ACCUMULATION OF URIC-ACID IN PLASMA AFTER REPEATED BOUTS OF EXERCISE IN THE HORSE

Plasma concentration of uric acid, total peroxyl radical-trapping anti oxidative parameter (TRAP), blood lactate concentration and plasma act ivity of xanthine oxidase (XO) were measured in six Standardbreed trot ters after six bouts of exercise with increasing intensity on two sepa rate days three days apart. Blood samples were taken immediately, 5, 1 0, 15, 30 and 60 min after each heat and 2, 4, and 6 hr after the last heat. Exercise caused an increase in TRAP and in the concentrations o f lactate and uric acid. Plasma uric acid concentration increased expo nentially with respect to time after the last heat performed at maxima l speed, indicating a rapid increase in the rate of purine degradation . Plasma XO activity increased during exercise, but the intensity of e xercise had only a minor effect on the level of XO activity. In conclu sion, these data suggest that a threshold for the plasma accumulation of uric acid in terms of the intensity of exercise may exist and that XQ may play a role in the formation of uric acid in horse plasma. Inte nse exercise causes an increase in the plasma antioxidant capacity tha t in the horse is mainly caused by the increase in the plasma uric aci d concentration.