Body Temperature and Plasma Nitric Oxide Metabolites in Response to Standardized Exercise Test in the Athletic Horse

The present study was undertaken to examine the relationship among the circulating levels of nitric oxide metabolites (NOx) and gas parameters and body temperature in horses before and after a standardized exercise test (SET). Total levels of NOx were calculated as the sum of nitrite (NO3-) and nitrate (NO2-) levels. The results indicate that blood gas parameters were significantly modified at short time after SET (5 minutes), normalizing at 30 minutes after SET. A significant increase of body temperature (P < .001) and plasma NOx levels (P < .05) was observed at both 5 and 30 minutes after SET. A linear correlation between the postexercise values of NOx and body temperature (r(2) = 0.501, P < .01) was found. According to these data, plasma NOx could be involved in thermoregulation during physical exercise in horses; further studies are necessary to investigate this association and to understand the systems that permit animals to maintain homeostasis during body exercise.