Contribution of concentration-sensitive sodium channels to the absorption of alveolar fluid in mice.
The concentration-sensitive sodium channel (Nac) is activated by an increase in the extracellular sodium concentration. Although the expression of Nac in alveolar type II epithelial cells (AEC II) has been reported previously, the physiological role of Nac in the lung has not been established. We characterized Nac expression and examined amiloride-insensitive sodium transport mediated by Nac in mouse lung. Immunofluorescence studies revealed that Nac did not colocalize with either aquaporin 5 or cystic fibrosis transmembrane conductance regulator, but partially colocalized with the epithelial sodium channel γ-subunit. Immunoelectron microscopy studies showed that Nac localized at the basolateral membrane of pulmonary microvascular endothelial cells (PMVECs). Nac mRNA and protein were expressed in PMVECs isolated from the lungs of mice. Image analysis indicated that sodium influx into the alveolar wall was dependent on increases in extracellular sodium concentration. We conclude that Nac expressed in PMVECs and AEC II contributes to the reabsorption of sodium via an amiloride-insensitive pathway during alveolar fluid clearance.
Department of Life Science, School of Science and Engineering, Kindai University, Higashi-Osaka, Osaka, Japan. Electronic address: hagi@life.kindai.ac.jp.
Teruki
T
Hagiwara
Department of Life Science, School of Science and Engineering, Kindai University, Higashi-Osaka, Osaka, Japan. Electronic address: physiology@life.kindai.ac.jp.
Shigeru
S
Yoshida
D062646:Acid Sensing Ion Channel Blockers / Q000494:pharmacology; D000327:Adsorption / Q000187:drug effects / Q000502:physiology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001826:Body Fluids / Q000187:drug effects / Q000378:metabolism*; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D008297:Male; D008813:Mice, Inbred ICR; D016253:Microscopy, Immunoelectron; D055806:Microvessels / Q000166:cytology / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000098:blood supply / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism*
D062646:Acid Sensing Ion Channel Blockers; D012333:RNA, Messenger; D015222:Sodium Channels; D000584:Amiloride; D012964:Sodium
Alveolar type II epithelial cell; Amiloride; Concentration-sensitive sodium channel; Pulmonary microvascular endothelial cell; Sodium transport