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

This research examines the concentration of ascorbic acid and the activity of the enzyme glutathione peroxidase in horses suffering from recurrent airway obstruction (RAO), a respiratory ailment. The study found significant changes in these components in RAO-affected horses compared to control horses, suggesting the oxidative stress response might play an important role in this disease.

Research Objectives and Methodology

• The main goal of this study was to determine whether there were differences between RAO-affected and healthy control horses in the concentration of ascorbic acid (AA) in bronchoalveolar lavage fluid (BALF) and the activity of the enzyme cellular glutathione peroxidase (cGPx) in red and white blood cells (RBCs and WBCs), as well as cells in the BALF.
• The study also wanted to investigate differences in the systemic (body-wide) and local (lungs) response of the glutathione redox system in these horses.
• The researchers studied a total of 16 adult horses, with eight RAO-affected horses and eight healthy control horses.
• Data and biological samples were collected from these horses at different stages: before exposure to dusty straw and hay (remission), during exposure, and after exposure (recovery).
• At each stage, the researchers measured the AA concentration in the BALF cells and cGPx activity in the RBCs, WBCs, and BALF cells.

Research Findings

• The RAO-affected horses had significantly higher cGPx activity in their RBCs at all stages and in their WBCs during the remission and exposure stages compared to the control horses.
• The cGPx activity in the BALF cells of the RAO-affected horses increased during recovery, as compared to the remission stage.
• While there were no significant changes in the BALF cell AA concentration in the control horses at any point, the RAO-affected horses had significantly lower total and free AA concentrations during the exposure stage than during the remission and recovery stages.

Conclusions

• The researchers concluded that the high cGPx activity in the RAO-affected horses suggests this redox system (involved in managing oxidative stress) was upregulated, or increased, during exposure to dusty straw and hay. This indicates an attempt to combat oxidative stress as the AA levels were depleted in these horses.
• However, the comparative lack of increase and delay in cGPx activity in the local lung environment (represented by BALF cells) compared to systemic responses (seen in RBCs and WBCs) might be contributing to the disease in these RAO-affected horses.