Effects of chronic acetazolamide administration on gas exchange and acid-base control in pulmonary circulation in exercising horses.

The study observed the effects of inhibiting the enzyme carbonic anhydrase in exercising horses. The findings suggested that this inhibition could lead to a reduction in carbon dioxide output, imbalance in acid-base and ions on pulmonary circulation during exercise.

Research Purpose

• The intent of the study was to understand the effects of inhibiting the enzyme Carbonic anhydrase (CA) on the acid-base balance and the carbon dioxide (CO2) output in horses during exercise.
• Specifically, the researchers were interested in observations around ionic exchange between erythrocytes and plasma in the pulmonary vessels (lung vessels), both with and without CA inhibition.

Methods and Process

• Six horses were made to exercise to exhaustion on a treadmill, with and without CA inhibition, named as AczTr and Con respectively.
• To achieve CA inhibition, acetazolamide was administered to the horses (10 mg/kg body weight thrice a day for 3 days and 30 mg/kg body weight before exercise).
• Arterial, mixed venous blood and CO2 output were sampled at rest and during exercise. A physicochemical systems approach was employed to describe the acid-base changes.

Findings

• The exercising duration decreased by 45% when CA was inhibited. Also, the CO2 output during the shift from rest to exercise was less for the horses with CA inhibition.
• The horses treated with acetazolamide showed higher arterial PCO2 but lower hydrogen ion and bicarbonate differences across the lung when compared to the control group.
• There were no observed differences in weak electrolytes across the lung in either group.
• The strong ion difference across the lung was lesser in the treated group, impacted by changes in strong ion across the lung barring lactate.

Conclusions

• The researchers concluded that changes in CO2 and chloride in erythrocytes across the lung play a critical role in maintaining the acid-base and ions balance in the pulmonary circulation in exercising horses.

The significant observation of this research is the impact of CA inhibition on the acid-base balance in horses, potentially affecting their performance during exercise, hinting at the influence of CA on the physiological processes involved.