The effect of ammonia on the respiratory nasal mucosa of mice. A histological and histochemical study.

The effects of prolonged exposure to ammonia vapour on the histological pattern and enzymatic activity of the respiratory nasal mucosa of 75 adult male mice were investigated and compared with a control group. In the exposed animals, the nasal epithelial cells showed patches of squamous metaplasia, dysplasia, and even malignant changes in the nose of 2 animals. As regards the histochemical changes, the apical border of epithelial cells showed increased succinic dehydrogenase activity denoting increased energy production. The acid phosphatase activity was also higher, and this seemed to be a constant feature in metaplastic and neoplastic transformation. The alkaline phosphatase activity was detected only in the basal parts of epithelial and goblet cells, which was attributed to an increased activity of basal cells to form a thicker basement membrane. The periodic acid Schiff's reaction was weak in the cilia due to their partial degeneration. Prolonged exposure to ammonia interfered with the normal physiological mucociliary action resulting in accumulation of particulate matter initiating or promoting a neoplastic process.