The influence of PP2 on L-arginine-induced tyrosine phosphorylation of the Na,K-ATPase α1 subunit. The samples were obtained from cells, cultured on permeable inserts, that had been pre-incubated with PP2 (10 μM) for 40 min before being exposed to L-arginine (3 mM) for 10 min in the continued presence of PP2. Part A shows a typical Western blot. Part B shows pY-10-Na,K-ATPase-α1 band density normalized to total Na,K-ATPase α1 (mean ± SEM) of three independent experiments. *P < 0.05 indicates a significant difference from control.