Figure 1. Quantification of ouabain-sensitive I_SC.

Cells maintained under adult alveolar conditions (P_O2, 100 mmHg) were exposed to apical amiloride (10 μM) and nystatin (50 μM) as indicated. Nystatin evoked a slowly developing rise in I_SC and ouabain (1 mM) was added to the basolateral solution once this response had reached its peak value. The fall in I_SC evoked by this application of ouabain was measured in order to estimate the extrusion capacity of the basolateral Na⁺ pump.