Fig. 3. Cellular distribution of phosphorylated ERK in primary hepatocytes (A), RTgill-W1 cells (B) and RTH-149 hepatoma cells (C) from rainbow trout stimulated by exposure to hypo-osmolarity (Hypo), EGF or Cu, in the absence or presence of leptomycin B (LB), as indicated. Cells were stained with an antibody against the dually phosphorylated form of ERK and a FITC-labelled secondary antibody and were then examined by confocal laser scanning microscopy. The right panel in the top row in A shows a negative control (Neg.) stained in the absence of the primary antibody. Scale bars, 20 µm (valid for all images in B and C).