Measuring free radical reactions in vivo.

The increasing interest in the role of free radicals in the pathogenesis of human disease has led to an increased need for techniques to measure free radicals and their reactions in vivo and, most importantly, in the clinical situation. Free radicals are extremely reactive and thus short lived. Consequently, free radicals are not amenable to direct assay and free radical activity is usually assessed by indirect methods such as measurement of the various end products of reactions with lipids, proteins and DNA. A vast array of analytical techniques has been developed to measure these end products though not all of them are applicable to the clinical situation where the only samples normally available are blood, urine and expired breath. Lipid peroxidation is the most intensively studied process and provides a number of possibilities for assays. Protein and nucleic acid oxidation are attracting increasing attention at the present time. The techniques currently available, however, are limited to semi-quantitative assays of damage to broad classes of biomolecules and there is an urgent need for more specific and informative methods.