UDCA interferes with ADAM17 maturation. 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-ADAM17 antibodies. Equal amounts of proteins were loaded in each lane; representative Western blots from three independent experiments are shown. (B) Signal intensities of mature ADAM17 bands (85 kDa), which were densitometrically determined in three independent experiments (including the one shown), were normalized to immature ADAM17 form (130 kDa). Mean values ± SEM are shown (n = 3). *p < 0.05; **p < 0.01. (C) mRNA was isolated from HepG2 cells as described in the text. The relative expression levels of ADAM17 were followed by qRT-PCR. Expression was normalized to GAPDH and expressed as fold change of control sample. Mean values ± SEM are shown (n = 3). *p < 0.05.