EDTA-mediated separation of cat tracheal lining epithelium.

After specimens of cat trachea were incubated for 2 hr in 20 mM EDTA, the epithelium could easily be stripped from the mucosal surface with a dissecting needle. The epithelium was cleanly separated from its basal lamina, which remained fixed to the lamina propria. Epithelial cells were well preserved, junctional complexes were structurally intact, and there was no widening of intercellular spaces. The inferior epithelial surface was irregular, with numerous membrane-bound blebs arising from the constituent epithelial cells. Hemidesmosomes, which are found only on basal cells, were covered by a nap of fine filaments, the remnants of the filaments that normally traverse the lamina lucida. In many basal cells, cleaved hemidesmosomes were internalized, probably representing a stage in their lysosomal degradation. The basal lamina adhering to the lamina propria appeared in the transmission electron microscope as a sinuous linear density. In the scanning electron microscope, the basal lamina surface had an irregularly corrugated appearance. The basal lamina continued into the stomata of the submucosal gland ducts, which intersected the surface at an acute angle. Anchoring fibrils identical to those associated with stratified squamous epithelium were found in significant numbers on the connective tissue face of the basal lamina. Separation of tracheal tissues may provide a means whereby secretory activity and products of epithelium and submucosal glands can be individually assessed.