Increased basal levels of free plasminogen activator activity found in human aqueous humor.
OBJECTIVE
To quantify the basal free t-PA activity in human aqueous humor.


METHODS
Human aqueous humor obtained by simplified pipette paracentesis at cataract surgery was tested for free t-PA activity in a revised 15-hour amidolytic assay using a t-PA standard curve (n = 15). Total antigenic levels of PAI-1, the principal PA inhibitor, were determined using an ELISA kit. The available PAI-1 activity was tested indirectly using anti-human PAI-1 antibody blocking before t-PA activity assay (n = 11). Plasminogen activator type was determined by anti-human t-PA and urokinase (u-PA) antibody blocking before activity assay (n = 7).


RESULTS
Free PA activity ranged widely (0.072 to 0.47 IU/ml; mean, 0.20 +/- 0.10 IU/ml) and was almost completed inactivated (> or = 89%) by antibody against human t-PA but not by the u-PA antibody. PAI-1 total antigen also ranged widely between (0.25 to 8.0 ng/ml; mean, 2.25 +/- 2.54 ng/ml). However, pretreatment of samples with PAI-1 antibody or by acidification (pH 3.2) to inactivate inhibitors did not increase t-PA activity levels.


CONCLUSIONS
A basal-free t-PA activity, which is predominantly t-PA, is present in human aqueous humor at approximately 20 times higher levels than previously found with an earlier assay. This activity is estimated to represent roughly 10% of total released t-PA antigen. PAI-1 is present in aqueous humor at levels considerably lower than reported values for plasma in a predominantly PA-complexed or inactive form.
Wang
Y
Y
Department of Pathology, University of Connecticut Health Center, Farmington 06030-3105.
Taylor
D M
DM
Smalley
D M
DM
Cone
R E
RE
O'Rourke
J
J
D000368:Aged; D000369:Aged, 80 and over; D001082:Aqueous Humor / Q000737:chemistry*; D002387:Cataract Extraction; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008875:Middle Aged; D017395:Plasminogen Activator Inhibitor 1 / Q000032:analysis; D010959:Tissue Plasminogen Activator / Q000032:analysis*
D017395:Plasminogen Activator Inhibitor 1; D010959:Tissue Plasminogen Activator