Fig. 5. Effect of RA on cell proliferation and mitosis in MC3T3-E1 preosteoblasts on Ti surface. MC3T3-E1 cells on Ti discs incubated for 12 hours in a medium without serum were treated with or without 14 µg/ml RA. Total protein was extracted from these preosteoblasts and western blot analysis was performed. (A) Protein expression of Grab2, Ras and pERK1/2. β-actin was used as an internal control. (B-D) Quantitative analysis of western blots. RA: rosmarinic acid, Ti: titanium. *p<0.05, compared to control.