Relative protein concentrations of branchial acid–base transporters. Branchial protein concentrations of acid–base transporters including Na+/K+-ATPase (NKA) (A), V-type H+-ATPase (VHA) (B), Na+/H+-exchanger 3 (NHE3) (C) and Rhesus protein (RhP) (D) determined after 20 h exposure to different pH conditions. Protein concentrations were normalized to ß-actin protein concentrations as an internal control. Letters indicate significant differences between pH treatments (p < 0.05). Bars represent mean ± SE (n = 3; with the average of 2 animals from each replicate).