Effects of enalaprilat on cardiorespiratory, hemodynamic, and hematologic variables in exercising horses.

The study tested the effects of enalaprilat (a medication used to treat hypertension) on the heart and breathing rates, blood flow, and blood variables in exercising horses, concluding that while enalaprilat greatly limited angiotensin converting enzyme (ACE) activity, it didn’t noticeably change the horses’ cardiorespiratory responses or prevent exercise-induced pulmonary bleeding.

Research Background

• The study was performed to understand whether the intravenous administration of enalaprilat has any significant effects on cardiorespiratory, hemodynamic (blood flow-related), and hematologic (blood-related) variables in horses that have been exercising.
• It also sought to study the extent of inhibition of angiotensin converting enzyme (ACE) activity by enalaprilat.

Research Methodology

• Six adult horses were chosen and trained on a treadmill for five weeks. The training continued throughout the study period and each horse ran two simulated races at 120% of their maximum oxygen consumption.
• Three horses were randomly chosen for treatment one (administration of saline solution), and the other three were chosen for treatment two (administration of enalaprilat).
• The treatment groups were then swapped for the second simulated race.
• Data regarding cardiorespiratory and hematologic measures were gathered before, during, and one hour after the simulated races.
• The level of ACE activity inhibition was determined during and after each race for all the horses.

Research Findings

• All hemodynamic variables and the rate of respiration significantly increased due to exercise.
• The pH and PO2 level of arterial blood decreased during the simulated races while the PCO2 remained unchanged.
• However, these values returned to their baseline 60 minutes after the races.
• Enalaprilat significantly inhibited ACE activity, to below 25% of the baseline activity, though it held no evident impact on cardiorespiratory or blood gas values when compared to horses given saline solution.

Research Conclusion

• The administration of enalaprilat led to extreme inhibition of ACE activity in horses.
• However, it did not alter the hemodynamic responses to high-intensity exercise, therefore, it is not expected to be effective in preventing exercise-induced pulmonary hemorrhage in horses.