Figure 7. Effects of NPPB, DPC and Cl⁻ removal on the ouabain-sensitive current in a hyposmotic solution.

The ouabain-sensitive current was measured in cells treated with 50 μM nystatin (apical application). NPPB (100 μM) almost completely abolished the ouabain-sensitive current. DPC (2 mM), which was applied to the apical and basolateral solutions, also significantly diminished the ouabain-sensitive current. Replacement of Cl⁻ with gluconate, which is a relatively impermeable anion, in the apical and basolateral solutions also significantly diminished the ouabain-sensitive current. Replacement of Cl⁻ with NO₃⁻, which generally has a permeability identical to Cl⁻, in the apical and basolateral solutions had no significant effects on the ouabain-sensitive current. n = 4-8.