Corneal PAF acetylhydrolase increases in anterior segment ischemia in rabbits

The involvement of platelet-activating factor (PAF) in the development of anterior segment necrosis after occlusion of the bilateral long posterior ciliary arteries was investigated in rabbits. With the progression of anterior segment necrosis, which was characterized by corneal edema and neovascularization, the contents of protein and total phospholipids increased in the cornea and aqueous humor, but not in the iris. PAF acetylhydrolase activity was significantly increased on the first postoperative day in the peripheral cornea and on the second day in the central cornea prior to the development of marked corneal edema and neovascularization, but it did not increase in the iris. The accumulation of newly synthesized PAF in the cornea reached a plateau level on the third postoperative day, which coincided with the progression of the corneal lesion. In the aqueous humor, PAF acetylhydrolase activity was increased by the induced ischemia, but no PAF was detected. The increased PAF acetylhydrolase activity may reflect adaptation to the participation of PAF in the progression of anterior segment necrosis.