Na transport proteins are expressed by rat alveolar epithelial type I cells.
Despite a presumptive role for type I (AT1) cells in alveolar epithelial transport, specific Na transporters have not previously been localized to these cells. To evaluate expression of Na transporters in AT1 cells, double labeling immunofluorescence microscopy was utilized in whole lung and in cytocentrifuged preparations of partially purified alveolar epithelial cells (AEC). Expression of Na pump subunit isoforms and the alpha-subunit of the rat (r) epithelial Na channel (alpha-ENaC) was evaluated in isolated AT1 cells identified by their immunoreactivity with AT1 cell-specific antibody markers (VIIIB2 and/or anti-aquaporin-5) and lack of reactivity with antibodies specific for AT2 cells (anti-surfactant protein A) or leukocytes (anti-leukocyte common antigen). Expression of the Na pump alpha(1)-subunit in AEC was assessed in situ. Na pump subunit isoform and alpha-rENaC expression was also evaluated by RT-PCR in highly purified (approximately 95%) AT1 cell preparations. Labeling of isolated AT1 cells with anti-alpha(1) and anti-beta(1) Na pump subunit and anti-alpha-rENaC antibodies was detected, while reactivity with anti-alpha(2) Na pump subunit antibody was absent. AT1 cells in situ were reactive with anti-alpha(1) Na pump subunit antibody. Na pump alpha(1)- and beta(1)- (but not alpha(2)-) subunits and alpha-rENaC were detected in highly purified AT1 cells by RT-PCR. These data demonstrate that AT1 cells express Na pump and Na channel proteins, supporting a role for AT1 cells in active transalveolar epithelial Na transport.
Borok
Zea
Z
Will Rogers Institute Pulmonary Research Center, Division of Pulmonary and Critical Care Medicine, University of Southern California, 2020 Zonal Ave., Los Angeles, CA 90033, USA. zborok@usc.edu
Liebler
Janice M
JM
Lubman
Richard L
RL
Foster
Martha J
MJ
Zhou
Beiyun
B
Li
Xian
X
Zabski
Stephanie M
SM
Kim
Kwang-Jin
KJ
Crandall
Edward D
ED
D000818:Animals; D000911:Antibodies, Monoclonal; D004847:Epithelial Cells / Q000378:metabolism; D053503:Epithelial Sodium Channels; D015633:Extravascular Lung Water / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D015870:Gene Expression / Q000502:physiology; D008297:Male; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020545:Respiratory Mucosa / Q000166:cytology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D053503:Epithelial Sodium Channels; D015222:Sodium Channels; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase