[Morphologic changes in lung tissue in mice after long-term exposure to NO2]

The light microscopical, histochemical and ultrastructural changes induced by NO2 were studied in lung tissue of experimental mice. The animals were daily exposed to NO2 for one hour and after 12 days we observed focal light microscopical changes (dilatation of alveolar crypts, minute inflammatory infiltrates). A rather high point activity of acid phosphatase was found, particularly in the cytoplasm of alveolar and septal macrophages. The light microscopical findings were supported by ultrastructural changes, i.e. vacuolation up to disintegration of alveolar pneumocytes, multiplication of macrophages, thickening of alveolar septa with multiplication of collagenous fibrils and infiltrate consisting of lymphocytes and plasma cells. The endothelium of capillaries displayed vacuolation and thickening of basal membrane in some sections. The quantitative examination showed multiplication of goblet cells in the epithelium of bronchial stroma of experimental animals compared to the controls. No morphological changes in the myocardium of the control group were observed even at ultrastructural level.