Differential distribution of ciliated epithelial cells in the trachea of hamsters: implications for studies of pathogenesis.

The morphology of the inner aspect of the adult hamster trachea was examined by scanning electron microscopy. Relatively large patches of unciliated cells were observed in the epithelial layer. The patches, which covered several hundreds to thousands of square microns, were most conspicuous on the ventral surface of the trachea, especially in the middle third. The frequency of these areas of unciliated cells, both isolated and in patches, was much greater in hamsters than in mice, rats, or cats. Greatest ciliation in the hamster trachea was observed over the strip of trachealis muscle between the open ends of the cartilaginous rings. Areas with the heaviest ciliation also had the greatest activity of cellular metabolism, as measured by the tetrazolium reduction assay. The attachment of tritium-labeled cells of Mycoplasma pneumoniae was inversely correlated with extensive ciliation, since the greatest numbers of counts were found on the middle third and ventral regions of the tracheal surface. The results of this study suggest that the regional differences in ciliation of respiratory epithelium in hamsters may influence studies of pathogenesis and isolation of M. pneumoniae and that these differences should therefore be considered and controlled in the experimental design.