Fig. 4. The effects of procaine on carbachol-induced protein tyrosine phosphorylation in PC12 cells. The cells were treated with the indicated concentrations of procaine (Pro) for 10 min and then stimulated in the presence (+) or the absence (−) of 1 mM carbachol for 2 min. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis and Western blot analysis with anti-phosphotyrosine antibody were performed. The carbachol-induced protein tyrosine phosphorylation of 44- and 42-kd proteins was inhibited by procaine in a dose-dependent manner. The molecular mass markers of p44 and p42, expressed in kilodaltons, are indicated on the left.