Corneal diffusion and metabolism of 12 (R) -hydroxyeicosatetraenoic acid (12(R)HETE)

PURPOSE: To quantify the corneal diffusion and metabolism of tritiated 12(R)-hydroxyeicosatetraenoic acid (12(R)HETE) in the in vitro-mounted rabbit cornea to determine if this compound or one of its metabolites can diffuse across the stroma to the corneal endothelium. METHODS: The studies were performed in a Lucite block perfusion chamber by placing tritiated 12(R)HETE on the tear side of the cornea under the following conditions: (A) cornea completely intact (endothelium and epithelium present); (B) cornea with epithelium removed; and (C) cornea with both epithelium and endothelium removed. Radioactivity of 12(R)HETE and metabolites were measured in the different corneal layers and in the corneal perfusates using scintillation spectroscopy. 12(R)-hydroxyeicosatetraenoic and its metabolites were then quantified in the tissue perfusates using high performance liquid chromatography (HPLC) analysis. RESULTS: 12(R)HETE is rapidly taken up and metabolized by the intact cornea to a number of more polar compounds including a metabolite which has spectral and retention time characteristics of 8(R)-hydroxyhexadecatrienoic acid (8(R)HHDTrE). Both 12(R)HETE and 8(R)HHDTrE can diffuse through the stroma to the endothelium. Corneas having the epithelium removed also allow diffusion of 12(R)HETE across the stroma; however, there is significantly less metabolism. When both the epithelium and endothelium are removed, 12(R)HETE is capable of diffusing across the stroma; however, there is little metabolism, which suggests that the majority of 12(R)HETE metabolism occurs in the epithelium and, to a lesser degree, in the endothelium and stroma. CONCLUSIONS: 12(R)HETE and its metabolites are capable of diffusing from the epithelium through the cornea where they may adversely affect the endothelium.