Changes in plasma atrial natriuretic peptide concentration in exercising horses in relation to hydration status and exercise intensity.
OBJECTIVE
To investigate effects of hydration status and exercise intensity on plasma atrial natriuretic peptide (ANP) concentration in exercising horses.


METHODS
4 trained Standardbreds.


METHODS
Horses performed a 40-minute exercise test at 65 to 70% maximal heart rate (HRmax; no incline) and a 12-minute test at approximately 90% HRmax (3.5 degrees incline). The 40-minute test was performed with ad libitum access to drinking water (normohydration), after water had been withheld for 24 hours (dehydration), and 30 minutes after 12 L of water at body temperature had been given via nasogastric tube (hyperhydration). The 12-minute test was only performed with normohydrated horses.


RESULTS
Plasma ANP concentration was higher toward the end of exercise during hyperhydration than during the other 2 hydration states, and the area under the plasma ANP concentration curve was significantly greater during hyperhydration than during dehydration. The maximal plasma ANP value induced during the 12-minute test was similar to that of the 40-minute test. After the 12-minute test, plasma ANP concentration did not decrease during the first 30 minutes of recovery, whereas after the 40-minute test, plasma ANP concentration decreased by approximately 30% during the same period.


CONCLUSIONS
Hydration status can affect plasma ANP concentration in horses during submaximal exercise. Maximal plasma ANP concentration was similar at the 2 exercise intensities studied, but the postexercise return to baseline values differed.


CONCLUSIONS
Changes in hydration status can cause alterations in plasma concentration of ANP, one of the hormones involved in the control of cardiovascular functions during exercise.
Nyman
S
S
Department of Medicine and Surgery, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala.
Kokkonen
U M
UM
Dahlborn
K
K
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000097:blood*; D001798:Blood Proteins / Q000378:metabolism; D005260:Female; D006339:Heart Rate; D006736:Horses / Q000502:physiology*; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D012119:Respiration; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000502:physiology*
D001798:Blood Proteins; D009320:Atrial Natriuretic Factor