Adult alveolar type II cells lack cAMP and Ca(2+)-activated Cl-channels.
We investigated the presence of Ca(2+)-activated Cl-channels in adult rat alveolar type II (ATII) using patch-clamp techniques. Only one active channel each, with a single channel conductance of 50 pS and an opening probability (Po) of 0.76 was found among 130 successful cell-attached and 5 inside-out patches. Addition of CPT-cAMP into the bath (500 microM) induced one active patch from 33 silent cell-attached patches. Incubation of 9 ATII cells, with ionomycin (1 microM), failed to elicit chloride single currents in 9 cell-attached patches. Cl- currents were also absent from 35 whole cell patches, even after the addition of 10 microM terbutaline in the bath or 1 mM ATP and 5 mM MgCl2 in the pipette. These results indicate that only a very small fraction of adult rat ATII cells express CFTR and suggest that Cl- ions are passively transported across the cell junctions.
Zhu
S
S
Department of Anesthesiology, University of Alabama at Birmingham 35233, USA.
Yue
G
G
Shoemaker
R L
RL
Matalon
S
S
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D018118:Chloride Channels / Q000096:biosynthesis* / Q000187:drug effects; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000032:analysis* / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000096:biosynthesis* / Q000187:drug effects; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013726:Terbutaline / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
D018118:Chloride Channels; D013873:Thionucleotides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D015759:Ionomycin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D008274:Magnesium; D013726:Terbutaline; D002118:Calcium