Effects of nitrogen dioxide on pulmonary alveolar epithelial barrier properties

This study analyzed the effects of nitrogen dioxide (NO2) on alveolar epithelial permeability and transport properties. Primary cultured monolayers of rat type II pneumocytes, cultured on both nonporous and porous surfaces, were used as models of isolated alveolar epithelium for in vitro exposure to NO2. The effects of NO2 exposure for monolayers cultured on nonporous substrata were monitored by observing the changes in the total volume of fluid under the monolayer, using dome formation as a marker of net active solute transport. Alteration of the isolation and culturing conditions generated cultures with differing susceptibility to NO2. For bioelectric measurements and sodium flux studies, monolayers were cultured on tissue culture-treated Nuclepore filters and mounted in Ussing chambers. Spontaneous potential differences and short circuit currents were measured, and tissue resistances (Rt) were calculated. Monolayers exhibited Rt > 1200 Ω · cm2, consistent with the development of well-formed tight junctional complexes. Monolayers exposed to 2.5 ppm NO2 for 10-20 minutes demonstrated significant reductions in Rt and significant increases in 3H-glycerol and 14C-sucrose permeability, while short circuit current was only transiently affected