|
|
|
|
|
|
|
||
Original Article |
verkman{at}itsa.ucsf.edu
The airway surface liquid (ASL) is the thin layer of fluid coating the luminal surface of airway epithelial cells at an air interface. Its composition and osmolality are thought to be important in normal airway physiology and in airway diseases such as asthma and cystic fibrosis. The determinants of ASL osmolality include epithelial cell solute and water transport properties, evaporative water loss, and the composition of secreted fluids. We developed a noninvasive approach to measure ASL osmolality using osmotically sensitive 400-nm-diam liposomes composed of phosphatidylcholine/cholesterol/polyethylene glycol-phosphatidylcholine (1:0.3:0.08 molar ratio). Calcein was encapsulated in the liposomes at self-quenching concentrations (30 mM) as a volume-sensitive marker, together with sulforhodamine 101 (2 mM) as a volume-insensitive reference. Liposome calcein/sulforhodamine 101 fluorescence ratios responded rapidly (<0.2 s) and stably to changes in solution osmolality. ASL osmolality was determined from calcein/sulforhodamine 101 fluorescence ratios after addition of microliter quantities of liposome suspensions to the ASL. In bovine airway epithelial cells cultured on porous supports at an air–liquid interface, ASL thickness (by confocal microscopy) was 22 µm and osmolality was 325 ± 12 mOsm. In anesthetized mice in which a transparent window was created in the trachea, ASL thickness was 55 µm and osmolality was 330 ± 36 mOsm. ASL osmolality was not affected by pharmacological inhibition of CFTR in airway cell cultures or by genetic deletion of CFTR in knockout mice. ASL osmolality could be increased substantially to >400 mOsm by exposure of the epithelium to dry air; the data were modeled mathematically using measured rates of osmosis and evaporative water loss. These results establish a ratio imaging method to map osmolality in biological compartments. ASL fluid is approximately isosmolar under normal physiological conditions, but can become hyperosmolar when exposed to dry air, which may induce cough and airway reactivity in some patients.
Key Words: water permeability • cystic fibrosis • fluorescence self-quenching • trachea • CFTR
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  W. Namkung, Y. Song, A. D. Mills, P. Padmawar, W. E. Finkbeiner, and A. S. Verkman In Situ Measurement of Airway Surface Liquid [K+] Using a Ratioable K+-sensitive Fluorescent Dye J. Biol. Chem., June 5, 2009; 284(23): 15916 - 15926. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. M. Effros Exhaled breath condensates and COPD Eur. Respir. J., May 1, 2009; 33(5): 1238 - 1238. [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Jing, J. A. Dowdy, M. R. Van Scott, and J. S. Fedan Hyperosmolarity-Induced Dilation and Epithelial Bioelectric Responses of Guinea Pig Trachea in Vitro: Role of Kinase Signaling J. Pharmacol. Exp. Ther., July 1, 2008; 326(1): 186 - 195. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Sivasankar and K. V. Fisher Vocal Fold Epithelial Response to Luminal Osmotic Perturbation J Speech Lang Hear Res, August 1, 2007; 50(4): 886 - 898. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. K. Sidhaye, A. D. Guler, K. S. Schweitzer, F. D'Alessio, M. J. Caterina, and L. S. King Transient receptor potential vanilloid 4 regulates aquaporin-5 abundance under hypotonic conditions PNAS, March 21, 2006; 103(12): 4747 - 4752. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. S. Launikonis and D. G. Stephenson Osmotic Properties of the Sealed Tubular System of Toad and Rat Skeletal Muscle J. Gen. Physiol., February 23, 2004; 123(3): 231 - 247. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. M. Effros, J. Biller, B. Foss, K. Hoagland, M. B. Dunning, D. Castillo, M. Bosbous, F. Sun, and R. Shaker A Simple Method for Estimating Respiratory Solute Dilution in Exhaled Breath Condensates Am. J. Respir. Crit. Care Med., December 15, 2003; 168(12): 1500 - 1505. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Song, J. Thiagarajah, and A.S. Verkman Sodium and Chloride Concentrations, pH, and Depth of Airway Surface Liquid in Distal Airways J. Gen. Physiol., October 27, 2003; 122(5): 511 - 519. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. L. Gibson, J. L. Burns, and B. W. Ramsey Pathophysiology and Management of Pulmonary Infections in Cystic Fibrosis Am. J. Respir. Crit. Care Med., October 15, 2003; 168(8): 918 - 951. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Jiang, Y. Song, C. Bai, B. H. Koller, M. A. Matthay, and A. S. Verkman Pleural surface fluorescence measurement of Na+ and Cl- transport across the air space-capillary barrier J Appl Physiol, January 1, 2003; 94(1): 343 - 352. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. S. Verkman, Y. Song, and J. R. Thiagarajah Role of airway surface liquid and submucosal glands in cystic fibrosis lung disease Am J Physiol Cell Physiol, January 1, 2003; 284(1): C2 - C15. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. D. Sonawane, J. R. Thiagarajah, and A. S. Verkman Chloride Concentration in Endosomes Measured Using a Ratioable Fluorescent Cl- Indicator. EVIDENCE FOR CHLORIDE ACCUMULATION DURING ACIDIFICATION J. Biol. Chem., February 8, 2002; 277(7): 5506 - 5513. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. A. Caldwell, B. R. Grubb, R. Tarran, R. C. Boucher, M. R. Knowles, and P. M. Barker In Vivo Airway Surface Liquid Cl- Analysis with Solid-State Electrodes J. Gen. Physiol., January 1, 2002; 119(1): 3 - 14. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. S. Verkman Lung disease in cystic fibrosis: is airway surface liquid composition abnormal? Am J Physiol Lung Cell Mol Physiol, August 1, 2001; 281(2): L306 - L308. [Full Text] [PDF]
|
|
|
|
|
|
Y. Song, S. Jayaraman, B. Yang, M. A. Matthay, and A.S. Verkman Role of Aquaporin Water Channels in Airway Fluid Transport, Humidification, and Surface Liquid Hydration J. Gen. Physiol., June 1, 2001; 117(6): 573 - 582. [Abstract] [Full Text] [PDF]
|
|
|
|
