Spleen changes in animals inhaling ambient levels of nitrogen dioxide

Abstract

The effects of ambient levels of NO2 on the spleens of adult and newborn Swiss Webster mice were determined. Spleens were evaluated by the following criteria: spleen weight, expressed as a percent of body weight (% spleen wt), size of spleen lymphoid nodules as determined by computed image analysis, spleen cell count and histopathologic evaluation. Data for NO2-exposed animals were compared with data for controls that inhaled filtered air. Control (217) and 217 NO2-exposed animals were studied. After 6 wk of exposure to NO2 at ambient levels (0.35 .+-. 0.05 ppm), the following significant changes were observed in the spleens of exposed mice: increased % spleen wt (P < 0.0025), increased size of spleen lymphoid nodules (P < 0.01), smaller increase in spleen cell number per given weight increment of spleen as determined by correlation coefficients (P < 0.0125) and linear regression analysis of spleen cell counts and an apparently greater predominance of red cells in the red pulp. Inhalation of NO2 was associated with quantifiable spleen changes, which may be useful for assessing effects of inhaled NO2.