Mechanisms of Nitric Oxide (NO) Stimulation Cl‐ Secretion Across Airway and Lung Epithelial Cells.

We investigated the mechanisms by which NO modulate ion secretion across airway and alveolar epithelial cells. Addition of DETANONOate (1 to 1000 μM) into the apical compartments of Ussing chambers containing confluent monolayer of Calu‐3 cells, increases short circuit Cl‐ current (Isc) with an IC50 of 11.6±0.35 μM (X1 SEM; n=7). Addition of oxy‐myoglobin, CFTRinh‐172 as well as phosphatases into the apical compartments reversed this effect. In addition, pretreatment of Calu‐3 with the sGC inhibitor ODQ (10 M for 72 h) totally prevented the increase of Isc. DETANO increased Cl‐ secretion across basolaterally permeabilized Calu‐3 monolayers indicating that NO released from these agents upregulate CFTR function. Neither DATANONOate nor Br‐cGMP increased Cl‐ Isc across amiloride‐treated confluent monolayers of ATII cells. On the other hand, addition of forskolin, which stimulates cAMP, increased Isc by 3.00.3 n=6 which was inhibited by CFTRinh172. Similar levels of NO were measured in the apical compartments of Ussing chambers containing Calu‐3 or ATII cells using an ISO NO electrode. Western blotting studies revealed the presence of PKGI and PKGII in homogenates of Calu‐3 but not ATII cells. Similar levels of NO were detected in Ussing chambers containing either CAlu‐3 or ATII cells following addition of DETANO. Our results suggest that NO stimulated Cl‐ secretion on airway and not rat lung epithelial cells in vivo via activation PKGI and PKGII of cGMP.