The cyclooxygenase and lipoxygenase pathways that produce prostaglandins (PGs) and hydroxyeicosatetraenoic acids (HETEs) were studied in inflamed rabbit cornea. A cryogenic lesion was induced and five days later the epithelium, stroma and endothelium were isolated and incubated with [1-14C]arachidonic acid. After lesioning, the arachidonic acid metabolites, thromboxane B2, PGF2 alpha and 6-keto-PGF1 alpha exhibited the greatest increase in the stroma. Lipoxygenase products were formed in the three layers also, although 12-HETE predominated. The correlation between the synthesis of these compounds and corneal injury is discussed.

Plasmin can degrade fibronectin and laminin, two important components of the extracellular matrix facilitating cell sliding and healing following a wound. In this study we investigated the relationship between the tear fluid level of plasmin and plasminogen activator and the healing of a corneal wound. Anterior keratectomy (AKE) was performed for seven rabbits (11 eyes). Eight eyes were rewounded after re-epithelialization. Tear fluid samples were collected with capillaries before wounding and during wound healing. Plasmin and plasminogen activator (PA) activities were determined using radial caseinolysis procedures. After AKE the plasmin concentrations increased rapidly, from a mean (+/- SEM) of 3.9 +/- 0.9 micrograms/ml to a mean of 37.9 +/- 7.8 micrograms/ml (p less than 0.01), and decreased during wound healing. Rewounding also resulted in an increase in plasmin concentration in the tear fluid (from a mean of 2.9 +/- 0.6 micrograms/ml to a mean of 5.0 +/- 1.1 micrograms/ml; p greater than 0.05). The PA activity showed an inverse trend as it decreased after AKE from a mean of 2.0 +/- 0.6 IU/ml to a mean of 0.3 +/- 0.1 IU/ml (p less than 0.001). During wound healing and re-epithelialization, the PA activity increased again, to 2.1 +/- 0.3 IU/ml (p less than 0.001). Abrasion of the newly grown epithelium in eight eyes caused a second elevation of PA activity which was not significant. This study demonstrates a close association between the healing of corneal wounds and changes in the plasmin and PA activities in tear fluid. Determination of the activity of these enzymes may therefore be useful for monitoring corneal wound healing.

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