A comparison of the biological activities of the cell-adhesive proteins vitronectin and fibronectin

The effects of vitronectin and fibronectin upon the attachment and growth of bovine corneal endothelial cells (BCE) and BHK-21 cells were compared. Similar dose-response curves for cell attachment to the substratum were obtained for both molecules and both cell types, although BCE cells exhibited a slight preference for vitronectin, and BHK cells for fibronectin. When, however, cells were plated in medium containing bovine serum stripped of fibronectin, they attached and grew normally, whereas in medium containing serum stripped of vitronectin, cells either failed to attach (BHK-21) or attached but exhibited poor cell spreading and growth. This dependence of cells upon vitronectin, rather than fibronectin, in serum for cell attachment, was shown to be due to a failure of fibronectin to coat the substratum in the presence of other serum proteins. Vitronectin was able to coat the substratum efficiently in the presence of other serum proteins. Although dependent upon vitronectin for adhesion to the substratum, bovine endothelial cells were unable to synthesize endogenous vitronectin.