HNF4α and CK19 immunohistochemistry. Liver sections obtained from normal control rats (NRL, normal rat liver) (A and D), rats that underwent DAPM + BDL treatment (B and E), or repeated DAPM treatment (DAPM × 3) (C and F). B, E and C, F are serial sections. Brown nuclear staining indicated HNF4α positive cells in the left panel. Brown cytoplasmic staining in the right panel indicates CK19 positive cells. NRL bile ducts are HNF4α- negative and CK19 positive. However, after DAPM + BDL and DAPM × 3 treatment bile ducts turn HNF4α positive along with CK19. In addition, periportal hepatocytes also turn positive for CK19 after BDL + DAPM and DAPM × 3 treatment. PV, portal vein; BD, bile duct. Scale bar = 100 μm.