Changes of WT-CFTR currents upon 8-N₃-ATP/ATP exchange. (A) Macroscopic currents immediately dropped to a steady state when the solutions were switched from 8-N₃-ATP to ATP. ATP was removed either 60 or 10 s after solution changes. (B) The subsequent current relaxations were compared. Red trace, 60-s exposure to ATP; black trace, 10-s exposure to ATP.