TEAR FLUID CONTENT OF ELECTROCHEMICALLY ACTIVE COMPONENTS INCLUDING WATER-SOLUBLE ANTIOXIDANTS

Purpose. To describe the content of water-soluble antioxidants in tear fluid. Methods. We collected tear fluid from healthy subjects, either into borosilicate glass tubing or by absorption onto Schirmer strips. High pressure liquid chromatography with electrochemical detection pr ovided data on several components in a single assay. The system was su fficiently sensitive to provide reliable values for components present in tear fluid collected at normal (basal) or stimulated rates of secr etion. Results. Tear fluid at basal secretion was found to contain fou r compounds often considered to function in biology as antioxidants. A scorbic acid (AA) is found at 665 mu M, tyrosine at 45 mu M and glutat hione (GSH) at 107 mu M. Cysteine (48 mu M) and uric acid (328 mu M) a re reported for the first time; the latter is somewhat controversial a s a physiologically active antioxidant. One peak on the chromatogram w as consistently present but has not been identified. During stimulatio n of flow by brief inhalation of ammonium hydroxide fumes, the concent ration of each compound was lower. Conclusion. This work demonstrates the presence of electrochemically active components that might functio n as antioxidants at the anterior surface of the cornea against potent ial damage from radiation, oxygen toxicity, abrasion and environmental chemicals.