Pulmonary epithelial permeability after inhaled distilled water 'fog'

The distinction between asthmatic and normal lung epithelium is that the changes induced by hypotonic solutions are associated in asthmatic patients with bronchoconstriction. It suggests that the trigger for bronchoconstriction is not at the epithelial surface, but either in the paracellular spaces or submucosa. Both these sites are likely to be exposed to the same changes in tonicity as the surfaces, if our observations on increased clearance of (99m)Tc DTPA do indeed reflect increased access to the paracellular spaces.