Imidapril,
enalapril and
quinapril were subcutaneously administered to aortic-banded rats by osmotic minipumps to compare the suppressive actions of these
angiotensin converting enzyme (
ACE) inhibitors on pressure-induced
cardiac hypertrophy. Among the three drugs tested,
imidapril was most potent for the prevention of
cardiac hypertrophy, although equipotent hypotensive doses were used.
Imidapril reduced both serum and cardiac ACE activities, while
enalapril reduced only the former.
Quinapril also reduced both, however, it was less potent at reducing the former compared to
imidapril. Moreover, only
imidapril significantly decreased left ventricular end diastolic pressure, which tended to be increased by aortic-banding. The lipophilicity of
ACE inhibitors could not explain the more potent suppressive action of
imidapril on
cardiac hypertrophy because the lipophilicity of
imidaprilat, an active metabolite of
imidapril, was as low as an active metabolite of
enalapril; i.e., much lower than an active metabolite of
quinapril. The efficacy of
ACE inhibitors on pressure-induced
cardiac hypertrophy depends not only on an inhibitory effect on cardiac ACE activity, but also on other actions such as their effect on left ventricular end diastolic pressure.