optimal cutting temperature compound, sectioned at 5 µm and stained with TUNEL for apoptotic cell enumeration. A final portion was used to obtain splenocytes for cell smears after 48 hour culture with stimulant (concanavalin A or lipopolysaccharide). Cells differentials were calculated from DiffQuik stained smears. Immunofluorescences was used to identify T cell populations. Outcomes were analysed by two-way ANOVA with Bonferroni post-hoc. Results: Protein levels of oxidative stress markers increased in both spleen and lung tissue of animals exposed to higher doses (200 mGy, 4 Gy) of X-radiation when compared to sham. The number of apoptotic cells increased in spleens of rats 4 hours after exposure to a dose of 4 Gy when compared to sham, while spleens 30 minutes after 20 mGy exposure and 4 hours after 200 mGy exposure had significantly less apoptotic cells compared to sham. There was no significant difference in splenocyte macrophage or lymphocyte population after exposure. Furthermore, there was no significant difference in helper or cytotoxic T lymphocyte populations. Conclusion: Exposure to higher doses of X-radiation led to increased oxidative stress in lung and spleen and increased apoptosis in spleen of Sprague Dawley rats. Exposure to low doses did not appear to have any detrimental effects. Further establishment of this model is required for the full understanding on how diagnostic radiation exposure may affect patients in critical care.