Fig. 6. Localisation of epithelial calcium channel (ECaC), Na⁺K⁺-ATPase and nuclei in rainbow trout (Oncorhynchus mykiss) gill epithelia. The cell nuclei appear blue, ECaC appears green and Na⁺/K⁺-ATPase appears red; co-localization of ECaC with Na⁺/K⁺-ATPase appears yellow. (A) A representative image of a gill section treated with primary antibodies against ECaC and Na⁺/K⁺-ATPase. Areas within the boxes illustrate cells exhibiting only ECaC immunoreactivity; arrows indicate cells exhibiting only Na⁺/K⁺-ATPase immunoreactivity; asterisks indicate cells exhibiting co-localization of ECaC and Na⁺/K⁺-ATPase. (B) A representative image of a gill section pre-absorbed with the ECaC peptide antigen. (C) A representative image of a gill section on which the ECaC primary antibody was omitted. (D) A higher magnification image showing two Na⁺/K⁺-ATPase-positive cells with one displaying no ECaC immunoreactivity (1) and the other exhibiting co-localization (2). (F) A representative western blot showing the presence of a single immunoreactive band at 90 kDa in trout gill; the sizes of the protein markers (kDa) are indicated on the left.