Figure 2: Short-Circuit current ( ) in permeabilized MDCK cells: Na+-free media. A typical record is shown to demonstrate the experimental protocol. After equilibration in Na+-free medium, amphotericin B (10 μM) was added to the apical solution, to permeabilize the apical plasma membrane to small cations. This maneuver allows measuring basolateral pump currents. Then, Na+-free media was replaced by Na+-containing medium (50 mM) and the effects of ouabain (0.25 and 0.5 mM) was evaluated.