Effects of ozone on airway epithelial permeability and ion transport

Hartley guinea pigs had a 3-h sham exposure or a 3-h exposure to 1.0 ppm ozone. Within 2 h tracheas were excised and mounted in conventional Ussing chambers. Potential difference (PD), short circuit current (Isc), conductance (G) and unidirectional fluxes of 22Na, 36Cl and [14C]mannitol were measured in blinded experiments. Compared to the tracheal epithelia of sham-exposed animals, those from exposed animals had a larger PD (45%), an increased Isc (41%) and no change in G. In both groups, the Isc was approximately equivalent to net sodium absorption. The higher current in the exposed animal's tissues was disproportionately more sensitive to inhibition by the specific sodium channel blocker amiloride (44% vs. 13%). These observations suggest that early consequences of exposure of airway epithelium to ozone include increases in the density or open time of sodium channels in the luminal cell membrane or a change in sodium pump activity that increases the gradient for sodium entry across the luminal cell membrane. By 24 h after exposure these changes had been obscured by an increase in epithelial permeability, perhaps as the result of an inflammatory response to the ozone exposure.