Measurement of ascorbic acid concentration and glutathione peroxidase activity in biological samples collected from horses with recurrent airway obstruction

Objective-To measure the ascorbic acid (AA) concentration in bronchoalveolar lavage fluid (BALF) and cellular glutathione peroxidase (cGPx) activity in RBCs and WBCs from peripherally obtained blood and in cells from BALF to determine whether differences existed between the 2 major redox systems in recurrent airway obstruction (RAO)-affected and -nonaffected (control) horses and between systemic and local pulmonary responses in the glutathione redox system Animals-16 adult horses in pairs 8 healthy (control) and 8 RAO-affected horses Procedures-Physical examination data and biological samples were collected from horses before (remission) during and after (recovery) environmental challenge with dusty straw and hay At each stage BALF cell AA concentration and RBC WBC and BALF cell cGPx activity were measured Results-Compared with control horses RAO affected horses had significantly higher cGPx activity in RBCs at all points and in WBCs during remission and challenge The BALF cell cGPx activity was higher in RAO-affected horses during recovery than during remission The BALF cell AA concentration did not differ significantly in control horses at any point but total and free AA concentrations were significantly lower in RAO-affected horses during the challenge period than during remission and recovery periods Conclusions and Clinical Relevance-High cGPx activity suggested this redox system was upregulated during exposure to dusty straw and hay to combat oxidative stress as AA was depleted in RAO-affected horses The relative delay and lack of comparative increase in cGPx activity within the local environment (represented by BALF cells) compared with that in RBCs and WBCs might contribute to disease in RAO-affected horses (Am J Vet Res 2010 71 1500-1507)