Early Response of the Canine Respiratory Tract Following Long-Term Exposure to a Sulfur(IV) Aerosol at low Concentration. II. Biochemistry and Cell Biology of Lung Lavage Fluid

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Abstract
Eight beagle dogs were exposed for 290 d to a low concentration of sulfur(IV/) aerosol 10.3 mg m−3 S(IV) corresponding to 0.6 mg m−3 sulfur dioxidel. No clinical symptoms were found that could be correlated with the pollutant. However, significant changes were observed in some of the biochemical and cellular parameters determined in sequential bronchoalveolar lavage (BAL) fluids. The protein and albumin concentration increased (p <.05) in the second half of the exposure period, indicating changes in the transudation kinetics of serum proteins into the alveolar lumen. The relative levels of methionine sulfoxide and carbonyl groups in the BAL protein, indicators for oxidative reactions in the respiratory tract, were lowered (p <.03) immediately after the beginning of chronic sulfur(IV) exposure. This indicates either a lowered oxidant burden andlor an increased antioxidant capacity in the lungs. The enzyme β-N-acetylglucosaminidase increased significantly (p <.05) in the EAL fluid. This increase might be due to enhanced release of Iysosomal compounds mediated by sulfite. It did not result from damage of BAL cells, since their viability was not impaired during exposure. Alveolar macrophages (AM) showed a lowered in vitro phagocytosis rate (p<.05) for polystyrene particles and a reduced production (p <.05) of oxygen-derived free radicals after stimulation with opsonized zymosan. These results indicate a reduction in the nonspecific defense capacity of the AM. In conclusion, chronic exposure to an S(IV) aerosol at low concentration might initiate pathobiochemical pathways in the lungs, indicating a potential health hazard.