[Possibility of formation of "brush" cells from Type II alveolocytes in rats]

It was found that during acute alveolar hypertrophy (days 5-7 after lefthanded pneumonectomy) the number of alveolar brush cells considerably increases. Alveolocytes were disclosed to accumulate at that particular time in the epithelial lining of the alveoli. They consist of type II alveolocytes, brush cells and of intermediate-type alveolocytes. The latter ones were oval or cuboid in shape, had light cytoplasm with abundant polysomes, 1-4 osmiophilic lamellar bodies, as well as microfibrils and pinocytic vesicles. On the apical plasmalemma of the alveolocytes one could see the initial stages of the formation of cylindrical microvilli and microfibrils. The topography and ultrastructure of the intermediate-type alveolocytes may be viewed as evidence of the formation of the brush alveolocytes from type II alveolocytes.