Effect of osmolality on ion transport in Guinea pig airway epithelial cells

BACKGROUND: Increased osmolality of the airway surface fluid due to water loss associated with hyperventilation is considered to be a cause of exercise-induced asthma (EIA). AIM: We investigated the influence of changes in osmolality on airway epithelial ion transport in guinea pigs. METHODS: We explored from measuring open circuit potential difference in challenge with hypertonic saline or mannitol. RESULTS: Diphenylamine-2-carboxylate (DPC), amiloride, and disodium cromoglycate (DSCG) prevented an increase of the potential difference (PD) after exposure of tracheal mucosa to 0.9-10.8% hypertonic saline solutions (HSSs) (p < 0.05, p < 0.01, and p < 0.01, respectively on 1.8%). An increase of the PD was observed after a single dose of 1.8% hypertonic saline solution (HSS) was applied to the mucosa, but no increase was observed after a single exposure to a 585 mOsm/kg aqueous mannitol solution (585AMS). The results remained the same when a Cl-free solution was used as the perfusate. The change of airway epithelial cell thickness was only suppressed significantly by DPC (p < 0.01) after 1.8% HSS challenge. CONCLUSIONS: Not only the change of osmolality, but also changes of the Cl- and Na+ concentrations in airway surface fluid seem to have an important influence on the PD. cAMP-dependent Cl- channel may have a role, and the same mechanism may provoke EIA.