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Bozkurt B, Nair AP, Misra A, Scott CZ, Mahar JH, Fedson S. Neprilysin Inhibitors in Heart Failure: The Science, Mechanism of Action, Clinical Studies, and Unanswered Questions. JACC. BASIC TO TRANSLATIONAL SCIENCE 2022; 8:88-105. [PMID: 36777165 PMCID: PMC9911324 DOI: 10.1016/j.jacbts.2022.05.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 05/18/2022] [Accepted: 05/18/2022] [Indexed: 11/16/2022]
Abstract
This article provides a contemporary review and a new perspective on the role of neprilysin inhibition in heart failure (HF) in the context of recent clinical trials and addresses potential mechanisms and unanswered questions in certain HF patient populations. Neprilysin is an endopeptidase that cleaves a variety of peptides such as natriuretic peptides, bradykinin, adrenomedullin, substance P, angiotensin I and II, and endothelin. It has a broad role in cardiovascular, renal, pulmonary, gastrointestinal, endocrine, and neurologic functions. The combined angiotensin receptor and neprilysin inhibitor (ARNi) has been developed with an intent to increase vasodilatory natriuretic peptides and prevent counterregulatory activation of the angiotensin system. ARNi therapy is very effective in reducing the risks of death and hospitalization for HF in patients with HF and New York Heart Association functional class II to III symptoms, but studies failed to show any benefits with ARNi when compared with angiotensin-converting enzyme inhibitors or angiotensin receptor blocker in patients with advanced HF with reduced ejection fraction or in patients following myocardial infarction with left ventricular dysfunction but without HF. These raise the questions about whether the enzymatic breakdown of natriuretic peptides may not be a very effective solution in advanced HF patients when there is downstream blunting of the response to natriuretic peptides or among post-myocardial infarction patients in the absence of HF when there may not be a need for increased natriuretic peptide availability. Furthermore, there is a need for additional studies to determine the long-term effects of ARNi on albuminuria, obesity, glycemic control and lipid profile, blood pressure, and cognitive function in patients with HF.
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Key Words
- ACE, angiotensin-converting enzyme
- ANP, atrial natriuretic peptide
- ARB, angiotensin receptor blocker
- ARN, angiotensin receptor–neprilysin
- ARNi
- Aβ, amyloid beta
- BNP, brain natriuretic peptide
- BP, blood pressure
- CSF, cerebrospinal fluid
- EF, ejection fraction
- FDA, U.S. Food and Drug Administration
- GFR, glomerular filtration rate
- HF, heart failure
- HFpEF, heart failure with preserved ejection fraction
- HFrEF, heart failure with reduced ejection fraction
- LV, left ventricular
- LVEF, left ventricular ejection fraction
- MI, myocardial infarction
- NEP inhibitor
- NT-proBNP, N-terminal pro–brain natriuretic peptide
- NYHA, New York Heart Association
- PDE, phosphodiesterase
- RAAS, renin-angiotensin-aldosterone system
- UACR, urinary albumin/creatine ratio
- angiotensin receptor–neprilysin inhibitor
- cGMP, cyclic guanosine monophosphate
- eGFR, estimated glomerular filtration rate
- heart failure
- neprilysin
- neprilysin inhibitor
- sacubitril
- sacubitril/valsartan
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Affiliation(s)
- Biykem Bozkurt
- Winters Center for Heart Failure Research, Cardiovascular Research Institute, Baylor College of Medicine, DeBakey Veterans Affairs Medical Center, Houston Texas, USA
- Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
- Michael E. DeBakey Veterans Affairs Medical Center, Houston Texas, USA
- Address for correspondence: Dr Biykem Bozkurt, MEDVAMC, 2002 Holcombe Boulevard, Houston, Texas, 77030, USA.
