Abstract
Septal cells in the alveolar interstitium of the lung have been assumed to be contractile and involved in the regulation of ventilation/perfusion ratio. We studied two cytoskeletal components of the septal cell in the rat lung. One contains thick microfilament bundles: by decoration with heavy meromyosin, the bundle was shown to be composed of actin filaments of opposite polarity. The other contains intermediate filaments: by pre-and post-embedding immunogold electron microscopy, they were shown to contain both desmin and vimentin. Double labeling immunoelectron microscopy further revealed that some intermediate filaments are co-polymers of desmin and vimentin. The features revealed in the present study support the hypothesis that septal cells can contract and change the architecture of the air-blood barrier.
