The morphologic changes of the rat type II pneumocytes induced by oxytetracycline.

Ultrastructural changes in pulmonary alveoli of adult Sprague-Dawley rats administered oxytetracycline (1 mg. per ml.) in their drinking water were compared with those of control rats whose drinking water contained no antibiotics. Groups of rats were sacrificed after 4 and 8 weeks of oxytetracycline treatment. Type II pneumocytes of oxytetracycline-treated rats showed an increase in size and number of lamellar bodies, as well as in their cell volume, when compared with controls. Electron microscopic morphometry confirmed these findings; the lamellar inclusion bodies increased 6 and 10 per cent and the cell volume increased 3 and 5 per cent at 4 and 8 weeks, respectively. The type I pneumocyte and alveolar macrophage showed engulfed myelin figures, and the Clara cells appeared quiescent. These findings suggest that the type II pneumocyte hypertrophy can be induced independently from the diffuse alveolar damage. The oxytetracycline treatment may provide a model system in which the pathologic morphology and function of the type II pneumocyte can be studied independently.