Fig. 7.

UTP-stimulated ERK1/2 phosphorylation is epithelial growth factor (EGF) receptor and Src dependent. A: confluent ASMCs were serum starved for 24 h before challenge with UTP (100 μM) for the indicated time periods. ASMCs were lysed, and phospho-ERK1/2 immunoreactivity was determined by standard immunoblotting techniques (top panels). To verify equal gel loading, all blots were stripped and reprobed with anti-ERK1 antibody (bottom panels). A: representative immunoblots show the effects of UTP alone or in the presence of the EGF receptor inhibitor AG1478 (250 nM), Src inhibitor PP1 (5 μM), or both inhibitors (added 30 min before UTP). B: cumulative densitometric analysis of UTP-stimulated ERK1/2 phosphorylation: data are shown as means ± SE for 4 experiments in cells prepared from 4 different animals. Inclusion of AG1478 or PP1 significantly attenuated UTP-stimulated ERK1/2 phosphorylation (**P < 0.01; two-way ANOVA, Bonferroni's post hoc test).