Renin-Angiotensin-Aldosterone System Profiling in Horses Before and After Exercise.
Authors: Holbrook Todd, Hernandez Jorge, McCarrel Taralyn, Lester Guy, Sleeper Margaret, Domenig Oliver, Adin Darcy
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: RAAS Activation in Exercised Horses Exercise triggers activation of both the classical and alternative renin-angiotensin-aldosterone system (RAAS) pathways in horses, according to new research profiling 25 animals across four distinct exercise modalities ranging from endurance rides to sprints. Researchers measured serum RAAS metabolites and enzyme activity before and after exercise in Arabians completing a 50-mile endurance ride, Thoroughbreds on a treadmill or racing 1–1⁄16 miles, and Quarter Horses racing 330–500 yards, finding substantial increases across all measured variables: angiotensin II concentrations rose more than fivefold (10.2 to 53.0 pmol/L), aldosterone approximately doubled (83.8 to 170.6 pmol/L), and the alternative pathway metabolite angiotensin 1–7 increased threefold (1.5 to 5.1 pmol/L). Notably, short-duration, high-intensity sprinting generated disproportionately high angiotensin 1–7 ratios compared with endurance or treadmill exercise, suggesting the alternative pathway's relative contribution varies by exercise intensity rather than duration alone. Clinicians should recognise that RAAS profiling may offer insights into individual stress responses and cardiovascular adaptation, potentially informing conditioning protocols, monitoring of performance horses under physiological stress, and management of conditions involving dysregulated fluid and electrolyte balance.
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Practical Takeaways
- •Both RAAS pathways activate during equine exercise; understanding this may inform management of post-exercise recovery, particularly for endurance and high-performance horses
- •High-intensity, short-duration exercise produces a different neurohormonal profile than endurance exercise, suggesting training type may influence cardiovascular and fluid-electrolyte responses
- •Monitoring RAAS activation could become relevant for assessing recovery adequacy and stress levels in competition horses, though clinical application remains to be established
Key Findings
- •Exercise significantly increased classical RAAS metabolites: angiotensin I increased from 2.5 to 8.2 pmol/L, angiotensin II from 10.2 to 53.0 pmol/L, and aldosterone from 83.8 to 170.6 pmol/L (p<0.001)
- •Alternative RAAS pathway also activated with angiotensin 1-7 increasing from 1.5 to 5.1 pmol/L and angiotensin 1-5 from 2.5 to 14.9 pmol/L (p<0.001)
- •Angiotensin-converting enzyme-2 activity increased from 16.6 to 25.2 ng/mL post-exercise (p<0.001)
- •Short-duration, high-intensity exercise (1-mile race) produced higher angiotensin 1-7 ratios compared to endurance and treadmill exercise, contrary to initial hypothesis