Effect of Cl-, Na+, and amiloride on the electrical properties of dog tracheal epithelium, in vitro.

We investigated the effects on the cellular electrical properties of changes in the chemical gradient of Cl- and Na- across the luminal membrane of dog tracheal cells. We used standard microelectrode techniques to measure the electrical profile of these cells during Cl- and Na+ substitution in the luminal solution and during the addition of 10(-4) M amiloride, a Na+ conductance blocker, to the luminal solution. In 111 cell penetrations, we observed an apparent bimodal distribution of luminal membrane potential. About 75% of the cells constituted the lower mode, and the greatest number of penetrations in this mode had luminal potentials of -10 to -15 mV. The greatest number of penetrations in the higher mode had luminal potentials of -40 to -45 mV. In 16 penetrations, Cl- substitution changed the luminal membrane potential (+/- SE) by +12.3 +/- 0.6 mV and transepithelial potential by +11.6 +/- 0.9 mV. Both Na+ substitution and amiloride addition resulted in a minimal hyperpolarization of the luminal membrane potential with only a slight change in the submucosal potential. These results suggested the Cl- conductance contributed to a greater extent than that of Na+ to the maintenance of the luminal membrane potential difference and supported the model recently reviewed by Frizzell and coworkers (5) proposing Na+-dependent electrogenic CL- secretion in dog tracheal cells.