Tracheal and bronchoalveolar permeability changes in rats inhaling oxidant atmospheres during rest or exercise

Abstract

Permeability of tracheal and bronchoalveolar airways of rats was measured and used to examine the effects of inhaled oxidant‐containing atmospheres. The atmospheres studied were (a) ozone (O ₃ ) at 0.6 ppm (1.2 mg/m³) or 0.8 ppm (1.6 mg/m ³ ); (b) nitrogen dioxide (NO ₂ )at 6 ppm (11.3 mg/m ³ ) or 12 ppm (22.6 mg/m ³ ); (c) O ₃ + NO ₂ at 0.6 ppm (1.2 mg/m ³ ) and 2.5 ppm (4.7 mg/m ³ ), respectively; and (d) a 7‐component particle and gas mixture (complex atmosphere) representing urban air pollution in a photochemical environment. The rats were exposed for 2 h. The effects of exercise during exposure were evaluated by exposing additional groups in an enclosed treadmill. Exposure of resting rats to 0.8 ppm O ₃ increased tracheal permeability to DTPA and bronchoalveolar permeability to diethylenetriamine pentaacetate (DTPA) and bovine serum albumin (BSA) at 1h after the exposure. Bronchoalveolar, but not tracheal, permeability remained elevated at 24 h after the exposure. Exercise during exposure to O ₃ increased permeability to both tracers in the tracheal and the brochoalveolar zones, and prolonged the duration of increased permeability in the tracheal zone from 1 h to 24 h, and in the bronchoalveolar zone from 24 h to 48 h. Permeability in the tracheal and brochoalveolar zones of rats exposed at rest to 6 or 12 ppm NO ₂ did not differ from controls. However, rats exposed during exercise to 12 ppm NO ₂ for 2 h developed a significant increase in tracheal and bronchoalveolar permeability to DTPA and BSA at 1 h, but not at 24 or 48 h, after exposure. Exposure at rest to 0.6 ppm O ₃ plus 2.5 ppm NO ₂ significantly increased bronchoalveolar permeability at 1 and 24 h after exposure, although exposure at rest to 0.6 ppm O ₃ alone increased bronchoalveolar permeability only at 1 h after exposure. Exposure to O ₃ + NO ₂ during exercise led to significantly greater permeability to DTPA than did exercising exposure to O ₃ alone. Resting rats exposed to a complex gas/aerosol atmosphere composed of the above O ₃ and NO ₂ concentrations, plus 5 ppm (13.1 mg/m ³ ) sulfur dioxide (SO ₂ ) and an aerosol of insoluble colloidal Fe ₂ O ₃ with an aerosol of manganese, ferric, and ammonium salts, demonstrated increased permeability at 1 and 24 h after exposure. Nitric acid vapor was formed in both the O ₃ + NO ₂ atmosphere and the complex gas/aerosol atmosphere. The particles in the latter also contained hydrogen ions equivalent in concentration to about 100 μg/m ³ of NH ₄ HSO ₄ suggesting that acidic components in the atmospheres produced effects that were additive upon the effect of O ₃ in producing both increase and prolongation of permeability in tracheal and bronchoalveolar zones of the respiratory tract.