5 PS ANION CHANNELS IN HUMAN AIRWAY EPITHELIAL-CELLS

Recent evidence from fluctuation analysis of whole-cell currents in human nasal epithelial cells suggests that most membrane current passes through anion-selective channels with a mean conductance of 4.5 pS. We used the excised single-channel patch clamp technique to examine small anion channels in the apical membranes of similar human nasal epithelial cells. Channels with conductances below 8.3 pS in symmetric 145 mM Cl- solutions were selected because this corresponds to the lower limit of the smallest anion channels observed previously in this tissue. The mean channel conductance observed was 5.57 pS with linear conductance and a mean open probability of approximately 0.2, increasing modestly with depolarization. Small channels were found in relatively high density with approximately one channel per patch. The conductance and density of these channels is therefore in good agreement with recent estimates based on current fluctuation analysis in these cells, indicating that small anion channels make a major contribution to total conductance in the airway epithelium.