Fig. 2. The effect of the Na⁺/H⁺-exchange inhibitor HOE-694 alone or in combination with propionate and phenamil on Na⁺ influx rates of trout gill cells. Gill epithelial cells were collected at a 1.03-1.09 g ml^-1 Percoll density interface layer, as described in the Materials and methods, and Na⁺ influx rates were conducted in low (15 mmol l^-1) Na⁺ saline to which 50 µmol l^-1 ouabain and 20 µmol l^-1 bumetanide were added (see Materials and methods). The open histogram represents the Na⁺ influx rate from control (pH 7.8) gill cells in the absence of HOE-694. The shaded (gray) histogram represents the Na⁺ influx rate from cells incubated in the presence of 50 µmol l^-1 HOE-694. The hatched histogram represents the Na⁺ influx rate for control gill cells in the presence of HOE-694 and 10 mmol l^-1 Na⁺ proprionate. The filled (black) histogram represents the Na⁺ influx rate for cells in the presence of HOE-694, proprionate and 10 µmol l^-1 phenamil. Data represent means + 1 S.E.M. (N=4). Means with different letters indicate that they are significantly different (P0.05).