Phosphorylation state of intermediate molecules upstream of p38. FGF-2–induced phosphorylation of (A) MKK3/6, (B) MKK4, and (C) rac 1/cdc 42 was markedly inhibited in the presence of PDGF-BB (^*P < .001 vs FGF-2; ^**P < .05 vs FGF-2). PDGF-BB does not show any significant phosphorylating effect on these molecules, as expected according to data reported in Figure 1B. Bars indicate quantification of 3 experiments; one representative Western blot is shown below the bar graph in each panel.