The aim of the study was to compare, in a rat model of
congestive heart failure, the effect of
captopril, a selective
angiotensin-converting enzyme (ACE; EC 3.4.15.1) inhibitor, to that of
alatriopril, a mixed inhibitor of ACE and
atriopeptidase (EC 3.4.24.11), an
enzyme implicated in the degradation of
atrial natriuretic factor (
ANF).
Myocardial infarction was induced by
ligation of the left coronary artery. Groups of rats received orally twice daily
captopril (10 mg/kg),
alatriopril (100 mg/kg) or vehicle. Treatments were started 18 to 20 h after
ligation and continued for 4 weeks. Hypertrophic and hormonal changes reflecting
congestive heart failure were assessed in rats with large
infarcts by measuring the relative weight of cardiac tissues as well as by assaying
ANF in heart and plasma and by measuring
renin activity in plasma. Both treatments significantly reduced
cardiac hypertrophy, but
alatriopril showed a greater efficacy than
captopril--the increase in relative heart weight reaching 38% with
captopril and only 22% with
alatriopril (P < .05). The
hypertrophy of right ventricle was reduced by 47% with
alatriopril and by 35% with
captopril (N.S.), whereas the corresponding reductions for atria were 47% vs. 21% (P < .05). Both treatments prevented the
ligation-induced increase of
ANF level in the right ventricle. In contrast, plasma
ANF level was significantly reduced after
captopril but not after
alatriopril treatment, a difference that probably reflects the protection of endogenous
ANF in circulation resulting from
atriopeptidase inhibition. Plasma
renin was increased by 36-fold after
captopril but only by 1.6-fold after
alatriopril, a difference that presumably reflects the inhibition of renal
renin secretion by endogenous
ANF after
alatriopril. These data suggest that enhancement of
ANF levels in circulation via
atriopeptidase inhibition magnifies the capacity of
ACE inhibitors to prevent
cardiac hypertrophy, and they show the potential therapeutic value of mixed ACE-
atriopeptidase inhibitors in
congestive heart failure.