| | - Ajith P. Nair
- Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Arunima Misra
- Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
- Michael E. DeBakey Veterans Affairs Medical Center, Houston Texas, USA
| | - Claire Z. Scott
- Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Jamal H. Mahar
- Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Savitri Fedson
- Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
- Michael E. DeBakey Veterans Affairs Medical Center, Houston Texas, USA
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Maurer MS, Packer M. Impaired systemic venous capacitance: the neglected mechanism in patients with heart failure and a preserved ejection fraction? Eur J Heart Fail 2020; 22:173-176. [DOI: 10.1002/ejhf.1702] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Revised: 10/20/2019] [Accepted: 11/08/2019] [Indexed: 01/07/2023] Open
Affiliation(s)
| | - Milton Packer
- Baylor Heart and Vascular InstituteBaylor University Medical Center Dallas TX USA
- Imperial College London London UK
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Khder Y, Shi V, McMurray JJV, Lefkowitz MP. Sacubitril/Valsartan (LCZ696) in Heart Failure. Handb Exp Pharmacol 2017; 243:133-165. [PMID: 28004291 DOI: 10.1007/164_2016_77] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
It has been known since the 1990s that long-term morbidity and mortality is improved in patients with heart failure with reduced ejection fraction (HFrEF) by treatments that target the renin-angiotensin-aldosterone system (RAAS). It has also long been thought that enhancement of the activity of natriuretic peptides (NPs) could potentially benefit patients with HFrEF, but multiple attempts to realize this benefit had failed over the years - until 2014, when a large, phase III, randomized, controlled clinical trial (PARADIGM-HF) was completed comparing sacubitril/valsartan with enalapril, a well-established treatment for HFrEF. Sacubitril/valsartan (formerly known as LCZ696) is a first-in-class angiotensin receptor neprilysin inhibitor (ARNI) that simultaneously suppresses RAAS activation through blockade of angiotensin II type 1 receptors and enhances vasoactive peptides including NPs through inhibition of neprilysin, the enzyme responsible for their degradation. In PARADIGM-HF, patients with HFrEF treated with sacubitril/valsartan had 20% less risk for cardiovascular death or hospitalization for heart failure (the primary endpoint), 20% less risk for cardiovascular death, 21% less risk for first hospitalization for heart failure, and 16% less risk for death from any cause, compared with enalapril (all p < 0.001). Concerning tolerability, the sacubitril/valsartan group had higher proportions of patients with hypotension and nonserious angioedema but lower proportions with renal impairment, hyperkalemia, and cough, compared with the enalapril group. The use of sacubitril/valsartan has been endorsed by the latest heart failure treatment guidelines in Europe and the USA. This chapter reviews the discoveries, scientific reasoning, and clinical evidence that led to the development of sacubitril/valsartan, the first novel therapy in a new drug class to improve survival in HFrEF in the last 15 years.
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Affiliation(s)
- Yasser Khder
- Novartis Institutes for Biomedical Research, Postfach, 4002, Basel, Switzerland.
| | - Victor Shi
- Novartis Pharmaceuticals Corporation, One Health Plaza, East Hanover, NJ, 07936-1080, USA
| | - John J V McMurray
- British Heart Foundation Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Martin P Lefkowitz
- Novartis Pharmaceuticals Corporation, One Health Plaza, East Hanover, NJ, 07936-1080, USA
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Chee KH, Amudha K, Hussain NA, Haizal HK, Choy AMJ, Lang CC. Combination of drugs acting on the natriuretic system and the renin-angiotensin system in heart failure. J Renin Angiotensin Aldosterone Syst 2016; 4:140-8. [PMID: 14608517 DOI: 10.3317/jraas.2003.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Conventional diuretic agents are very effective agents in relieving volume overload and congestive symptoms in chronic heart failure (CHF). However, they are associated with activation of the renin-angiotensin system (RAS) and the sympathetic nervous system and a reduction in glomerular filtration rate, all of which have been associated with adverse outcomes in CHF. Therefore, there is an increasing interest in drugs that target the natriuretic system without neurohormonal activation and deterioration of renal function. In this review, we will discuss the underlying rationale and evidence behind currently pursued strategies that target the natriuretic system. This includes the administration of natriuretic peptides (NPs) and strategies that potentiate the NP system, such as neutral endopeptidase inhibition. We will also highlight some potentially important interactions of these strategies with drugs that target the RAS.
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Affiliation(s)
- Kok H Chee
- Department of Medicine, University of Malaya, Kuala Lumpur, Malaysia
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Brancaccio G, Michielon G, Di Donato RM, Costa D, Falzea F, Miraldi F. Atrial natriuretic factor in normothermic and hypothermic cardiopulmonary bypass. Perfusion 2016; 19:157-62. [PMID: 15298423 DOI: 10.1191/0267659104pf732oa] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Background: To evaluate the plasmatic changes of atrial natriuretic factor (ANF) during and after cardiopulmonary bypass (CPB) in normothermia and hypothermia. Methods: Twenty-three patients (n=23) undergoing coronary artery bypass graft surgery were randomly assigned to two groups. In Group I (n=11), the patients underwent operation in normothermia; in Group II (n=12), the operation was performed in hypothermia (268C). Results: Plasma ANF levels were determined after induction of anaesthesia, at the end of CPB and one hour postoperatively. There were no demographic differences between the two groups, diuresis (p=0.90) and natriuresis (p=0.95). Plasma levels of ANF were significantly elevated during and after CPB in both groups (p <0.01). The groups differed significantly for plasma levels of ANF during CPB and postoperatively ( p<0.05), but did not differ prebypass (p=0.08). There was no correlation in either group between ANF release and central venous pressure, natriuresis and diuresis. There was only a borderline relationship between ANF concentration and diuresis after CPB in Group I. Conclusion: CPB triggers the production and release of ANF. The present study demonstrates a significantly enhanced ANF release during hypothermia and reperfusion after ischaemia. Thus, these data suggest the protective role of ANF on the hypoxic myocardium, and they confirm that ANF does not play a role in diuresis and natriuresis during and after hypothermic CPB.
