Inhibition of hydroxyl radical formation by human tears.

摘要: The effect of human tears on oxygen radical formation was investigated using xanthine-xanthine oxidase as the generating system. Superoxide (O2.-) and hydrogen peroxide (H2O2) were measured ferricytochrome c indicator. OH. monitored by measuring hydroxylation salicylate. Addition traces iron (Fe3+) chelator (EDTA) a prerequisite for in this Human did not detectably affect O2.- or H2O2 but markedly inhibited formation. Tears obtained from eight different individuals all showed marked inhibitory formation, whereby only small individual variation observed. During separation gelfiltration Sephadex G75 column, three protein peaks eluted column. first contained lactoferrin, second yet unidentified material, third lysozyme. Inhibitory activity coincided with peak also fractions eluting after containing major inhibition seen these latter fractions, which contain organic anorganic substances. fact that ascorbic acid could be detected it investigation's assay system indicates compound involved observed low molecular weight effect. Analysis various cations suggested largely ascribed to tear calcium. Tear calcium binds EDTA thus possibly prevents essential catalytic iron-EDTA complex. Experiments purified milk lactoferrin showed, protein, is abundantly present tears, can inhibit model used here. counteracted increasing concentration reaction mixtures. These findings suggest may play an important role protection ocular surface against induced damage.