title: Complex formation between urokinase and plasma protein C inhibitor in vitro and in vivo.
abstract: Protein C inhibitor (PCI) and plasminogen activator inhibitor 3 (PAI-3; urinary urokinase inhibitor) are immunologically identical. The role of PCI for urokinase (uPA) inhibition in vivo was investigated. We therefore developed an enzyme-linked immunosorbent assay (ELISA) specific for uPA-PCI complexes: Rabbit anti-PCI IgG was immobilized on a microtiter plate and following incubation with uPA-PCI complex-containing samples, bound uPA-PCI complexes were quantified with a horseradish-peroxidase-linked monoclonal antibody (MoAb) to uPA. Using this assay, time, dose, and heparin-dependent complexes were detected when uPA was incubated with normal plasma or purified urinary PCI, whereas no complexes were measurable using PCI-immunodepleted plasma. Plasma samples (containing 20 mmol/L benzamidine to prevent complex formation ex vivo) from patients undergoing systemic urokinase therapy (1 x 10(6) IU/60 min intravenously [IV]) after myocardial infarction were also studied. uPA present in these plasma samples (up to 1,200 ng/mL) had only 43% to 70% of the specific activity of purified 2-chain uPA, suggesting that a major portion of uPA is complexed to inhibitors. In these plasma samples uPA-PCI complexes were present in a concentration corresponding to 21% to 25% of inactive uPA antigen. These data suggest that at high uPA concentrations, such as during uPA therapy, plasma PCI might contribute significantly to uPA inhibition in vivo.
authors.affiliation: Department of Medical Physiology, University of Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Geiger
authors.forename: K
authors.initials: K
authors.lastname: Huber
authors.forename: J
authors.initials: J
authors.lastname: Wojta
authors.forename: L
authors.initials: L
authors.lastname: Stingl
authors.forename: F
authors.initials: F
authors.lastname: Espana
authors.forename: J H
authors.initials: JH
authors.lastname: Griffin
authors.forename: B R
authors.initials: BR
authors.lastname: Binder
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay; D006493:Heparin; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D011480:Protease Inhibitors / Q000097:blood / Q000378:metabolism* / Q000652:urine; D011486:Protein C / Q000037:antagonists & inhibitors*; D014568:Urokinase-Type Plasminogen Activator / Q000097:blood / Q000378:metabolism* / Q000627:therapeutic use
chemical_list: D046911:Macromolecular Substances; D011480:Protease Inhibitors; D011486:Protein C; D006493:Heparin; D014568:Urokinase-Type Plasminogen Activator