Fig. 5. Detection of NHE2-expressing cells in rainbow trout gill by combined immunofluorescence and in situ hybridization. (A) PNA⁺ MRCs (labelled with arrows) were detected using a primary antibody against Na⁺/K⁺-ATPase (red) and biotinylated PNA (green). (B) In situ hybridization on the same section demonstrated that the PNA⁺ MRCs were enriched with NHE2 mRNA (labelled with arrows). Two PNA⁺ cells (labelled with asterisks) did not exhibit strong mRNA staining. No staining was observed when a sense probe was used (C) or when probe was omitted (D). Scale bar, 20 µm.