[Type III pneumocyte. The alveolar brush-border cell in rat lung. Study by transmission electron microscopy (author's...

The type III pneumocyte or alveolar brush-border cell was studied in the normal adult rat by transmission electron microscopy. The observation of thick sections and the technique with alcian blue-lanthanum nitrate gave precisions on the fine structure of this cell by revealing the existence of pinocytotic micro-vesicles, of basal ergastoplasm and the proximity of unmyelinated nervous fibres. The different morphological data were confronted with the hypothesis of this cell playing an alveolar chemoreceptive part. Different appearances of the cell body of the type III pneumocyte suggest on the other hand contractile properties of a not well known determinism. Present data concerning the origin of this cell are discussed.