Whole-body X-irradiation Induces Acute and Transient Expression of Heme Oxygenase-1 in Rat Liver

Activation of the stress-inducible heme oxygenase-1 (HO-1) gene by X-irradiation was investigated in rat liver. When male Wistar MS strain rats (8 weeks) received whole-body irradiation of 17.0 Gy, 7 h later the activity of heme oxygenase in the liver was significantly enhanced (2.5 times). The level of HO-1 mRNA expression was increased by 2.3 and 4.0 times 2 and 4 h after radiation, and then declined at 7 and 10 h to the level of 2.0 and 1.6 times of the control. When the X-ray dose was varied from 4.0 to 21.7 Gy, the transcription of the gene was enhanced at all doses and the level of activation was dose-dependent. Finally, western blotting of irradiated liver demonstrated a significant increase in the level of HO-1 induced by X-rays, peaking at 4 h. Thus, X-rays were confirmed to be stressors that induce acute HO-1 expression transiently in the liver.