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Affiliation(s)
- Gianluca Brancaccio
- Department of Pediatric Cardiac Surgery, Bambino Gesù Hospital, Rome, Italy.
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McDowell G, Nicholls DP. The Therapeutic Potential of Candoxatril, a Neutral Endopeptidase Inhibitor, in Humans. ACTA ACUST UNITED AC 2006. [DOI: 10.1111/j.1527-3466.2000.tb00051.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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McDowell G, Nicholls DP. The endopeptidase inhibitor, candoxatril, and its therapeutic potential in the treatment of chronic cardiac failure in man. Expert Opin Investig Drugs 2005; 8:79-84. [PMID: 15992061 DOI: 10.1517/13543784.8.1.79] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Candoxatril (UK-79300) is the orally-active prodrug of candoxatrilat (UK-73967), the active enantiomer of (+/-)candoxatrilat (UK-69578), a potent neutral endopeptidase (NEP) inhibitor. This article describes the rationale behind the use of such a drug in the treatment of chronic heart failure in man. It further describes the pharmacokinetics and pharmacodynamics of candoxatril in normal healthy individuals and in patients with chronic cardiac failure. In addition, we describe the initial results comparing candoxatril with furosemide and captopril in human heart failure.
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Affiliation(s)
- G McDowell
- Department of Medicine, Royal Victoria Hospital, Grosvenor Road, Belfast, BT12 6BA
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Calderone A. The therapeutic effect of natriuretic peptides in heart failure; differential regulation of endothelial and inducible nitric oxide synthases. Heart Fail Rev 2003; 8:55-70. [PMID: 12652160 DOI: 10.1023/a:1022147005110] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The abnormal regulation of nitric oxide synthase activity represents an underlying feature of heart failure. Increased peripheral vascular resistance, and decreased renal function may be in part related to impaired endothelium-dependent nitric oxide (NO) synthesis. Paradoxically, the chronic production of NO by inducible nitric oxide synthase (iNOS) in heart failure exerts deleterious effects on ventricular contractility, and circulatory function. Consequently, pharmacologically improving endothelium-dependent NO synthesis and the concomitant inhibition of iNOS activity would be therapeutically advantageous. Interestingly, natriuretic peptides have been shown to differentially regulate endothelial NOS (eNOS) and iNOS activity. Moreover, in both patients and animal models of heart failure, pharmacologically increasing plasma natriuretic peptide levels ameliorated vascular tone, renal function, and ventricular contractility. Based on these observations, the following review will explore whether the therapeutic benefit of the natriuretic peptide system in heart failure may occur in part via the amelioration of endothelium-dependent NO synthesis, and the concomitant inhibition of cytokine-mediated iNOS expression.
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Affiliation(s)
- Angelino Calderone
- Centre de Recherche de l'Institut de Cardiologie de Montréal, et Département de Physiologie, Université de Montréal, Montréal, Québec, Canada.
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Uderman H, Vesterqvist O, Manning J, Ferreira I, Delaney C, Liao WC. Omapatrilat: neurohormonal and pharmacodynamic profile when administered with furosemide. J Clin Pharmacol 2001; 41:1291-300. [PMID: 11762556 DOI: 10.1177/00912700122012878] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Pharmacodynamic effects of combination therapy with omapatrilat and furosemide were evaluated. Two groups of 13 healthy subjects each received furosemide 20 mg dailyfor 15 days coadministered with either placebo on days 6 to 15 or omapatrilat 10 mg on days 6 to 10 and 25 mg on days 11 to 15. In the omapatrilat group, urinary excretion of atrial natriuretic peptide increased, and greater blood pressure reductions were seen compared with placebo. Concomitant omapatrilat treatment did not affect the acute diuresis, natriuresis, and kaliuresis observed with chronic administration of furosemide. Neither effective renal plasma flow nor glomerularfiltration rate changed in either treatment group. No clinically significant safety issues were observed. Daily coadministration of omapatrilat 10 or 25 mg with furosemide 20 mg does not affect the pharmacodynamics offurosemide at steady state.
