Determination of plasminogen activator activities in normal and pathological human tears. The significance of tear plasminogen activators in the inflammatory and traumatic lesions of the cornea and the conjunctiva

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Abstract
Plasminogen activator activity in normal human tears was found to be 0.03 ± 0.02 IU/ml with casein plate, and 0.06 ± 0.04 IU/ml with a spectrophotometric method. Elevated levels of plasminogen activator activity (range 0.11‐2.05 IU/ml) were detected in the tear fluid of patients suffering from various corneal and conjunctival diseases including corneal ulcers, superficial keratitis, persistent epithelial defects, recurrent erosions, bullous keratopathy, contact lens associated erosions, alkali burns of the cornea, Mooren's ulcer, conjunctival pemphigoid, acute keratoconus, and corneal melanoma. Plasminogen activator activity, determined in the absence of fibrin in tear samples collected by capillary tubes at low flow rates, is considered to be the result of the presence of urokinase‐type plasminogen activator (uPA) deriving from the epithelial cells of the cornea and the conjunctiva. It is suggested that an increase in the level of uPA in tears plays an important role not only in ulceration (the formation and repair of epithelial and stromal defects), but also in the development and healing of a number of other inflammatory processes, infections, immunological processes, chemical burns, contact lens associated lesions; in the invasion of microorganisms and leukocytes, in edema formation, in neovascularization, and in the invasive growth of tumors in the cornea and the conjunctiva.