Figure 4.

Influence of receptor autophosphorylation inhibition by tyrphostin AG1478 treatment. EGF induced MAPK activation in suspended and adhered hepatocytes. (A) Freshly isolated hepatocytes were stimulated by EGF in the absence (EGF) or presence of tyrphostin AG1478 (EGF + AG1478) and allowed to adhere and spread for 12 h. Bar, 80 μm. (B) Dose-dependent inhibition of EGFr and ERK1/2 phosphorylation after EGF stimulation (15 min) in the presence of increasing concentrations of tyrphostin AG1478 (0.25, 1, 10, and 50 μM) in 48-h-old cultured hepatocytes. For EGFr analysis, total lysates were analyzed with anti-phospho-tyrosine PY20 antibody. Zero corresponds to the control of solvent inhibitor (0.1% DMSO) added at the highest concentration used in the 50 μM AG 1478 treatment. The blot was reprobed with a mixture of ERK1 and ERK2 antibodies. These data are representative of three different experiments.