Intravenous infusion of H(2)-saline suppresses oxidative stress and elevates antioxidant potential in Thoroughbred horses after racing exercise

Upon intensive, exhaustive exercise, exercise-induced reactive oxygen species may exceed the antioxidant defence threshold, consequently resulting in muscular damage or late-onset chronic inflammation. Recently, the therapeutic antioxidant and anti-inflammatory effects of molecular hydrogen (H(2)) for human rheumatoid arthritis have been demonstrated. However, it is also important to clarify the effects of administrating H(2) in large animals other than humans, as H(2) is thought to reach the target organ by passive diffusion upon delivery from the blood flow, indicating that the distance from the administration point to the target is critical. However, data on the effects of H(2) on oxidative stress in real-life exhaustive exercise in large animals are currently lacking. We here investigated 13 Thoroughbred horses administered intravenous 2-L saline with or without 0.6-ppm H(2) (placebo, N = 6; H(2), N = 7) before participating in a high-intensity simulation race. Intravenous H(2)-saline significantly suppressed oxidative stress immediately, 3 h, and 24 h after the race, although the antioxidant capability was not affected throughout the study. The serum creatine kinase, lactate, and uric acid levels were increased in both groups. Taken together, these results indicate that intravenous H(2)-saline can significantly and specifically suppress oxidative stress induced after exhaustive racing in Thoroughbred horses.