This suggests that the increase in mucus transport after saline solution inhalation is probably due to other factors such as changes in mucus properties or acute secretion of preformed mucus in response to the hyperosmolarity.
We chose concentrations of hyperosmolar solutions based on concentrations used in clinical stud-ies.” We recognize that immersion of a tracheal segment into a solution is different from inhaling the same hyperosmolar solution, as immersion allows equilibration between the intracellular and extracellular spaces; however, we have demonstrated that mucin secretion was stimulated only when the luminal side of the trachea was incubated with hyperosmolar solution. As well, kinetic studies confirm a very rapid onset of action and a short time to maximal stimulation, suggesting a direct stimulation that is independent of tissue osmotic equilibration. We speculate that the increased mucus output and mucus clearance in response to hyperosmolarity may be a protective response to prevent airway fluid loss. canadian health&care mall
With hyperosmolar challenge, mucin and ly-sozyme appear to be secreted together rather than independently, and we hypothesize that this is due to osmotic changes and therefore not specific for the secretion of mucous or serous secretions. The ratio of mucin to lysozyme secretion remained consistently at 2:1 in iso-osmolar (KHS) conditions as well as in 3% and 10% saline solutions. It is likely that serous secretions are important for flushing mucus from submucosal glands. In fact, this is one of the hypotheses regarding mucus gland obstruction in CF. The CF transmembrane regulator protein is most highly expressed in the serous cells of submucosal glands, and perhaps serous cell secretion is impaired in the CF airway, preventing effective secretion of mucins from submucosal glands.
Extrapolating these results to patients with airway disease should be done cautiously. The study reported here was performed in healthy ferrets, and the secretagogue effect could be different when there is airway disease. Nevertheless, the data presented in this article suggest that the therapeutic use of hyperosmolar aerosols may be of benefit when used for patients with impaired mucus clearance.