Morphometric Evaluation of Ultrastructural Changes in Type II Alveolar Cells of Rat Lung Produced by Bromhexine

The influence exerted by the secretolyticum Bisolvon® on rat lungs was examined. The lungs were fixed for electron microscopy by vascular perfusion of the fixatives in order to preserve the extracellular lining layer of alveoli (surfactant). The appearance of this lining layer was identical in Bisolvon-treated animals as compared with controls. But in Bisolvon-animals peculiar, unusually large forms of lamellated bodies of alveolar cells type II could be observed. A morphometric examination of this material demonstrated that the volume of lamellated bodies within alveolar cells type II, but especially the volume of alveolar epithelial cells type II, as compared with the total volume of lung tissue were clearly increased. The conclusion is drawn that these cells, supposed to represent the major source of alveolar surfactant, proliferate or differentiate under the influence of Bisolvon. The possible significance of this finding for the function of pulmonary surfactant is discussed. Additonally, concentric lamellar bodies, which appear to be proliferations of smooth endoplasmic reticulum, were found in alveolar cells type I.