Human endothelial cells produce a plasminogen activator inhibitor and a tissue-type plasminogen activator-inhibitor complex.
Serum-free conditioned media and cell extracts from cultured human umbilical vein endothelial cells were analyzed for plasminogen activator by SDS-polyacrylamide gel electrophoresis and enzymography on fibrin-indicator gels. Active bands of free and complexed tissue-type plasminogen activator (t-PA) or urokinase-type plasminogen activator (u-PA) were identified by the incorporation of specific antibodies against, respectively, t-PA or u-PA in the indicator gel. The endothelial cells predominantly released a high-molecular-weight t-PA (95 000-135 000). This t-PA form was converted to Mr-72 000 t-PA by 1.5 M NH4OH/39 mM SDS. A component with high affinity for both t-PA and u-PA could be demonstrated in serum-free conditioned medium and endothelial cell extract. The complex between this component and Mr-72 000 t-PA comigrated with high-molecular-weight t-PA. From the increase in Mr of t-PA or u-PA upon complex formation, the Mr of the endothelial cell component was estimated to be 50 000-70 000. The reaction between t-PA or u-PA and the plasminogen activator-binding component was blocked by 5 mM p-aminobenzamidine, while the complexes, once formed, could be cleaved by 1.5 M NH4OH/39 mM SDS. These observations indicated that the active center of plasminogen activator was involved in the complex formation. It was further noted that serum-free conditioned medium or endothelial cell extract inhibited plasminogen activator activity when assayed by the fibrin-plate method. Evidence is provided that the plasminogen activator-binding component was different from a number of the known plasma serine proteinase inhibitors, the placenta inhibitor and the fibroblast surface protein, proteinase-nexin. We conclude that cultured endothelial cells produce a rapid inhibitor of u-PA and t-PA as well as a t-PA-inhibitor complex.
D016564:Amyloid beta-Protein Precursor; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004727:Endothelium / Q000378:metabolism*; D006023:Glycoproteins / Q000096:biosynthesis*; D006801:Humans; D008970:Molecular Weight; D010960:Plasminogen Activators / Q000037:antagonists & inhibitors*; D015849:Plasminogen Inactivators; D058255:Protease Nexins; D011817:Rabbits; D011956:Receptors, Cell Surface
D016564:Amyloid beta-Protein Precursor; D002352:Carrier Proteins; D006023:Glycoproteins; D015849:Plasminogen Inactivators; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D010960:Plasminogen Activators