Gamma-irradiation induced the expression of HO-1 in p53+/+ but not in p53−/− mice. (A) Total RNA was extracted from thymus of p53+/+ and p53−/− mice either non-irradiated or whole body irradiated at a dose of 1 Gy. The thymus was taken 6 h post-irradiation. Hybridization to cDNA arrays of mouse stress/toxicology genes (AtlasTM filter arrays, Clontech, Palo Alto, CA, USA) was performed as described in Materials and Methods section. Signal intensity was normalized as described in Materials and Methods section. The normalized signal calculated for the thymus of irradiated mice was expressed relative to the thymus of non-irradiated mice. Results from microarray analysis (array) were confirmed by real-time quantitative RT-PCR as described in Materials and Methods section. The relative level of HO-1 mRNA measured by RT-PCR was normalized relative to GAPDH mRNA and the level of stimulation was calculated relative to non-irradiated animals. (B) HO-1 mRNA induction in thymus and spleen of mice at 3 h following whole body irradiation at a dose of 5 Gy. The level of HO-1 mRNA estimated by real-time quantitative RT-PCR was normalized as described below. The graphs represent the mean of four independent experiments with their respective standard deviation. NI, non-irradiated mice; IR, irradiated mice.
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