Concurrent neutral endopeptidase and ACE inhibition in experimental heart failure: renal and hormonal effects

Beneficial renal and cardiac effects of vasopeptidase inhibition with S21402 in heart failure

S21402 is a vasopeptidase inhibitor that simultaneously inhibits neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE). This study determined whether chronic treatment with S21402 produced different effects on sodium and water excretion, hormonal parameters, and cardiovascular structure compared with selective inhibition of ACE and NEP in a rat model of myocardial infarction-induced congestive heart failure (CHF). CHF rats received the vasopeptidase inhibitor (S21402, 100 mg. kg(-1). d(-1)), an ACE inhibitor (captopril, 50 mg. kg(-1). d(-1)), a NEP inhibitor (SCH42495, 60 mg. kg(-1). d(-1)), or vehicle for 4 weeks. S21402 alone caused a diuresis and natriuresis (P<0.01) in CHF. After 4 weeks, blood pressure was lowered by captopril but not other treatments (P<0.01). Both S21402 and captopril increased plasma renin activity (P<0.01), all treatment lowered plasma aldosterone (P<0.05) and plasma natriuretic peptide levels were unchanged. In the kidney, S21402 inhibited NEP and ACE (P<0.01), SCH42495 inhibited NEP (P<0.01), and captopril inhibited ACE (P<0.01). Heart mass was reduced by all active treatments; captopril reduced left ventricular mass (P<0.01), SCH42495 reduced right ventricular mass (P<0.01), and S21402 decreased left (P<0.05) and right ventricular mass (P<0.01), atrial mass (P<0.05), and lung mass (P<0.01). In CHF, vasopeptidase inhibition with S21402 produces effects that differ from those of selective NEP or ACE inhibition. S21402 improved sodium and water excretion, reduced pulmonary congestion, and attenuated both right and left ventricular remodeling. These effects, which occurred in the absence of any hypotensive action, suggest that S21402 may offer several advantages over ACE inhibition alone in the treatment of heart failure.

Renal effects of concurrent E-24.11 and ACE inhibition in the aorto-venocaval fistula rat

1. The present studies compare the early renal response to (a) an endopeptidase-24.11 (E-24.11) inhibitor (candoxatrilat) (b) an angiotensin-converting enzyme (ACE) inhibitor (lisinopril) and (c) the combination of endopeptidase-24.11 and ACE inhibition in the rat A-V fistula model of chronic volume overload. 2. Candoxatrilat (3 and 10 mg kg-1) i.v. produced a prompt 3 fold increase in urinary sodium and cyclic GMP excretion without affecting significantly blood pressure or glomerular filtration rate (GFR). 3. Lisinopril (0.03 mg kg-1) alone inhibited the pressor response to angiotensin I but had no significant effect on urinary sodium excretion or blood pressure. 4. Lisinopril (0.03 mg kg-1) attenuated significantly the early natriuretic response to candoxatrilat (3 mg kg-1) and the associated rise in urinary cyclic GMP, but sodium excretion eventually reached levels associated with acute E-24.11 inhibition. 5. Doses of the dual E-24.11/ACE inhibitor, sampatrilat, that inhibited the pressor response to angiotensin I reduced mean arterial blood pressure and produced a delayed natriuresis and rise in urinary cyclic GMP excretion when compared to candoxatrilat alone. 6. Concurrent administration of an ACE inhibitor reduces the early renal response to E-24.11 inhibition in the A-V fistula rat, an effect attributable to the hypotensive action of this combination.

Inhibition of either angiotensin-converting enzyme or neutral endopeptidase induces both enzymes

Synthesis of angiotensin-converting enzyme is induced during its chronic inhibition. Like angiotensin-converting enzyme, neutral endopeptidase (EC 3.4.24.11) is a plasma membrane peptidase. We studied changes of the two enzymes in lung, kidney and serum in a coronary ligation model of experimental congestive heart failure, and during chronic inhibition of the enzymes. Coronary-ligated rats (n = 19) and sham-operated controls (n = 18) were given SCH 34826 [(S)-N-[N-[1-[[(2,2-dimethyl-1,3-dioxolan-4-yl) methoxy]carbonyl]-2-phenylethyl]-L-phenylalanine]-beta-alanine], a specific neutral endopeptidase inhibitor (n = 13), captopril (n = 12), or vehicle (n = 12) for 4 days, and exsanguinated. Pulmonary angiotensin-converting enzyme was induced both by captopril (52% compared to vehicle) and by SCH 34826 (21%). Serum angiotensin-converting enzyme was induced by captopril (44%). Neutral endopeptidase was induced in lung by captopril (73%), and in kidney by SCH 38426 (32%). Compared to controls, the relative heart weight of rats with heart failure was increased by 29%, and the plasma level of atrial natriuretic peptide elevated by 74%, but enzyme activities were not different. We conclude that, in the rat, separate inhibition of either angiotensin-converting enzyme or neutral endopeptidase induces both enzymes, and that the induction varies in different tissues. Alterations in the substrates of the two enzymes, e.g. in bradykinin, might cause these changes.