Arterial-venous difference in atrial natriuretic peptide concentration during exercise in horses.

This research paper investigates how exercise influences the concentration of a hormone called atrial natriuretic peptide (ANP) in horses’ blood. Both arterial and venous blood were tested in this study.

Experiment Design

• The research involved six untrained mares who were subjected to a steady-state, submaximal treadmill exercise. This ensured that the circumstances remained the same across all subjects.
• The exercise required was calculated to expend around 80% of the maximum oxygen uptake, or VO2MAX. This is a consistent and precise measure to assess the intensity of exercise.
• The horses were made to run on a treadmill at a 6-degree gradient for a sustained period of 20 minutes.

Data Collection

• Simultaneous arterial and venous blood samples were taken from the carotid and pulmonary arteries of the horses at rest, and then at 10 minute intervals during the 20-minute exercise.
• The blood plasma was stored at -80 degrees Celsius soon after collection to prevent deterioration and was later thawed for ANP extraction and measurement.
• The concentration of ANP was determined using a method called radioimmunoassay, a sensitive assessment technique used to measure the concentration of hormones in the blood.

Results and Interpretation

• Exercise was found to significantly increase both arterial and venous plasma ANP concentrations (P < 0.05). P < 0.05 indicates a statistically significant result, suggesting that the changes observed are unlikely due to random variation.
• The arterial ANP concentration increased from an average of 25.2pg/ml at rest to 52.7pg/ml at 10 minutes of exercise and 62.5pg/ml at 20 minutes of exercise.
• The venous ANP concentration increased from an average of 24.8pg/ml at rest to 67.2pg/ml at 10 minutes of exercise and 65.3pg/ml at 20 minutes of exercise.
• No significant differences were observed between arterial and venous ANP concentration at rest or during exercise. This may suggest that ANP is either not metabolized in the lungs, or is released from the left atrium at a rate that matches pulmonary metabolism.