Figure 5: DBT induces Erk1/2 phosphorylation in cultured MG-63 cells. MG-63 cultures were serum starved for 3 h before the addition of DBT, RA, RAS, and RA + RAS extracts (1 mg mL−1) for different time. Total and phosphorylated inhibitor Erk1/2 and P-Erk1/2 were revealed by western blot analysis using specific antibodies. TPA at 0.1 μM served as a control. The lower panel shows the quantitation of phosphorylation from the blots by calibrating the densitometry. Values are expressed as the ratio to basal reading where time 0 equals to 1, and in mean ± SEM, where n = 4.