Effect of the ACE inhibitor enalapril on plasma ACE concentration in horses with left side heart valve insufficiency

Abstract

Even though angiotensin-converting enzyme (ACE) inhibitors are often used in horses, only a few studies exist that investigate the effect of these drugs in horses suffering from heart disease. The aim of this work was to examine the effect of the ACE inhibitor enalapril on the plasma ACE concentration of horses diagnosed with a left-sided heart valve insufficiency. We hypothesize that the use of the ACE inhibitor enalapril leads to a lowered ACE concentration in the equine blood plasma of horses suffering from a left-side heart valve insufficiency. Therefor we evaluated twenty-five horses with aortic and/or mitral valve insufficiency. All animals received daily dose of enalapril per os (0.5 mg/ kg) over a period of three months. The horses were divided into two groups. Horses in Group 1 were examined immediately prior to the trials and after the three-month therapy period. Horses in Group 2 were examined a third time, three months prior to the start of treatment with enalapril. Serum ACE concentration was measured photometrically. No horse showed any signs of noticeable adverse effects. A statistically significant increase in ACE activity has been recorded in Group 1 and Group 2 under the therapy with enalapril (p = 0.00). While no treatment was performed on the horses in Group 2, no statistically significant difference in ACE activity could be shown (p = 0.00). The study showed an effect of the ACE inhibitor enalapril on the renin-angiotensin-aldosterone system in horses diagnosed with left-side heart valve insufficiency. However, our results contradicted expectations that enalapril would lead to a lowered ACE concentration in the equine blood plasma. Further studies on cardiac efficacy would be desirable.