Reasons for performing study: There is limited understanding of the uric acid response to endurance races.
Objectives: To demonstrate uric acid increments and its relationship to diverse biochemical and performance parameters, in horses subjected to a prolonged effort, with and without presentation of metabolic alterations.
Methods: Blood samples were taken from horses the day before, and 5-10 mins after, successfully finishing a 121 km (Assay 1, n = 24) or 164 km endurance race (Assay 2, n = 17), and from 19 animals eliminated by metabolic disorders during several endurance races (Assay 3). Plasma was obtained and determinations of CK, AST, LDH, AP, uric acid (UA), creatinine (Cr), urea, lactate (La) and plasma proteins (PP) carried out. Sex, age, time in competition, average speed and total recovery time were also recorded. Assays 1 and 2 were arithmetically subdivided into 3 groups each in order to categorise time in competition, average speed and total recovery time. Changes among the groups were evaluated with ANOVA and Fisher's PLSD test. Student's paired t test was used to assess pre- and post exercise differences. A value of P< or =0.05 was considered significantly different. Pearson correlation coefficient was used to assess the relationship between all the variables and UA increases.
Results: Average speed of the sampled horses was significantly higher in Assay 1 compared to Assay 2. However, there were no significant differences in plasma biochemistry values between both groups. The fastest horses showed significantly higher UA levels, compared with the slowest (Assays 1 and 2) and medium horses (Assay 1). The animals with alterations in metabolism had significantly higher UA, CK and PP compared with those that adequately concluded the race. There were significant correlations between UA and CK in Assays 1, 2, and 3 and between UA and PP in Assays 1 and 3.
Conclusions: UA rises in horses after a prolonged effort, this increase being higher in animals with metabolic commitment, and in the fastest horses. This increase has a direct correlation with CK.
Potential relevance: UA could be useful in the assessment of metabolic response during endurance exercise.