title: Aquaporins in complex tissues. II. Subcellular distribution in respiratory and glandular tissues of rat.
abstract: The molecular pathways for fluid transport in pulmonary, oral, and nasal tissues are still unresolved. Here we use immunocytochemistry and immunoelectron microscopy to define the sites of expression of four aquaporins in the respiratory tract and glandular epithelia, where they reside in distinct, nonoverlapping sites. Aquaporin-1 (AQP1) is present in apical and basolateral membranes of bronchial, tracheal, and nasopharyngeal vascular endothelium and fibroblasts. AQP5 is localized to the apical plasma membrane of type I pneumocytes and the apical plasma membranes of secretory epithelium in upper airway and salivary glands. In contrast, AQP3 is present in basal cells of tracheal and nasopharyngeal epithelium and is abundant in basolateral membranes of surface epithelial cells of nasal conchus. AQP4 resides in basolateral membranes of columnar cells of bronchial, tracheal, and nasopharyngeal epithelium; in nasal conchus AQP4 is restricted to basolateral membranes of a subset of intra- and subepithelial glands. These sites of expression suggest that transalveolar water movement, modulation of airway surface liquid, air humidification, and generation of nasopharyngeal secretions involve a coordinated network of aquaporin water channels.
authors.affiliation: Department of Cell Biology, University of Aarhus, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Nielsen
authors.forename: L S
authors.initials: LS
authors.lastname: King
authors.forename: B M
authors.initials: BM
authors.lastname: Christensen
authors.forename: P
authors.initials: P
authors.lastname: Agre
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D051398:Aquaporin 1; D051400:Aquaporin 3; D051401:Aquaporin 4; D051402:Aquaporin 5; D020346:Aquaporins; D002462:Cell Membrane / Q000648:ultrastructure; D007150:Immunohistochemistry; D007473:Ion Channels / Q000032:analysis*; D008297:Male; D008565:Membrane Proteins; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D009092:Mucous Membrane / Q000166:cytology; D009297:Nasal Mucosa / Q000166:cytology; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D012137:Respiratory System / Q000166:cytology*; D012469:Salivary Glands / Q000166:cytology*; D013347:Subcellular Fractions / Q000648:ultrastructure
chemical_list: D000906:Antibodies; C496022:Aqp1 protein, rat; C496029:Aqp3 protein, rat; C496032:Aqp4 protein, rat; C496040:Aqp5 protein, rat; D051401:Aquaporin 4; D051402:Aquaporin 5; D020346:Aquaporins; D007473:Ion Channels; D008565:Membrane Proteins; D010446:Peptide Fragments; D051398:Aquaporin 1; D051400:Aquaporin 3