Water movement across the airway epithelium is important for regulation of the volume and composition of airspace fluid. A novel approach is reported here to measure osmotic and diffusional water permeability in intact airways. Small airways (100-200 mu m diameter, 1-2 mm length) from guinea pig lung were microdissected and perfused in vitro using concentric glass holding and perfusion pipettes. For measurement of osmotic water permeability (P-f), the airway lumen was perfused with PBS (300 mOsM) containing a membrane impermeable fluorophore, fluorescein sulfonate (FS), and the airway was bathed in solutions of specified osmolalities, P-f determination was based on the change in FS fluorescence at the distal end of the airway resulting from transepithelial water transport, P-f was 4-5 X 10(-3) cm/s at 23 degrees C and independent of lumen flow rate (10-100 nl/min) and the magnitude and direction of the osmotic gradient (bath osmolality 50-600 mOsM). Temperature dependence measurements gave an activation energy of 4.4 kcal/mol (15-37 degrees C). P-f was not altered by 0.3 mM HgCl2 or 50 mu M forskolin, but was increased to 31 X 10(-3) cm/s by 100 mu g/ml amphotericin B, indicating that osmosis is not limited by unstirred layers. Diffusional water permeability (P-d) was measured by H2O/(DO)-O-2 (deuterium oxide) exchange using the H2O/D2O-sensitive fluorescent probe aminonapthelane trisulfonic acid in the lumen. Measured P-d was 3-6 X 10(-6) cm/s at 23 degrees C, indicating significant restriction to water diffusion by unstirred layers. Antibody localization of water channels showed strong expression of the mercurial-insensitive water channel (AQP-4) at the basolateral membrane of airway epithelial cells. These results provide functional evidence that water movement across the distal airway epithelium is mediated by water channels

Transepithelial water permeability in microperfused distal airways. Evidence for channel-mediated water transport

FRIGERI, Antonio;
1996-01-01

Abstract

Water movement across the airway epithelium is important for regulation of the volume and composition of airspace fluid. A novel approach is reported here to measure osmotic and diffusional water permeability in intact airways. Small airways (100-200 mu m diameter, 1-2 mm length) from guinea pig lung were microdissected and perfused in vitro using concentric glass holding and perfusion pipettes. For measurement of osmotic water permeability (P-f), the airway lumen was perfused with PBS (300 mOsM) containing a membrane impermeable fluorophore, fluorescein sulfonate (FS), and the airway was bathed in solutions of specified osmolalities, P-f determination was based on the change in FS fluorescence at the distal end of the airway resulting from transepithelial water transport, P-f was 4-5 X 10(-3) cm/s at 23 degrees C and independent of lumen flow rate (10-100 nl/min) and the magnitude and direction of the osmotic gradient (bath osmolality 50-600 mOsM). Temperature dependence measurements gave an activation energy of 4.4 kcal/mol (15-37 degrees C). P-f was not altered by 0.3 mM HgCl2 or 50 mu M forskolin, but was increased to 31 X 10(-3) cm/s by 100 mu g/ml amphotericin B, indicating that osmosis is not limited by unstirred layers. Diffusional water permeability (P-d) was measured by H2O/(DO)-O-2 (deuterium oxide) exchange using the H2O/D2O-sensitive fluorescent probe aminonapthelane trisulfonic acid in the lumen. Measured P-d was 3-6 X 10(-6) cm/s at 23 degrees C, indicating significant restriction to water diffusion by unstirred layers. Antibody localization of water channels showed strong expression of the mercurial-insensitive water channel (AQP-4) at the basolateral membrane of airway epithelial cells. These results provide functional evidence that water movement across the distal airway epithelium is mediated by water channels
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11586/42536
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 90
  • ???jsp.display-item.citation.isi??? 82
social impact