SCF-induced activation of Erk1/2 and p38 MAPK. CD34⁺ cells were cultured in EPO-containing medium for 6 days before the addition of SCF. (A) Cells were incubated with SCF (50 ng/mL) for the indicated times, and whole cell lysates (30 μg) were analyzed by immunoblot for phosphorylation of Erk1/2 and p38. The lowest panel shows the same blot stripped and reprobed with total p38 antibody to confirm that similar amounts of protein extracts were analyzed in each lane. (B) Cells were stimulated with SCF (50 ng/mL) for 10 minutes with and without preincubation with PD98059 (20 μM), SB202109 (5 μM), 2-ME (500 μM), or NAC (100 μM) for 30 minutes, and whole cell lysates were analyzed by immunoblot for phosphorylation of Erk1/2 and p38. The lowest panel shows the same blot stripped and reprobed with total Erk2 antibody to confirm that similar amounts of protein extracts were analyzed in each lane. Representative immunoblots from 3 independent experiments are shown.