UDCA treatment decreases ERK1/2 activity. HepG2 cells were either left untreated (control) or pretreated with 200 μmol/l UDCA (UDCA) or with 10 nmol/l metalloproteinase inhibitor TAPI-2 (TAPI) for 2 hours. Cells were then either stimulated with 10 nmol/l PMA (PMA) for an additional 24 hours or left non-stimulated. (A) Cell lysates from treated and control cells were analyzed by immunoblotting with anti-ERK1/2, and anti-phospho-ERK1/2 antibodies. Equal amounts of proteins were loaded in each lane; representative Western blots from three independent experiments are shown. (B) Signal intensities of phospho-ERK1/2 bands, which were densitometrically determined in three independent experiments (including the one shown), were normalized to ERK1/2 and compared to values obtained for control cells (100%). Mean values ± SEM are shown (n = 3). *p < 0.05.