Genomic background helps determine sensitivity to TBI. Since the LD 50/30 (the dose that causes death in half of exposed mice within 30 days) following TBI varies between murine strains, we tested four murine strains to determine whether TBI sensitivity was associated with different levels of circulating DNA after radiation. The LD50/30 for the mice we tested - BALB/c, NIH Swiss, C3H/HeN, and C57BL/6 - is approximately 5.8 ± 0.3, 7.3 ± 0.2, 7.4 ± 0.3, and 8.5 ± 0.3 Gy, respectively. We estimated the radiation dose at which circulating DNA reached a peak level (peakGy), and mice were subjected to different doses at 1.84 Gy/min. The peakGy was 6, 7, 9, and 9 Gy for BALB/c, NIH Swiss, C3H/HeN, and C57BL/6, which corresponds to each strain's respective LD50/30. BALB/c, the most sensitive strain, had the lowest DNA concentration at peakGy, while C57BL/6, the most resistant strain, had the highest concentration at peakGy. At 7 Gy, the plasma DNA was approximately 3,754 ± 636, 8,238 ± 2,704, 9,773 ± 2,821, and 22,733 ± 5,914 ng/ml for BALB/c, NIH Swiss, C3H/HeN, and C57BL/6, respectively. These findings support our hypothesis that plasma DNA level is associated with genomic background. © 2012 Springer Science+Business Media, LLC.
