Objective: Nitric oxide (NO) and aquaporins (AQPs) are believed to play an important role in the pathogenesis of pulmonary inflammation and edema. The aim of this study was to investigate the role of NO synthase (NOS) and AQP in acute lung injury (ALI) lung following bleomycin inhalation in rats.
Design and setting: A prospective controlled trial in a university research laboratory.
Animals and interventions: Sprague-Dawley rats were treated by inhalation of 10 U/kg bleomycin hydrochloride in 5 ml of normal saline. Control rats were treated with 5 ml normal saline alone. The animals (6-8 rats per group) were killed on days 4, 7 or 14.
Measurements and results: We analyzed the change in expression of inducible NOS (iNOS), neuronal NOS (nNOS), endothelial NOS (eNOS), aquaporin 1 (AQP1) and aquaporin 5 (AQP5) over time by Western blot. Nitrate and nitrite concentrations were measured in bronchoalveolar lavage fluid (BALF) using a modified Griess reaction. The nitrite and nitrate concentrations in BALF from rats 4 days after bleomycin exposure were greater than those from saline-treated rats. Immunoblotting studies demonstrated increased levels of eNOS in the rat lung at 4, 7 and 14 days and iNOS at 7 and 14 days after bleomycin inhalation. However, nNOS expression was unaltered. Although AQP1 expression was decreased in rats at 4 days, AQP5 expression was increased at 4, 7 and 14 days.
Conclusions: This study demonstrates that NO metabolites increase along with eNOS and iNOS expression during the acute exudative phase in ALI, and that AQP and NOS are regulated independently in bleomycin-induced pulmonary edema.