ELEVATION OF TRANSFORMING GROWTH-FACTOR-ALPHA IN CAT AQUEOUS-HUMOR AFTER CORNEAL ENDOTHELIAL INJURY

Purpose. To determine if a scrape injury to cat corneal endothelial ce lls increases the level of mitogenic proteins such as transforming gro wth factor alpha (TGF alpha) in aqueous humor. Methods. Aqueous humor of cats was collected at 0, 2, 6, and 24 hours after wounding the endo thelium by contact with a cannula tip. Aqueous humor samples collected from sham-wounded cats served as controls. Aqueous humor samples were analyzed for levels of protein, for mitogenic activity using incorpor ation of tritiated thymidine by cultures of bovine corneal endothelial cells, and for immunoreactive TGF alpha protein using a specific radi oimmunoassay. Results. The average protein level in aqueous humor obta ined before wounding was low (0.5 mg/ml), increased 26-fold at 2 hours after injury (13 mg/ml), then progressively decreased at 6 hours (8 m g/ml) and 24 hours (2 mg/ml). Levels of mitogenic activity of aqueous humor samples collected 2, 6, and 24 hours after wounding were 2-fold, 2.5-fold, and 0.6-fold higher, respectively, compared to the level of mitogenic activity measured in aqueous humor collected before woundin g (0 hours) or in aqueous humor collected from sham-wounded eyes. TGF alpha concentration in aqueous humor collected before endothelial woun ding was low (6.8 ng/ml), increased 14-fold 2 hours after wounding (97 .4 ng/ml), then progressively decreased at 6 hours (63.3 ng/ml) and 24 hours (35.5 ng/ml) after wounding. TGF alpha concentrations in aqueou s humor collected from sham-wounded eyes at 2 hours (9.5 ng/ml) and 6 hours (5.3 ng/ml) were not significantly different from prewound level s. Detergent extracts of bovine corneal endothelial cells contained su bstantial levels of TGF alpha immunoreactive protein (20 ng/mg protein ). Conclusions. Wounding of cat endothelium causes a rapid increase in mitogenic proteins in aqueous humor including TGF alpha, which may ac t by an autocrine mechanism to stimulate endothelial wound healing.