This proposal is a continuation of our ongoing studies on lipid metabolism in the cornea focusing on the modulation of the release and metabolism of lipid mediators from membrane phospholipids during inflammation.  The metabolism of 1-O-alkyl-2 acetyl-sn- glycerophosphocholine (platelet activating factor, PAF) will be studied in the rabbit cornea, including its de novo synthesis and the PAF cycle.  We will test three hypotheses: a) the PAF cycle is altered during corneal injury; b) the synthesis of hydroxyeicosatetraenoic acid by lipoxygenation and other pathways is a major branch of the arachidonic acid cascade during anterior segment inflammation; and c) the PAF cycle and the arachidonic acid cascade are interrelated in the inflammatory response after corneal injury.  Two models of inflammatory will be used: a cryogenic and an alkali burn model.  Both models have been characterized with respect to the formation of prostaglandins and lipoxygenase products during the tenure of this grant.  The metabolism of PAF and eicosanoids will be followed in vivo after intracameral injection of precursors.  Another goal of this proposal is to determine the cellular origin of these metabolites and the interaction between cells that are intrinsic to the cornea and cells that arrive after injury.  Powerful analytical procedures such as high performance liquid chromatography capillary gas-liquid chromatography, and gas chromatography-mass spectrometry, will be used.  Correlations with histology and biological activity by platelet aggregometry as a bioassay system will be made.  Several drugs will also be evaluated to assess their sites of action and to correlate their biochemical effects with the clinical evolution of corneal injury.  The results obtained will define the involvement of PAF and arachidonic acid metabolism, and of lipoxygenase reaction products in particular, in anterior segment inflammation and in corneal wound healing.