The relatively nonselective potassium channel antagonist, tetraethylammonium ion (5 mM), shifted the concentration-relaxation curve for CF-AECal eightfold to the right, whereas glibenclamide, an ATP-sensitive potassium channel blocker, did not alter CF-AECal-induced bronchodilation. This evidence concerns the gene KCNA3 and cystic fibrosis.