The resistance of epithelia to vascularization: Proteinase and endothelial cell growth inhibitory activities in urinary bladder epithelium |
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Authors: | Beverly Waxler Klaus E Kuettner Bendicht U Pauli |
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Institution: | 2. Department of Pathology, Rush Medical College, Rush-Presbyterian-St Luke''s Medical Center, Chicago, Illinois 60612 USA;1. Departments of Biochemistry and Orthopedic Surgery, Rush Medical College, Rush-Presbyterian-St Luke''s Medical Center, Chicago, Illinois 60612 USA |
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Abstract: | 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 μg 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. |
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Keywords: | Bladder epithelium proteinase inhibitor endothelial cell growth inhibitor tissue culture |
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