Ultrastructure of hamster and rat lungs after chronic inhalation exposure to cadmium compounds

During chronic inhalative exposure to Cd compounds (CdCl2, CdS04, Cd0 and CdS) proliferation of type II pneumocytes seems to be an early event in both species. In the hamster they seem to differentiate into type I epithelium and Clara cells (and possibly ciliated cells). For unknown reasons the latter pathway must be at least partially inhibited in the rat. This results in the persistence of type II cells that may undergo transformation and give to preneoplastic and neoplastic lesions.