PMID: 8591912Feb 1, 1987Paper

Inhibition of hydroxyl radical formation by human tears

Investigative Ophthalmology & Visual Science
A KuizengaA Kijlstra

Abstract

The effect of human tears on oxygen radical formation was investigated using xanthine-xanthine oxidase as the oxygen radical generating system. Superoxide (O2.-) and hydrogen peroxide (H2O2) were measured using ferricytochrome c as indicator. OH. formation was monitored by measuring the hydroxylation of salicylate. Addition of traces of iron (Fe3+) and chelator (EDTA) was a prerequisite for OH. formation in this system. Human tears did not detectably affect O2.- or H2O2 formation but markedly inhibited OH. formation. Tears obtained from eight different individuals all showed a marked inhibitory effect on OH. formation, whereby only a small individual variation was observed. During separation of human tears by gelfiltration on a Sephadex G75 column, three protein peaks eluted from the column. The first contained lactoferrin, the second as yet unidentified material, and the third lysozyme. Inhibitory activity on OH. formation coincided with the first protein peak and also with fractions eluting after the protein peak containing lysozyme. The major inhibition on OH. formation was seen in these latter fractions, which contain small organic and anorganic substances. The fact that ascorbic acid could not be detected in human tears an...Continue Reading

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