Assessment of exercise-induced alterations in neutrophil function in horses.
OBJECTIVE
To evaluate the effects of a standardized exercise test to exhaustion in horses on leukocyte function ex vivo.


METHODS
6 Thoroughbred geldings.


METHODS
Blood samples were obtained from each horse before exercise; at exhaustion (termed failure); and at 2, 6, 24, 48, and 72 hours after exercise to evaluate hematologic changes, rate of leukocyte apoptosis, and leukocyte production of reactive oxygen species (ROS) ex vivo. To assess leukocyte function, leukocyte ROS production in response to stimulation with lipopolysaccharide, peptidoglycan, zymosan, and phorbol myristate acetate was evaluated. Apoptosis was evaluated via assessment of caspase activity in leukocyte lysates.


RESULTS
In response to lipopolysaccharide, production of ROS by leukocytes was significantly increased at 2 hours and remained increased (albeit not significantly) at 6 hours after exercise, compared with the preexercise value. In the absence of any stimulus, leukocyte ROS production was significantly increased at 6 and 24 hours after exercise. In contrast, ROS production in response to phorbol myristate acetate was significantly decreased at 6, 24, and 72 hours after exercise. Leukocyte ROS production induced by zymosan or peptidoglycan was not altered by exercise. Leukocytosis was evident for 24 hours after exercise, and neutrophilia was detected during the first 6 hours. A significant increase in the rate of leukocyte apoptosis was detected at failure and 72 hours after exercise.


CONCLUSIONS
Results indicated that strenuous exercise undertaken by horses causes alterations in innate immune system functions, some of which persist for as long as 72 hours after exercise.
Donovan
Douglas C
DC
Department of Population Health and Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.
Jackson
Christie A
CA
Colahan
Patrick T
PT
Norton
Natalie N
NN
Clapper
Joan L
JL
Moore
James N
JN
Hurley
David J
DJ
D000818:Animals; D017209:Apoptosis / Q000276:immunology; D020169:Caspases / Q000378:metabolism; D006736:Horses / Q000276:immunology* / Q000378:metabolism; D007958:Leukocyte Count / Q000662:veterinary; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D018375:Neutrophil Activation / Q000276:immunology; D009504:Neutrophils / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D010457:Peptidoglycan / Q000494:pharmacology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000276:immunology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015054:Zymosan / Q000276:immunology / Q000494:pharmacology
D008070:Lipopolysaccharides; D010457:Peptidoglycan; D017382:Reactive Oxygen Species; D015054:Zymosan; D020169:Caspases; D013755:Tetradecanoylphorbol Acetate