Plasma atrial natriuretic peptide in standardbred and Finnhorse trotters during and after exercise.

This research observes the changes in the production of a hormone called atrial natriuretic peptide (ANP) in two breeds of trotting horses (Standardbred and Finnhorse) during and after exercise. The study found that the hormone levels increased significantly in both types of horses during intense exercise, with higher heart rates explaining about 40% of the variations in the presence of the hormone in the horses’ plasma.

Exercise Test and Heart Rate Observations

• The study was carried out using an incremental submaximal exercise test on a high-speed treadmill with two breeds of trotting horses: Standardbred and Finnhorse.
• The horses performed 2-minute exercise intervals at varying speeds, depending on their breed and training status. Standardbred horses ran at speeds between 6 m/s and 9 m/s, while Finnhorses ran at speeds between 5m/s and 8m/s or 4m/s and 7m/s.
• It was observed that a steady-state heart rate was achieved within each 2-minute interval. The increase in heart rate was found to be linear and proportional to the intensity of the work and the physical condition of the horse, peaking at an average of 204 beats per minute during the last speed of the treadmill.

ANP Response to Exercise

• Atrial natriuretic peptide (ANP) is a hormone with cardiovascular and renal effects. The research aimed to study changes in this hormone in response to exercise.
• It was found that plasma ANP increased significantly in both breeds of horses during exercise, by an average of 27 pg/mL. This increase peaked 5 minutes after the exercise ended.
• The rise in ANP during exercise showed good linearity with increased heart rate and work intensity, meaning that as the horse’s heart rate and intensity of work increased, so did their ANP levels.

Atrial Natriuretic Peptide (ANP) Role and After-Exercise Observations

• The decrease in ANP levels was slow post-exercise, which the study suggests might be related to the regulation of water and electrolytes in the horses’ bodies.
• No differences were found in ANP levels between the two breeds of horses, indicating that breed may not significantly affect this hormone’s response to exercise.
• The study suggests that the ANP hormone may play a role in cardiovascular control and fluid balance during and after exercise. The increase in heart rate during exercise explained about 40% of the variability in plasma ANP levels.