[Tissue plasminogen activator and plasminogen activator inhibitor in aqueous humor]

In the anterior segment of the eye, fibrin clots must be rapidly resorbed to prevent fibrosis. Tissue-type plasminogen activator (t-PA), a serine protease that catalyzes the conversion from plasminogen to plasmin, plays an important role in the fibrinolytic system and has therefore in recent years attracted attention in the field of ophthalmology.

The aqueous humor of patients undergoing cataract surgery was analyzed for the presence of components of the fibrinolytic cascade. The quantities of t-PA and plasminogen-activator inhibitor (PAI) were determined using enzyme-linked immunosorbent assays. We determined t-PA and PAI in the aqueous humor of 64 patients between 59 and 82 years of age.

The t-PA levels ranged from 0.65 to 1.75 ng/ml and PAI activity from 3.24 to 5.1 AU/ml. Association between t-PA levels and PAI activity and accompanying diseases or metabolic disorders was noted. The highest concentration of t-PA and the lowest activity of PAI has been observed in aqueous humor of patients with senile cataract. The knowledge about the presence of t-PA in aqueous humor is significant for the recognition of pathological events following intraocular fibrin formation and may be an important basis for therapeutic use of t-PA.