Time course of Isc. A, control. Nystatin (50 μM, NYS) applied to the apical solution quickly increased Isc. Isc reached a steady state by 30 min after application of nystatin. Ouabain (1 mM, OUA) applied to the basolateral solution abolished most of the Isc. n = 10. B, amiloride applied to the apical solution. Although amiloride (10 μM, AMI) abolished the Isc, nystatin (NYS) increased the Isc similar to control. Ouabain (1 mM, OUA) applied to the basolateral solution abolished most of the Isc. n= 4. C, NPPB applied to the apical and basolateral solutions. NPPB (100 μM) abolished the Isc similar to amiloride. However, unlike amiloride, nystatin induced a small increase in Isc, and a small effect of ouabain was observed. n = 5.