Vectorial secretion of extracellular matrix proteins, matrix-degrading proteinases, and tissue inhibitor of metalloproteinases by endothelial cells.

In a study of the vectorial secretion of proteins by bovine aortic arch endothelial cells, we found that the extracellular matrix macromolecules collagen and fibronectin as well as several matrix-degrading metalloproteinases were secreted selectively in the basal direction. In contrast, the tissue inhibitor of metalloproteinases showed only a weak preference for the basal direction. Three proteins at 18-35 kDa were secreted with preference apically, counter to the basal secretion of approximately 70% of the total secreted protein. As expected, rabbit synovial fibroblasts, which were used as a control, secreted proteins, including collagen, gelatin-degrading proteinases, and casein-degrading proteinases, equally in apical and basal directions. The basal secretion of collagen, fibronectin, gelatinases, and tissue inhibitor of metalloproteinases by bovine aortic arch endothelial cells suggests that the structural and functional polarity of these cells is manifested, in part, at the level of polarized secretion of matrix-related proteins.