Changes in plasma atrial natriuretic peptide concentration in exercising horses in relation to hydration status and exercise intensity.

This research paper examines the effects of different levels of hydration and intensity of exercise on the concentration of atrial natriuretic peptide (ANP), a hormone related to heart function, in the blood of exercising horses.

Methodology

• The researchers ran tests on 4 trained Standardbred horses, specifically focusing on exercise intensity relative to maximum heart rate (HRmax) and three states of hydration: normohydration (regular access to water), dehydration (water withheld for 24 hours), and hyperhydration (given additional water via a nasogastric tube).
• Two different exercise tests were performed: a 40-minute exercise at 65 to 70% HRmax without incline, and a 12-minute test at approximately 90% HRmax with a 3.5-degree incline. The 40-minute test was performed under all three hydration conditions, while the 12-minute test was performed exclusively with normohydrated horses.

Results

• Plasma ANP concentration was found to increase towards the end of the exercise during hyperhydration compared to the other hydration states.
• After 12-minutes of high-intensity exercise, the plasma ANP concentration did not decrease during the first 30 minutes of recovery. In contrast, there was a 30% decrease in ANP concentration during the same recovery period following 40-minutes of moderate exercise.
• The maximal plasma ANP value recorded during the 12-minute test was similar to that of the 40-minute test.

Conclusions

• The study concluded that the hydration status can affect the plasma ANP concentration in horses during submaximal exercise.
• Also, it found that the maximum plasma ANP concentrations were similar at both exercise intensities studied, but the post-exercise return to baseline values differed based on exercise duration and intensity.
• These findings suggest that changes in hydration status can cause alterations in plasma concentration of ANP, an important hormone in controlling cardiovascular functions during exercise.