Measurement of ascorbic acid and glutathione peroxidase activity in biological samples collected from recurrent airway obstruction affected horses and their controls.

Abstract

Multiple biomarkers of oxidative stress have been measured and utilized in human medicine to assess the redox status of the lung. The purpose of the study was to determine the relationships between ascorbic acid concentration in bronchoalveolar lavage fluid (BALF), and the activity of cellular glutathione peroxidase (cGPx) in red blood cells (RBC), white blood cells (WBC), and cells of BALF, to distinguish recurrent airway obstruction (RAO)-affected horses from their matched controls. Sixteen horses in matched pairs were used: eight non-RAO-affected (controls) and eight RAO-affected horses. Samples from all horses were collected at remission (S1), during environmental challenge (S2) and at recovery (S3). In RAO-affected horses, RBC cGPx were significantly higher at all sample times (p = 0.0313 at S1, p = 0.0208 at S2, p = 0.0207 at S3). WBC cGPx activity was also greater in these horses during remission (p = 0.0128 at S1) and challenge (p = 0.0087 at S2). In the BALF, RAO-affected horses had significantly higher cGPx activity during recovery compared to remission (p = 0.0077). BALF ascorbic acid concentration (total, free and oxidized) was not significantly different in control horses, but total (p = 0.0009) and free (p = 0.0021) forms were significantly reduced during challenge in RAO-affected horses. The elevation in cGPx concentration suggests an up-regulation of this redox system to combat oxidative stress as the ascorbic acid system is depleted during challenge in RAO-affected horses. This difference supports further research into antioxidant interventions that may prevent or minimize clinical signs of RAO.