Pulmonary epithelial lining fluid and plasma ascorbic acid concentrations in horses affected by recurrent airway obstruction.
OBJECTIVE
To determine the pulmonary epithelial lining fluid (ELF) concentrations and degree of oxidation of ascorbic acid in horses affected by recurrent airway obstruction (RAO) in the presence and absence of neutrophilic airway inflammation.


METHODS
6 RAO-affected horses and 8 healthy control horses.


METHODS
Nonenzymatic antioxidant concentrations were determined in RBC, plasma, and ELF samples of control horses and RAO-affected horses in the presence and absence of airway inflammation.


RESULTS
ELF ascorbic acid concentration was decreased in RAO-affected horses with airway inflammation (median, 0.06 mmol/L; 25th and 75th percentiles, 0.0 and 0.4 mmol/L), compared with RAO-affected horses without airway inflammation (1.0 mmol/L; 0.7 and 1.5 mmol/L) and control horses (2.2 mmol/L; 1.4 and 2.2 mmol/L). Epithelial lining fluid ascorbic acid remained significantly lower in RAO-affected horses without airway inflammation than in control horses. Moreover, the ELF ascorbic acid redox ratio (ie, ratio of the concentrations of dehydroascorbate to total ascorbic acid) was higher in RAO-affected horses with airway inflammation (median, 0.85; 25th and 75th percentiles, 0.25 and 1.00), compared with RAO-affected horses without airway inflammation (0.04; 0.02 and 0.22). The number of neutrophils in bronchoalveolar lavage fluid was inversely related to the ELF ascorbic acid concentration (r = -0.81) and positively correlated with the ascorbic acid redox ratio (r = 0.65).


CONCLUSIONS
Neutrophilic inflammation in horses affected by RAO is associated with a reduction in the ELF ascorbic acid pool. Nutritional supplementation with ascorbic acid derivatives in horses affected by RAO is an area for further investigation.
Deaton
Christopher M
CM
Centre for Equine Studies, Animal Health Trust, Lanwades Park, Kentford, Suffolk, CB8 7UU, UK.
Marlin
David J
DJ
Smith
Nicola C
NC
Harris
Pat A
PA
Roberts
Colin A
CA
Schroter
Robert C
RC
Kelly
Frank J
FJ
D000818:Animals; D000975:Antioxidants / Q000032:analysis; D001205:Ascorbic Acid / Q000032:analysis* / Q000097:blood; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry*; D004848:Epithelium / Q000503:physiopathology; D006734:Horse Diseases / Q000097:blood / Q000503:physiopathology*; D006736:Horses; D008168:Lung / Q000503:physiopathology*; D008173:Lung Diseases, Obstructive / Q000097:blood / Q000503:physiopathology / Q000662:veterinary*; D011014:Pneumonia / Q000503:physiopathology / Q000662:veterinary
D000975:Antioxidants; D001205:Ascorbic Acid