Oxidative stress is defined as ROS in excess of antioxidant defense mechanisms. Oxidative stress can result from an excess of ROS, a reduction in antioxidants, or both. Damage attributable to oxidative stress is widespread, and oxidative stress is recognized as a prominent feature in numerous disease processes, including neoplasia and heart disease, as well as trauma and burns.1–3 Reactive oxygen species are produced endogenously and exogenously, and elaborate antioxidant defense mechanisms have developed in aerobic organisms to limit the damage caused by ROS.
It is debatable whether ROS are causative or an epiphenomenon of a specific disease process. Determination of causation depends on elucidating the specific damage caused by ROS and measuring the effect of treatment on the degree of oxidative stress and the progression of disease. Assessment of oxidative stress includes measurements of endogenous antioxidants or ROS, evaluation of damage caused by ROS, or a combination of these. Because there are numerous ways to assess oxidative stress but no standardization for these measurements, it is difficult to evaluate the clinical pharmacologic effect of antioxidants.4 In addition, much of the research on assessment of oxidative stress involves methods that are not directly applicable or are not practical in clinical situations. Newer diagnostic methods, such as measurement of urinary concentrations of isoprostanes, are sensitive, specific, noninvasive, and clinically applicable.4
Treatment for oxidative stress includes augmenting endogenous antioxidants, decreasing ROS generation, or scavenging existing ROS. Research on antioxidant supplementation has yielded conflicting results, mainly because of a lack of standardization in testing methods and for dosages and routes of administration.5 The information provided here is intended to review the pathophysiologic processes of oxidative stress, physiologic defense mechanisms against antioxidants, and assessment of oxidative stress in dogs and cats.
Reactive oxygen species
Reduced form of nicotinamide adenine dinucleotide phosphate
Polyunsaturated fatty acid
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