Figure 3: Determination of dose reduction factor for the GT3-PTX combination. Mice ( ) treated with one of the treatment groups (vehicle, 200 mg/kg of PTX, 200 mg/kg of GT3, and 200 mg/kg of GT3 plus 200 mg/kg of PTX) were exposed to a range of different radiation doses. The vehicle-injected and PTX-injected groups were irradiated at 7.5, 8.0, 8.5, 9.0, 9.5, and 10.0Gy TBI; GT3 group was irradiated at 9.5, 10.0, 10.5, 11.0, 11.5, and 12.0Gy TBI. GT3-PTX-injected groups were irradiated at 10.0, 10.5, 11.0, 11.5, 12.0, and 12.5 Gy TBI. Postirradiation survival was used to generate probit curve. Dose required for 50% mortality at 30 days (LD50/30) was calculated for each treatment group. Ratio of LD50/30-drug/LD50/30-vehicle, also known as dose reduction factor (DRF), was calculated as an index of radioprotective efficacy over a range of radiation doses with 95% confidence interval.