we measured transepithelial impedance under three conditions : control conditions in which the epithelium was open-circuited and bathed on both sides with nacl-hco3 ringer 's solutions , amiloride conditions which were similar to control except that 100 microm amiloride was present in the mucosal bathing solution , and mucosal nacl-free conditions in which mucosal na and cl were replaced by potassium and sulfate or gluconate ( `` '' k+ ringer 's '' '' ) .
C0002502
amiloride
C0032821
potassium