Physical exertion is a stimulus for the upregulation of cytokine production including IL-1β, IL-1ra, IL-2, IL-4, IL-6, IL-10 and TNF-α in horses. To investigate that hypothesis, we initiated training of 5 stall-rested Thoroughbreds. Blood samples were drawn before and weekly during training. The relative transcription of mRNA within the leucocytes was measured using real time TaqMan quantitative PCR.
The training protocol was walking (3 min), trotting (3 min) and cantering/galloping (6 min) increasing in intensity weekly (6 to 12 m/s) and culminating in an intense exercise period. Comparisons of mRNA concentrations were made using a repeated measures ANOVA on ranks and a Student-Newman-Keuls pair-wise multiple comparison (P<0.05).
The training programme or intense exercise bout did not affect IL-2, IL-4, IL-6 and IL-10. IL1-β and TNF-α transcription increased on Day 23. TNF-α peaked on Day 23 and IL1-β on Day 30. Neither demonstrated a response to intense exercise. IL-1ra decreased significantly on Day 9; rose significantly from Day 9 to Days 16 and 23; remained significantly elevated through Days 30 and 37 over Day 9, and rose very slightly after intense exercise on Day 56.
Alterations in leukocyte cytokine responses may influence susceptibility to infectious disease, metabolic responses to exercise or exercised induced syndromes.