Transient permeabilization of airway epithelium by mucosal water. Widdicombe, J. H., F. Azizi, T. Kang, and J. F. Pittet. Children's Hospital Oakland Research Institute, 747 52nd Street, Oakland, CA 94609-1809 and Cardiovascular Research Institute and Departments of Anesthesia and Physiology, University of California, San Francisco, CA 94143
APStracts 3:0167A, 1996.
We describe a simple hypoosmotic shock procedure whereby the apical membrane of airway epithelium can be made transiently leaky to proteins and other macromolecules. Bovine or human tracheal epithelial cells were grown as confluent polarized cell sheets on porous inserts. While maintaining physiological saline on the basolateral surface, the mucosal surface was exposed to water. This led to marked increases in uptake of 14C-mannitol across both apical and basolateral membranes. On restoring saline to the mucosal surface, the 14C-mannitol permeability returned to preexposure levels with a t1/2 of 5 min. Mucosal water also increased efflux of lactate dehydrogenase (LDH) and the uptakes of fluorescent albumin and dextran (2000 kDa). Water-induced increases in mannitol permeability were similar at 4 and 37 C suggesting that pinocytosis was not the mechanism. Detailed time courses of the uptake of dextran and the loss of LDH and 36Cl showed that the bulk of the permeability increase occurred during the first 2-4 min exposure to water. Transepithelial resistance was reversibly decreased by exposure to water but short-circuit current responses to transport blockers and secretagogues remained qualitatively normal. The hypoosmotic shock procedure also successfully permeabilized apical membranes of primary cultures of nasal epithelial cells from a patient with cystic fibrosis (CF), and of JME/CF 15 cells, a cell line derived from CF bronchial epithelium. This simple and efficient procedure may prove useful in studies on the cell and molecular biology of airway and other epithelia. 

Received 18 August 1995; accepted in final form 1 February 1996.
APS Manuscript Number A911-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 April 96