A, Serum starved cells were left untreated, or treated for 15 min with different concentrations with Ang II. Lysates were prepared and equal amount of proteins were run on a 8% SDS-polyacrylamide gel and immunoblotted with phosphospecific anti-caveolin-1 antibody cross-reactive to the 75 kDa protein. B, the blot in A was stripped and reprobed with anti-Stat3 antibody (loading control). C, shows that the EXP3174 pretreatment blocks Ang II-induced tyrosine phosphorylation of the 75 kDa protein. Cells were left untreated (control), or treated with Ang II for 15 min (10 nM), or first pre-treated with EXP3174 (1000 nM) for 15 min and then with Ang II (10 nM) for 15 min. Lysates were prepared, run on a 8% SDS-polyacrylamide gel, and immunoblotted with phosphospecific anti-caveolin-1 antibody. D, the blot in C was stripped and reprobed with anti-Stat3 antibody (loading control). These blots are representative of four independent experiments.