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Affiliation(s)
- H Uderman
- Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey, USA
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Nawarskas J, Rajan V, Frishman WH. Vasopeptidase inhibitors, neutral endopeptidase inhibitors, and dual inhibitors of angiotensin-converting enzyme and neutral endopeptidase. HEART DISEASE (HAGERSTOWN, MD.) 2001; 3:378-85. [PMID: 11975822 DOI: 10.1097/00132580-200111000-00006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Vasopeptidase inhibitors represent a new class of cardiovascular drugs. They function as a combined angiotensin-converting enzyme (ACE) inhibitor and neutral endopeptidase (NEP) inhibitor, the latter of which potentiates the actions of atrial natriuretic peptide (ANP) by minimizing its degradation in the circulation. The consequence of such dual inhibition is a synergistic reduction of vasoconstriction and enhancement of vasodilation, thereby serving to more effectively reduce blood pressure. Furthermore, inhibition of the renin-angiotensin-aldosterone system (RAAS) prevents physiologic compensatory responses in vivo seen with NEP inhibition alone. Vasopeptidase inhibitors have also shown to potentiate bradykinin and adrenomedullin, which additionally contribute to cardiovascular regulation. The most extensively researched and promising agents within the class of VP inhibitors is omapatrilat, a mercaptoacyl derivative of a bicyclic thiazepinone dipeptide. It is a single molecule with equal potency and affinity for ACE and NEP inhibition. Although ACE inhibition tends to more selectively benefit high-renin models of hypertension, vasopeptidase inhibition has been shown to be equally efficacious in low-, normal-, and high-renin models. Contrary to NEP inhibition alone, omapatrilat has also demonstrated the ability to significantly reduce blood pressure in spontaneously hypertensive rats, the equivalent of essential hypertension in humans. Studies also suggest that omapatrilat has cardioprotective properties, especially in the setting of congestive heart failure. More specifically, animal models have demonstrated omapatrilat to be more effective than ACE inhibition alone in remodeling the heart and improving its contractile function. Human studies have documented the efficacy of omapatrilat in the treatment of both hypertension and, to a lesser extent, heart failure. Safety concerns (specifically angioedema) are currently being addressed before the widespread utilization of this promising new agent.
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Affiliation(s)
- J Nawarskas
- Department of Pharmacy, University of New Mexico, Albuquerque, NM, USA
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Blais C, Lapointe N, Rouleau JL, Clément R, Gervais N, Geadah D, Adam A. Effects of the vasopeptidase inhibitor omapatrilat on cardiac endogenous kinins in rats with acute myocardial infarction. Peptides 2001; 22:953-62. [PMID: 11390026 DOI: 10.1016/s0196-9781(01)00401-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The purposes of this study were to evaluate and to compare the effects of simultaneous angiotensin-converting enzyme (ACE) and neutral endopeptidase 24.11 (NEP) inhibition by the vasopeptidase inhibitor omapatrilat (1 mg. kg(-1). day(-1)) with those of the selective ACE inhibitor enalapril (1 mg. kg(-1). day(-1)) on survival, cardiac hemodynamics, and bradykinin (BK) and des-Arg(9)-BK levels in cardiac tissues 24 h after myocardial infarction (MI) in rats. The effect of the co-administration of both B(1) and B(2) kinin receptor antagonists (2.5 mg. kg(-1). day(-1) each) with metallopeptidase inhibitors was also evaluated. The pharmacological treatments were infused subcutaneously using micro-osmotic pumps for 5 days starting 4 days before the ligation of the left coronary artery. Immunoreactive kinins were quantified by highly sensitive and specific competitive enzyme immunoassays. The post-MI mortality of untreated rats with a large MI was high; 74% of rats dying prior to the hemodynamic study. Mortality in the other MI groups was not significantly different from that of the untreated MI rats. Cardiac BK levels were not significantly different in the MI vehicle-treated group compared with the sham-operated rats. Both omapatrilat and enalapril treatments of MI rats significantly increased cardiac BK concentrations compared with the sham-operated group (P < 0.05). However, cardiac BK levels were significantly increased only in the MI omapatrilat-treated rats compared with the MI vehicle-treated group (P < 0.01). Cardiac des-Arg(9)-BK concentrations were not significantly modified by MI, and MI with omapatrilat or enalapril treatment compared with the sham-operated group. The co-administration of both kinin receptor antagonists with MI omapatrilat- and enalapril-treated rats had no significant effect on cardiac BK and des-Arg(9)-BK levels. Thus, the significant increase of cardiac BK concentrations by omapatrilat could be related to a biochemical or a cardiac hemodynamic parameter on early (24 h) post-MI state.
