Immobilization and ultrastructure of alveolar type II cells.

We studied the ultrastructural changes in the alveolar type II cells from the lung of immobilized male Wistar rats divided into 6 groups: control; immobilized for 1, 12, 24 and 30 hours; immobilized for 30 hours and readapted for 5 hours. We used the routine methods of fixation through perfusion and electron microscopy. The results indicated progressive structural changes in the alveolar type II cells, correlating with a prolonged time of akinesia. Characteristic was the swelling affecting first the mitochondria and then all other organelles and the plasmalemma. Hypertrophy and hyperplasia of the lamellar bodies were clearly seen. The relatively quick recovery suggested the accelerated mitosis of the alveolar type II cells.