Fig. 11. Immunocytochemical localisation of epithelial calcium channel (ECaC) and Na⁺/K⁺-ATPase in double-seeded rainbow trout gill epithelial cell cultures using (A) confocal or (B–D) epifluorescence microscopy. In B–D, the cell nuclei appear blue, ECaC appears green and Na⁺/K⁺-ATPase appears red; co-localization of ECaC with Na⁺/K⁺-ATPase appears yellow. (D) MitoTracker^TM was used to localize mitochondria-rich cells (stained green) and ECaC (red). A is a reconstruction of 22 optical sections showing the presence of ECaC-positive mitochondria rich cells (MRCs, arrows) lying on top of a confluent layer of ECaC-positive and ECaC-negative (asterisks) pavement cells. In B and C the cell types are: (1) ECaC-positive cells; (2) Na⁺/K⁺-ATPase-positive cells; (3) cells co-expressing ECaC and Na⁺/K⁺-ATPase; (4) cells positive for neither ECaC nor Na⁺/K⁺-ATPase. In D, the cell types are: (2) MRCs; (3) MRCs co-expressing ECaC.