The cytoskeleton and the extracellular matrix in sensitized canine tracheal smooth muscle

To investigate the mechanisms responsible for the increased shortening capacity (delta Lmax) of airway smooth muscle in ragweed pollen sensitized dogs, the alterations of biophysical and biochemical properties of cytoskeleton and extracellular collagen in tracheal smooth muscle (TSM) were studied. Smooth muscle passive elastic properties were not significantly altered by removal of cytoskeleton with guanidine HCI plus 2-mercaptoethnol; collagenase digestion reduced smooth muscle force development, but did not affect its delta Lmax and passive elastic properties in both sensitized and control dogs. There were no significant differences in the amount of cytoskeletal intermediate filament proteins, desmin and vimentin between sensitized and control TSM. The content of total collagen, collagen type I, and collagen cross-linking in sensitized TSM were significantly greater than in control. Collagen fibres in sensitized TSM was more resistant to collagenase attack. We conclude that increased delta Lmax in sensitized canine TSM is not the result of alterations in passive cytoskeletal and extracellular collagen structures.