The resistance of epithelia to vascularization: proteinase and endothelial cell growth inhibitory activities in urinary bladder epithelium.
The avascularity of epithelia may be attributed to the presence of an extractable, low-molecular-weight factor. This factor contains potent inhibitors of proteolytic enzymes, as well as a growth inhibitory activity directed against endothelial cells in vitro. It is extracted from the epithelium of bovine urinary bladders by 1 M NaCl. The extract is ultrafiltered through an Amicon XM-50 membrane, then concentrated and dialyzed into a 0.9% NaCl solution, using a UM-2 membrane. This ultrafiltrate, called the UM-2 retentate (UM-2R), contains approximately 6 micrograms protein/g tissue. The UM-2R has a low content of uronic acid and is practically devoid of hydroxyproline. SDS-PAGE reveals that the UM-2R consists of six major proteins. The UM-2R contains a Trasylol-like proteinase inhibitor that expresses strong trypsin inhibitory activity. Comparisons between bladder and serum UM-2Rs and electrophoretic mobility assays indicate that this proteinase inhibitory activity is derived from the bladder epithelium and not from the serum. The UM-2R is cytotoxic to cultured endothelial cells. Cultures of other cell types (normal and neoplastic) are not affected. The bladder-derived proteinase and endothelial cell growth inhibitory activities may protect epithelia from vascular invasion.
D000818:Animals; D002417:Cattle; D004848:Epithelium / Q000032:analysis / Q000098:blood supply / Q000187:drug effects; D006909:Hydroxyproline / Q000032:analysis; D066298:In Vitro Techniques; D011480:Protease Inhibitors / Q000302:isolation & purification* / Q000494:pharmacology; D011506:Proteins / Q000032:analysis; D001743:Urinary Bladder / Q000032:analysis* / Q000098:blood supply
D011480:Protease Inhibitors; D011506:Proteins; D006909:Hydroxyproline