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Affiliation(s)
- C Blais
- Faculté de Pharmacie, Université de Montréal, H3C 3J7, Montréal, (Québec), Canada
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Olivier NB, Kutas SM, Beals S, Hanson B, Windram S. Short-term effects of ecadotril in dogs with induced congestive heart failure. Am J Vet Res 2000; 61:333-8. [PMID: 10714529 DOI: 10.2460/ajvr.2000.61.333] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate short-term hemodynamic effects of ecadotril in a model of congestive heart failure in dogs. ANIMALS 6 conscious adult male dogs. PROCEDURES Instruments were placed in dogs to measure left ventricular, aortic, and atrial blood pressures. Heart failure was induced by repeated coronary embolization with latex microspheres. Four times, and in random order, dogs were given vehicle or active drug (3, 10, or 30 mg/kg of body weight) orally. Hemodynamic variables, urine flow, and urinary electrolyte excretion were measured before and 30, 90, and 150 minutes, and 10 and 21 hours after drug administration. RESULTS Changes in urine flow, heart rate, mean arterial pressure, or peak positive and negative rate of change in ventricular pressure were not apparent. Urinary sodium excretion significantly increased in response to the low and high doses of ecadotril but not in response to the 10 mg/kg dose. Left ventricular end diastolic pressure (LVEDP) consistently decreased in dose- and time-dependent manner. Maximal group-averaged reductions in LVEDP were 5.2, 8.1, and 10 mm Hg for the low, middle, and high doses, respectively. The magnitude of the decrease in LVEDP was not related to cumulative change in urine flow. CONCLUSIONS AND CLINICAL RELEVANCE Orally administered ecadotril reduced left ventricular filling pressures in these dogs by a mechanism that does not require a substantial diuretic effect. Ecadotril may be effective for alleviating clinical signs in dogs with left-sided heart failure and may be particularly beneficial for use in dogs that are refractory to traditional diuretic therapy.
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Affiliation(s)
- N B Olivier
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing 48824, USA
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Loke KE, Laycock SK, Mital S, Wolin MS, Bernstein R, Oz M, Addonizio L, Kaley G, Hintze TH. Nitric oxide modulates mitochondrial respiration in failing human heart. Circulation 1999; 100:1291-7. [PMID: 10491373 DOI: 10.1161/01.cir.100.12.1291] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background-Our objective for this study was to investigate whether nitric oxide (NO) modulates tissue respiration in the failing human myocardium. Methods and Results-Left ventricular free wall and right ventricular tissue samples were taken from 14 failing explanted human hearts at the time of transplantation. Tissue oxygen consumption was measured with a Clark-type oxygen electrode in an airtight stirred bath containing Krebs solution buffered with HEPES at 37 degrees C (pH 7.4). Rate of decrease in oxygen concentration was expressed as a percentage of the baseline, and results of the highest dose are indicated. Bradykinin (10(-4) mol/L, -21+/-5%), amlodipine (10(-5) mol/L, -14+/-5%), the ACE inhibitor ramiprilat (10(-4) mol/L, -21+/-2%), and the neutral endopeptidase inhibitor thiorphan (10(-4) mol/L, -16+/-5%) all caused concentration-dependent decreases in tissue oxygen consumption. Responses to bradykinin (-2+/-6%), amlodipine (-2+/-4%), ramiprilat (-5+/-6%), and thiorphan (-4+/-7%) were significantly attenuated after NO synthase blockade with N-nitro-L-arginine methyl ester (10(-4) mol/L; all P<0.05). NO-releasing compounds S-nitroso-N-acetyl-penicillamine (10(-4) mol/L, -34+/-5%) and nitroglycerin (10(-4) mol/L, -21+/-5%), also decreased tissue oxygen consumption in a concentration-dependent manner. However, the reduction in tissue oxygen consumption in response to S-nitroso-N-acetyl-penicillamine (-35+/-7%) or nitroglycerin (-16+/-5%) was not significantly affected by N-nitro-L-arginine methyl ester. Conclusions-These results indicate that the modulation of oxygen consumption by both endogenous and exogenous NO is preserved in the failing human myocardium and that the inhibition of kinin degradation plays an important role in the regulation of mitochondrial respiration.
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Affiliation(s)
- K E Loke
- Department of Physiology, New York Medical College, Valhalla, NY, USA
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