Patch clamp methods and reverse transcription-polymerase chain reaction (RT-PCR) were
used to characterize an apical K+ channel in Calu-3 cells, a widely used model of human
airway gland serous cells. In cell-attached and excised apical membrane patches, we found
an inwardly rectifying K+ channel (Kir). The permeability ratio was P Na/PK= 0.058. In 30
patches with both cystic fibrosis transmembrane conductance regulator and Kir present, we
observed 79 cystic fibrosis transmembrane conductance regulator and 58 Kir channels. The …