OCN, Cbfα1 protein expression of irradiated MC3T3-E1 cells. MC3T3-E1 cells were exposed to 0, 0.1, 0.5 and 1.0 Gy of X-irradiation respectively and cells were harvested on day 10 after irradiation. (A) The protein productions of OCN and Cbfα1 were detected by Western blot with β-actin as an endogenous control. (B) The quantitative date of OCN (B1) and Cbfα1 (B2) was band-density ratios compared to the control group. X-irradiation of 0.5 and 1 Gy resulted in obviously increase of protein level of OCN and Cbfα1 (*P < 0.05).