Considerations on the origin and ultrastructural aspects of type II pneumocytes under normal conditions and endotoxic shock experimentally induced in dogs.

On the basis of the morphological aspects found during a series of experimental investigations on the ultrastructural aspects of the lung under shock in the dog, the authors deny that type II pneumocytes belong to the group of alveolar macrophages and maintain that they are of an epithelial nature. This is confirmed by the presence of desmosomal junctions with the type I pneumocytes. In the "shock lung" induced by Escherichia Coli endotoxin, the type II pneumocytes appear to be severely damaged with particular involvement of the osmiophilic inclusions, sites of synthesis and/or heaping up of the principal phospholipidic constituents of the surfactant system.