Effects of acetazolamide on metabolic and respiratory responses to exercise at maximal O2 uptake.

This research investigates the effects of acetazolamide, a medication typically used for altitude sickness, on the metabolic and respiratory responses during strenuous exercise in horses. The findings suggest that acetazolamide induces higher levels of acidosis and CO2 retention in the horses during exercise, potentially impairing their exercise capacity and muscle metabolism.

Overview of study and methodologies

• The study used both normal horses and horses treated with acetazolamide, a medication typically used to prevent and reduce symptoms of altitude sickness. The goal of the experiment was to test whether acetazolamide-induced acidosis would impact the metabolism of horses exercising at their maximum oxygen uptake. This was tested by measuring a variety of parameters including blood gases, ions, lactate, pH, hemoglobin, blood temperature, total body metabolism, and muscle metabolites in the horses both before and during exercise, as well as during recovery.

Main findings

• The findings demonstrated that acetazolamide-treated horses exhibited a base deficit at rest and higher arterial oxygen pressure both at rest and during exercise. They also exhibited higher arterial and mixed venous carbon dioxide pressure during exercise.
• This treatment resulted in a 48-second reduction in run time, suggesting that the medication negatively affected exercise performance.
• While arterial pH was found to be lower during exercise for the acetazolamide-treated horses, this did not persist during recovery. The normal body temperature responses were not affected by the administration of acetazolamide.
• Following acetazolamide treatment, the oxygen uptake was found to be the same during exercise and recovery as it was before the treatment. However, carbon dioxide production was lower during exercise post-treatment.
• Finally, after acetazolamide treatment, certain biochemical markers in the muscle were lower at rest, while heart rate, muscle pH, muscle lactate concentration, plasma lactate concentration and potassium concentration were also lower after exercise. Plasma chloride concentration, on the other hand, was increased following exercise.

Final conclusions

• The collective data showed that the administration of acetazolamide resulted in increased CO2 retention and acidosis in horses during strenuous exercise. The study concluded that these conditions might negatively affect muscle metabolism and the overall capacity for exercise in these horses.

These findings could have implications for the use of acetazolamide in athletic horses, particularly those that train in high altitude environments where the medication may be used as a prophylactic for altitude sickness.