Changes in lung volumes and diffusing capacity in guinea pigs exposed to a combination of sulfur dioxide and submicron zinc oxide mixed in a humidified furnace

Abstract

Male Charles River Hartley guinea pigs were exposed for 3 hr to zinc oxide (ZnO) aerosols alone (7.8 mg/m 3) and to various concentrations of ZnO (0.8, 2.7, or 6.0 mg/m 3) in combination with sulfur dioxide (SO 2). The ZnO aerosols ( CMD 0.05 μm, σg 2.0) were generated by the condensation of supersaturated vapors and mixed with SO 2 in a water vapor-saturated furnace at 480°C. We evaluated ventilation, lung mechanics, lung volumes, diffusing capacity for carbon monoxide ( DL CO), and alveolar volume ( VA) in anesthetized, tracheostomized animals after exposure to the aerosols. Breathing frequency, tidal volume, and pulmonary resistance and compliance were unchanged in all exposed groups. Exposure of animals to ZnO alone resulted in significant decrease in functional residual capacity ( FRC) with only minimal changes in other lung volume subdivisions, DL CO and VA. A dose response was induced in animals exposed to SO 2 and increasing concentrations of ZnO as shown by decreases in lung volumes, DL CO and VA. In animals exposed to the lowest ZnO concentration (0.8 mg/m 3), vital capacity ( VC) was significantly lower while other lung volume parameters, DL CO and VA, were unchanged compared to control values. As the concentration of ZnO was increased, as in the 6.0 mg/m 3 ZnO group, all lung volume subdivisions, DL CO and VA, were significantly decreased. Analysis of collected aerosols during the experiments indicated the presence of sulfate, sulfite, and adsorbed sulfur trioxide, all of which could induce bronchoconstriction in the guinea pig. The nature of the response in this study suggests a reaction in the periphery of the lungs indicating that the various sulfur species were carried into the lung parenchyma by the submicron ZnO particles. The decreased lung volumes, DL CO and VA, indicate alveolar duct constriction probably with the involvement of pulmonary edema.