Reappraisal of amiloride action on transepithelial electrical potential difference of isolated tracheal wall

The action of amiloride on two different components of airway electrical potential difference, one stable (PD) and the other transiently hyperpolarizable after gentle mechanical stimulation (dPD), was studied by means of isolated tracheal wall mounted in a modified Ussing apparatus. The immediate effect of amiloride, when added to the bathing and stimulating medium, was a partial depolarization, and a diminution or elimination of dPD. After at least 60 min incubation of the tracheal wall with amiloride in the presence of the drug in the bathing and stimulating fluid, both the PD, and dPD were no different from the control. This difference between the immediate and the sustained action of amiloride on airway PD suggests that there is an efficient regulatory system in the airway walls which stabilizes the transepithelial PD. The usefulness of amiloride as a drug for cystic fibrosis patients is discussed in the light of these findings.