Nitric oxide and exercise in the horse

Area of Science:

• Equine physiology
• Respiratory and cardiovascular research
• Nitric oxide metabolism

Background:

• Nitric oxide (NO) plays a role in vascular tone regulation.
• Exercise significantly impacts physiological parameters in horses.
• Understanding NO production during exercise is crucial for equine health.

Purpose of the Study:

• To investigate the effects of exercise on nitric oxide (NO) production in exhaled air (VNO) in horses.
• To examine the impact of inhaled NO on cardiovascular and respiratory parameters during exercise.
• To determine the relationship between VNO and exercise intensity, tidal volume, and hematocrit.

Main Methods:

• Measurements of exhaled NO concentration ([NO]) at varying airflow rates during trotting and cantering.
• Administration of nebulized methoxamine to assess its effect on [NO] and breathing patterns.
• Assessment of VNO during graded exercise and immediately post-exercise.
• Inhalation of 80 p.p.m. NO during high-intensity exercise to monitor cardiovascular and respiratory variables.

Main Results:

• Exhaled NO concentration ([NO]) varied with airflow rate and exercise intensity.
• Exercise induced a linear increase in VNO with work intensity, peaking at maximal oxygen uptake and further increasing post-exercise.
• VNO changes correlated significantly with tidal volume and hematocrit.
• Inhaled NO (80 p.p.m.) significantly reduced pulmonary artery pressure during the initial minutes of high-intensity exercise.

Conclusions:

• Exhaled NO is released from equine airways.
• NO production increases with exercise intensity in horses.
• Exhaled NO may contribute to the regulation of pulmonary vascular tone during equine exercise.