title: Tissue plasminogen activator activity in human aqueous humor.
abstract: OBJECTIVE
  To determine the levels of free plasminogen activator activity in human aqueous humor and to identify the type of activity (i.e., tissue-type t-PA or urokinase-type u-PA) that is responsible.
  
  
  METHODS
  Aqueous humor was obtained by a simplified pipette paracentesis before cataract surgery in 31 subjects, ages 57 to 93 years. Levels of plasminogen activator activity were determined using a modified 17-hour specific amidolytic assay. The type of plasminogen activator was investigated in selected samples based on its dependence on soluble fibrin, inhibition by amiloride, and specific antibody blocking. Activity-antigen ratios were compared in seven samples.
  
  
  RESULTS
  Plasminogen activator (PA) activity was present in all samples tested. PA activity ranged widely between 0.54 and 26.7 mIU/ml, with a mean value of 10.8 +/- 8.1 mIU/ml. Soluble fibrin, a known stimulator of tissue-type plasminogen activator (t-PA), was required in the assay system. Its absence decreased the measured activity by more than 90%. Amiloride, a known inhibitor of urokinase-type PA, had little or no effect in selected samples tested. The activity was blocked by anti-human t-PA antibodies but not by antibodies against human u-PA, further defining the type of PA responsible for the detected activity. t-PA antigen levels showed less variation among individuals than did activity levels. Antigen-activity ratios ranged between 89 and 552.
  
  
  CONCLUSIONS
  Plasminogen activator activity is present in the human aqueous humor in measurable quantities. The type of PA activity present is almost exclusively t-PA. t-PA activity varies more widely than antigen, as is the case in plasma.
authors.affiliation: Department of Pathology, University of Connecticut Health Center, Farmington.
authors.forename: D M
authors.initials: DM
authors.lastname: Smalley
authors.forename: J E
authors.initials: JE
authors.lastname: Fitzgerald
authors.forename: D M
authors.initials: DM
authors.lastname: Taylor
authors.forename: R E
authors.initials: RE
authors.lastname: Cone
authors.forename: J
authors.initials: J
authors.lastname: O'Rourke
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000584:Amiloride; D001082:Aqueous Humor / Q000737:chemistry*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005337:Fibrin; D006801:Humans; D008297:Male; D008875:Middle Aged; D010958:Plasminogen; D010959:Tissue Plasminogen Activator / Q000032:analysis*; D014568:Urokinase-Type Plasminogen Activator / Q000032:analysis
chemical_list: D000584:Amiloride; D005337:Fibrin; D010958:Plasminogen; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator