Cardiovascular effects of natriuretic peptides and their interrelation with endothelin-1

The natriuretic peptides are a group of structurally related but genetically distinct peptides. Four types of natriuretic peptides have been found thus far: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), C-type natriuretic peptide (CNP) and Dendroaspis natriuretic peptide (DNP). ANP and BNP are secreted mainly from the heart and function as hormones with vasodilatory and natriuretic effects. CNP originates mainly from endothelial cells with a paracrine effect to induce vasodilation. Other effects of natriuretic peptides including negative inotropy, antimitogenic and anticoagulation have been described. Three types of natriuretic peptide receptors mediate their functions, and among them two are cGMP-coupled. Clearance of natriuretic peptides is via its clearance receptor through the action of neutral endopeptidases. Natriuretic peptides interact with other vasoactive peptides including endothelin. The putative role of natriuretic peptides in the pathophysiology of various cardiovascular diseases including congestive heart failure, hypertension, ischemic heart disease, and cardiomyopathy are discussed. Natriuretic peptide plasma levels are used for the diagnosis and therapeutic follow-up of congestive heart failure patients. Increasing the levels of natriuretic peptides by natriuretic peptide mimetics and neutral endopeptidase inhibitors may provide a new therapeutic strategy for the treatment of cardiovascular diseases such as congestive heart failure and hypertension.     

Functional compartmentation of the endocrine action of cardiac natriuretic peptides

The endocrine function of the heart is to secrete Atrial and Brain natriuretic -peptides (ANP and BNP). These peptides are biologically active via particulate guanylate cyclases which generate cyclic GMP, the second intracellular messenger. A polysaccharide antagonist, HS-142-1 has been recently described by a Japanese Group. Cyclic GMP is partly secreted from the target cells into the extra cellular medium in which its accumulation is proportional to the concentration of the natriuretic peptide. Neutral Endopeptidase (NEP) is a zinc ectoenzyme involved in the catabolism of natriuretic peptides. NEP is absent in plasma but present on the surface of endothelial and smooth muscle cells. NEP is mainly expressed at the apical pole of the epithelial cells of the proximal tubule in the nephron. Chronic increase in volume and pressure within the cardiac cavities is associated with the oversecretion of natriuretic peptides. This chronic phenomenon involves the recruitment of all the cardiac myocytes to express natriuretic peptide genes. The clinical application of this hyperplasic phenomenon is congestive heart failure, in which the plasma levels of natriuretic peptides correlate with the level of the -hemodynamic stress. Therefore the plasma levels of natriuretic peptides are good pronostic markers in both experimental and human heart failure. The degree of congestive heart failure as well as the plasma levels of ANP and BNP are also -correlated with the plasma and urinary levels of cyclic GMP. The plasma level of -cyclic GMP is correlated with the endothelial concentration of cyclic GMP but not with the cyclic GMP concentration in smooth muscle cells. From these experimental data, we can conclude that plasma cyclic GMP originates from endothelial cells and is related to particulate guanylate cyclase activity. In contrast natriuretic peptides do not modulate vascular wall cyclic GMP content. The natriuretic action of ANP is probably due to the interaction of the filtered peptide with the particulate guanylate cyclase at the apical pole of the epithelial cells. The apparition of peptiduria associated with natriuresis during NEP inhibition provides evidence of the action of the peptide in the urinary compartment. It is also by a urinary pathway via the macula densa that ANP, and its potentiation by NEP inhibition, decreases renin secretion. The fact that plasma levels of ANP and plasma and urine levels of cyclic GMP correlate with the degree of salt retention in congestive heart failure, provides evidence for chronic desensitization of the system. An up-regulation of Na(+), K(+), 2Cl(-) expression associated with experimental congestive heart failure has recently been shown. Similarly, a modulation of the different sodium transporter systems along the nephron could be one of the counter-regulations leading to desensitization to natriuretic peptides. In conclusion, natriuretic peptides are true endocrine peptides, secreted by the heart, transported in the plasma, filtered by the glomeruli and active at the nephron level. The molecular effector of ANP and cyclic GMP in the epithelial cells is probably the G-kinase II, isoform phosphorylating the cystic fibrosis transmembrane conductance regulator (CFTR). The exact mechanism of desensitization remains to be elucidated.     

Natriuretic peptides in the pathophysiology of congestive heart failure

A hallmark of congestive heart failure (CHF) is the activation of the cardiac endocrine system, in particular atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). The natriuretic peptides are a group of structurally similar but genetically distinct peptides that have diverse actions in cardiovascular, renal, and endocrine homeostasis. ANP and BNP are of myocardial cell origin and C-type natriuretic peptide (CNP) is of endothelial origin. ANP and BNP bind to the natriuretic peptide-A receptor (NPR-A), which, via 3',5'-cyclic guanosine monophosphate (cGMP), mediates natriuresis, vasodilatation, renin inhibition, antimitogenesis, and lusitropic properties. CNP lacks natriuretic actions but possesses vasodilating and growth inhibiting actions via the guanylyl cyclase-linked natriuretic peptide-B receptor. All three peptides are cleared by the natriuretic peptide-C receptor and degraded by the ectoenzyme neutral endopeptidase 24.11, both of which are widely expressed in kidney, lung, and vascular wall. Recently, a fourth member of the natriuretic peptide, Dendroaspis natriuretic peptide (DNP) has been reported to be present in human plasma and atrial myocardium and is elevated in plasma of human CHF.     

Role of nisoldipine on blood pressure, cardiac hypertrophy, and atrial natriuretic peptides in spontaneously hypertensive rats

The effect of long-term treatment with the calcium antagonist nisoldipine on development of hypertension, cardiac hypertrophy, and plasma levels of atrial natriuretic peptides (ANP) was determined in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) of the same age. Measurement of immunoreactive ANP in plasma provided a sensitive marker for the severity of hypertension and the associated cardiac overload. Long-term treatment with nisoldipine prevented the development of hypertension, the associated heart failure, and the increase of plasma levels of ANP in SHR but had no effect on systolic blood pressure, heart weight, and plasma levels of ANP in WKY. In addition, nisoldipine had a therapeutic effect in old SHR with manifest cardiac failure in end-stage hypertension, as evidenced not only by the reduction of blood pressure but also by the reduction of cardiac hypertrophy, of elevated immunoreactive ANP in plasma, and of increased plasma renin activity.     

Pathophysiologic and prognostic considerations in circulatory insufficiency in congestive heart failure: receptor function

We measured plasma concentrations of norepinephrine, cyclic AMP, cyclic GMP, atrial natriuretic peptides (ANP) and beta-adrenoceptor density (Bmax) and affinity (Kd) of lymphocytes in patients with congestive heart failure and correlated these parameters with symptoms and hemodynamic indices. Plasma concentration of norepinephrine, cyclic AMP, cyclic GMP and ANP significantly increased in patients with congestive heart failure. Plasma concentrations of norepinephrine were related to the severity of the heart failure, plasma cyclic AMP concentrations, and pulmonary artery pressures. Cyclic AMP concentrations fell rapidly after treatment of acute left ventricular failure. Peripheral blood lymphocytes were stimulated by isoproterenol, and cyclic AMP level in lymphocytes was assayed. In normal subjects the generation of cyclic AMP after stimulation decreased with age. The response of lymphocytes in patients of NYHA classes III and IV was significantly lower than in the normal age-matched controls. A significant correlation between plasma norepinephrine concentration and increase of lymphocyte cyclic AMP was demonstrated. From these results it was suggested that beta-adrenergic receptors in congestive heart failure were desensitized. Beta receptor numbers of lymphocytes significantly decreased in NYHA class III and IV, but did not decrease in class I and II. There was no significant difference in Kd associated with congestive heart failure. Plasma concentrations of cyclic GMP also depended on the severity of heart failure and the pulmonary artery pressure, and decreased sharply with treatment, although remaining at a high value. A significant correlation between the cyclic GMP and ANP concentration was found in patients with congestive heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regulation of receptors for atrial natriuretic peptide in the rat and human

Summary Atrial natriuretic factor or peptide (ANP) is a peptide recently isolated from mammalian atria with potent natriuretic, vasorelaxant, and aldosterone-inhibitory properties. ANP may glay an important role in the regulation of blood pressure and body salt and fluid balance. The presence of binding sites for ANP in the vasculature and adrenal glomerulosa of rats and in platelets in humans has been demonstrated. These sites are involved in the mediation of the vasorelaxant effect of ANP and its inhibitory action on aldosterone seeretion. The role of binding sites on platelets is unknown, but the availability of platelets makes them a useful model for investigating the regulation of receptors for atrial natriuretic factor in humans. The effect of sodium depletion and loading and mineralocorticoids on the density of rat vascular and adrenal sites for ANP was examined, as well as changes that occur after development of renovascular and DOCA-salt hypertension in rats. Sodium loading in the presence of reduced renal mass (unilateral nephrectomy) or mineralocorticoid administration produced renin suppression and resulted in down-regulation of vascular ANP receptors. In one-kidney, one-clip Goldblatt hypertensive rats and in DOCA-salt hypertensive rats, two models of volume-expanded, non-renin-dependent experimental hypertension, the density of ANP binding sites in the mesenteric arterioles was significantly decreased. The sensitivity to ANP of precontracted aorta from renovascular and mineralocortieoid hypertensive rats was significantly reduced. No consistent changes occured in the density of ANP binding sites in the adrenal glomerulosa. Thus, in normotensive or hypertensive animals with volume expansion, a condition which produces increases in circulating ANP, ANP receptors in blood vessels were down-regulated. In cultured rat vascular smooth muscle cells, exposure to 10 nM ANP for 24 hours resulted in down-regulation of ANP binding sites. In humans, binding sites for ANP in platelets had the same molecular requirements as vascular ANP sites in the rat. Sodium loading of normal human volunteers resulted in increased concentration of ANP in plasma and decreased density of ANP binding sites in platelets. In patients with severe congestive heart failure, and elevated concentration of ANP in plasma, the density of ANP sites on platelets was significantly decreased. ANP binding sites in human platelets are regulated similarly to ANP vascular receptors in the rat and may therefore serve as a model for the study of vascular ANP receptors in humans. Increased plasma ANP down-regulates ANP receptors in the rat and human beings. Decreased vascular relaxation secondary to reduced responsiveness to ANP due to down-regulated ANP receptors may play a role in elevation of blood pressure in some models of experimental hypertension. Decreased density of ANP receptors may contribute to the sodium retention of severe congestive heart failure in humans.     

Atrial peptides, ANP(1-98) and ANP(99-126) in health and disease in an elderly population

Circulating immunoreactive atrial natriuretic peptide, Ir ANP(99-126)and the N-terminal fragment of the prohormone, Ir ANP(1–98)were measured in two population samples from the general populationof Gothenburg, Sweden. A group of 85-year olds (974 subjects)and a group of 40-year olds (191 subjects) were investigatedin respect of cardiovascular, renal and metabolic disease. Ir ANP(99-126) and Ir ANP(1-98) were significantly higher inthe 85-year olds compared to tile 40-year olds, and were significantlyincreased in subjects with congestive heart failure, ischaemicheart disease, atrial fibrillation and renal dysfunction butnot in subjects with hypertension. Eighty-five-year-old subjectswho were on treatment with digitalis, ß-adrenergic-blockers,nitrates and diuretics had significantly increased Ir ANP(99-126)and Ir ANP(1-98). In multivariate analysis Ir ANP(99-126) concentrationswere predictive for congestive heart failure, ischaemic heartdisease, atrial fibrillation and treatment with ß-blockersand anti-depressant drugs. Ir ANP(1–98) was predictivefor congestive heart failure, ischaemic heart disease, atrialfibrillation, diabetes mellitus, renal failure and drug treatmentwith ß-blockers and neuroleptics. We conclude that measurements of circulating concentrationsof Ir ANP(99-126) and/or Ir ANP(1-98) may add valuable informationin the diagnosis of congestive heart failure and ischaemic heartdisease in an elderly population. It remains to be determinedwhether routine measurements of circulating Ir ANP(99–126)and Ir ANP(1–98) may be of value in predicting currentcardiovascular disease for the individual patient.     

Atrial natriuretic peptide in congestive heart failure in the dog: plasma levels, cyclic guanosine monophosphate, ultrastructure of atrial myoendocrine cells, and hemodynamic, hormonal, and renal effects

In an animal preparation of congestive heart failure in the dog, during the development of cardiac failure due to rapid right ventricular pacing we observed significant decreases in cardiac output and arterial pressure and increases in pulmonary arterial and right atrial pressure. We also observed a related increase in right atrial pressure and increases in plasma levels of atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (c-GMP). Ultrastructure changes in the atrial myoendocrine cells indicated extreme stimulation of the secretory apparatus of ANP. The response of hemodynamic, renal, and hormonal variables was investigated after incremental infusions (0.01, 0.03, 0.1, 0.3, and 0.06 microgram/kg/min) of exogenous ANP. In healthy animals ANP significantly decreased mean arterial pressure, cardiac output, stroke volume, and right atrial pressure without changing heart rate or peripheral vascular resistance. As expected, we found a striking increase in urine flow and urinary excretion of sodium, chloride, magnesium and calcium and a smaller increase in potassium excretion. ANP suppressed renin secretion, and increased renal plasma flow, glomerular filtration rate, and filtration fraction. In dogs with heart failure ANP caused a small reduction in mean arterial pressure. No effect was seen on other hemodynamic variables or plasma renin concentration. The excretory effects on the kidneys were completely absent, and smaller increases in glomerular filtration rate and filtration fraction were observed. We found no difference between healthy dogs and animals with heart failure with respect to the secretion of c-GMP during ANP infusions in relation to the plasma levels of ANP. This suggests an intracellular defect that prevents the mediation of the hormonal signal into biological action in the presence of heart failure.     

Historical perspectives on the renin-angiotensin-aldosterone system and angiotensin blockade

Advances leading to recognition of the relation of the renin-angiotensin system to aldosterone include: (1) development of analytic techniques for measuring aldosterone, (2) discovery of an aldosterone-stimulating factor in circulating plasma, (3) the finding that a potent aldosterone-stimulating factor is secreted by the kidney, (4) evidence that synthetic angiotensin II increases aldosterone secretion, (5) fractionation of crude kidney extracts and the finding that aldosterone-stimulating factor is renin, (6) the observation that high plasma renin activity occurs in secondary aldosteronism, and (7) recognition that the renin-angiotensin-aldosterone system occurs in congestive heart failure and in renovascular and malignant hypertension. The early use of blocking agents for the renin-angiotensin system is described along with the landmarks of progress. These include the observations that: (1) arterial pressure decreases in experimental renovascular hypertension in response to angiotensin blockade, (2) angiotensin provides important support for arterial pressure in low cardiac output states including congestive heart failure, (3) the kidney participates in this important compensatory mechanism, and (4) cellular receptors for angiotensin are present in the two inner zones of the adrenal cortex.     

大鼠充血性心力衰竭时内皮素改变及心钠素的影响

本文应用放射免疫方法,研究实验性充血性心衰大鼠的血浆及肾组织内皮素浓度的改变,及静脉给予心钠素后的影响.结果显示,心衰大鼠的血浆内皮素浓度(93.9±25.4ng/L)及肾组织内皮素浓度(51.2±12.8ng/G)均明显升高(P<0.05,P<0.01).同时心钠素的血浆浓度(252.9±58.7ng/L)也明显升高(P<0.05).静脉给予心钠素(30μg)后,心衰大鼠血浆内皮素浓度(245.0±41.3ng/L)显著升高(P<0.001),但与对照组比差别无显著性.给心钠素后肾组织内皮素浓度(37.8±8.5ng/G)显著降低(P<0.01),但仍高于对照组(P<0.01).表明心衰时内皮素的合成释放明显增强,肾组织内皮素合成增强更为显著.心钠素刺激内皮素的合成、释放.肾组织内皮素浓度升高可能是心衰时拮抗心钠素利钠、利尿效应的重要机制之一.提示阻断、抑制内皮素的作用,可能改善心衰预后.     

One year temporal pattern of neurohumoral factors and natriuretic peptides compared with clinical variables in patients with dilated cardiomyopathy

BACKGROUND: Elevated levels of neuroendocrine peptides and hormones are some of the compensatory mechanisms activated in patients with congestive heart failure. The aim of this study was to describe their time related variability in clinically stable patients and to compare hormones and peptides levels to clinical variables. METHODS: Nineteen patients with history of congestive heart failure due to dilated cardiomyopathy and in sinus rhythm were recruited. At baseline, after 3 months, and at 1 year they underwent 6-min walk test, Minnesota Living with Heart Failure Questionnaire, and blood measurements of ANP, BNP, plasma renin activity, aldosterone, norepinephrine and epinephrine. RESULTS: After 1 year, 17 patients remained clinically stable, and did not change their therapy and functional class. Also echocardiographic data and neurohormonal parameters did not change significantly except for epinephrine that decreased significantly after 3 months and returned to a value similar to the basal one at 1 year. Two outliner values were observed for norepinephrine belonging to the only 2 patients that spontaneously withdrew the ace-inhibitor therapy during the follow-up. CONCLUSIONS: This study indicates that plasma concentration of neurohormones and peptides were fairly stable over 1 year interval in stable patients with mild-moderate heart failure due to dilated cardiomyopathy and that norepinephrine could be considered as the most sensible parameters to monitor therapy compliance.     

Cytokines and remodeling of the heart in patients with congestive heart failure

Proinflammatory cytokines are capable of modulating cardiovascular function by a various mechanisms. The aim of the study was to evaluate the influence of the selected cytokines: tumor necrosis factor alpha (TNF-alpha), interleukin 1 (IL-1), interleukin 2 (IL-2), interleukin 6 (L-6), endothelin 1 (ET-1) on the remodeling of the heart in patients with congestive heart failure (1-year follow-up). The study was made in 45 patients with congestive heart failure treated in the Department of Cardiology. Of these, 31 were men aged from 44 to 77 and 14 were women aged from 48 to 79. Ischaemic heart disease was diagnosed in 22 patients and ischaemic heart disease and hypertension in 10 patients, dilated cardiomyopathy was diagnosed in 6 patients and postinflammatory cardiomyopathy in 7 patients. Blood samples for determination of TNF-alpha, IL-1, IL-2, IL-6, ET-1, aldosterone, catecholamines, brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) levels were obtained prior to the treatment and in 3 and 6 and 12 month follow-up. At the same time were estimated: NYHA functional class, structure, systolic and diastolic left ventricle function of the heart using echocardiography and 24-hour ECG Holter monitoring (HR, supraventricular and ventricular arrhythmias). TNF-alpha, IL-1, IL-2, IL-6, ET-1, aldosterone, catecholamines, BNP and ANP plasma levels were determined with radioimmunological assay. In patients with progression of congestive heart failure (worsening of NYHA class and ejection fraction of left ventricle) the plasma concentrations of TNF-alpha and ET-1 significantly increased in following observations. In this group patients we determined a correlation between ejection fraction of the left ventricle and serum concentration of TNF-alpha and ET-1. In patients with improving of NYHA functional class and ejection fraction of left ventricle the plasma concentrations of cytokines were not altering. In all patients the plasma concentration of TNF-alpha correlated with ANP and BNP concentrations.     

Role of urotensin II in atherosclerotic cardiovascular diseases

Urotensin II (U-II) is a powerful vasoconstrictor peptide with a potency greater than that of endothelin 1. Its plasma level correlates positively with body weight and is raised in diabetes, renal failure, hypertension, and other cardiovascular diseases, including congestive heart failure and carotid atherosclerosis. Experimental and clinical studies have revealed increased expression of U-II and U-II receptor (UT) in animals with experimentally induced myocardial infarction, heart failure, and in patients with hypertension, atherosclerosis, and diabetes, suggesting a potential role for U-II in coronary artery disease. Peptide and nonpeptide UT ligands have been shown to be effective in antagonizing the effects of U-II in the cardiovascular system. This article aims to review recent advances in physiology and pathophysiology of U-II with particular reference to its role in atherosclerotic cardiovascular diseases.     

The potential of brain natriuretic peptide as a biomarker for New York Heart Association class during the outpatient treatment of heart failure

BACKGROUND: Plasma C-terminal atrial natriuretic peptide (C-ANP), N-terminal ANP (N-ANP), and brain natriuretic peptide (BNP) have diagnostic utility in detecting left ventricular dysfunction. Their relative value in monitoring symptom status during the chronic treatment of congestive heart failure (CHF) remains undefined. METHODS AND RESULTS: Ninety-eight subjects with CHF were evaluated. Baseline natriuretic peptides were measured by radioimmunoassay, left ventricular ejection fraction (LVEF) was estimated with echocardiography, and New York Heart Association (NYHA) class was determined independently by attending heart failure specialists. Forty-one subjects were restudied during a 6- to 12-month follow-up period after optimizing therapy. At baseline, all natriuretic peptides and LVEF correlated positively with NYHA class (P <.005). Plasma BNP, however, correlated best with NYHA class. At follow-up, only changes of BNP correlated to changes of NYHA class (P =.04). BNP decreased (-45% +/- 12%, N = 14, P =.002) in subjects whose NYHA class improved whereas BNP remained unchanged (-1% +/- 10%, N = 25, P =.95) in those whose NYHA class was stable. CONCLUSIONS: This investigation demonstrates the superiority of plasma BNP as compared to ANP and LVEF in objectively assessing NYHA class during the chronic treatment of CHF. Given that clinical assessment of CHF is subjective, plasma BNP is a useful objective biomarker in monitoring human CHF in the outpatient setting.     

Marked Elevation of Brain Natriuretic Peptide Levels in Pericardial Fluid Is Closely Associated With Left Ventricular Dysfunction

Objectives. The purpose of this study was to investigate whether atrial and brain natriuretic peptides (ANP and BNP, respectively) represent autocrine/paracrine factors and are accumulated in pericardial fluid.Background. ANP and BNP, systemic hormones produced by the heart, have elevated circulating levels in patients with heart failure. Recent evidence suggests that the heart itself is one of the target organs for these peptides.Methods. With an immunoreactive radiometric assay, we measured the concentrations of these peptides in plasma and pericardial fluid simultaneously in 28 patients during coronary artery bypass graft surgery.Results. The pericardial levels of BNP were markedly elevated in patients with impaired left ventricular function. We investigated the correlation of ANP and BNP levels in plasma or pericardial fluid with left ventricular hemodynamic variables. None of the hemodynamic variables correlated with ANP levels in plasma or pericardial fluid. Both plasma and pericardial fluid levels of BNP were significantly related to left ventricular end-diastolic and systolic volume indexes (LVEDVI and LVESVI, respectively). In addition, BNP pericardial fluid levels had closer relations with LVEDVI (r = 0.679, p < 0.0001) and LVESVI (r = 0.686, p < 0.0001) than did BNP plasma levels (LVEDVI: r = 0.567, p = 0.0017; LVESVI: r = 0.607, p = 0.0010). BNP levels in pericardial fluid but not in plasma correlated with left ventricular end-diastolic pressure (r = 0.495, p = 0.0074).Conclusions. BNP levels in pericardial fluid served as more sensitive and accurate indicators of left ventricular dysfunction than did BNP levels in plasma. Thus, BNP may be secreted from the heart into the pericardial space in response to left ventricular dysfunction, and it may have a pathophysiologic role in heart failure as an autocrine/paracrine factor.     

Plasma levels of adrenomedullin and atrial and brain natriuretic peptides in the general population: their relations to age and pulse pressure.

Adrenomedullin (AM) and atrial and brain natriuretic peptides (ANP and BNP) exert vasodilator and natriuretic actions and are thought to share roles in counteracting the progression of hypertension or heart failure as circulating or locally-acting hormones. However, little data is available with regard to their roles in subjects who have no apparent cardiovascular diseases. The present study was carried out to identify the factors that affect plasma levels of AM, ANP and BNP in the general population. We measured the plasma levels of AM, ANP and BNP in 184 local residents who had a scheduled regular health checkup, and compared the findings with those for other clinical parameters. Univariate analyses showed that the plasma levels of AM, ANP and BNP were significantly correlated with age. The plasma levels of ANP and BNP were also significantly correlated with systolic blood pressure (SBP) and with pulse pressure (PP), an indicator of the stiffness of the great vessels. Multivariate analyses conducted using a stepwise method revealed that age was a significant, independent variable for the plasma levels of AM, ANP and BNP. In addition, PP was a significant factor for the plasma levels of ANP and BNP, while the plasma AM was significantly associated with body mass index (BMI). Thus, the plasma levels of AM, ANP and BNP all increased in association with aging, and those of ANP and BNP increased in association with PP, suggesting possible relationships between the plasma levels and age-related changes in the cardiovascular system.     

Natriuretic peptide family]

The natriuretic peptide system consists of at least three endogenous ligands: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP), and three receptors, ANP-A receptor (guanylate cyclase A), ANP-B receptor (guanylate cyclase B) and clearance receptor (C receptor). ANP, the prototype of natriuretic peptides, is mainly produced in the atrium and secreted into the circulation as a cardiac hormone. ANP is also produced in the ventricle and in the central nervous system. BNP, first isolated from the porcine brain, has a marked divergence in its molecular size and sequence among species. In humans and rats, the major site of production of BNP is the ventricle of the heart. BNP is also secreted into the circulation as a cardiac hormone. The plasma BNP level in normal subjects is approximately one sixths of the plasma ANP level; however, the plasma BNP level markedly increases in heart failure, renal failure and hypertension and the augmentation of the BNP secretion is much larger than that of the ANP secretion. In addition, clearance of BNP from the circulation is slower than that of ANP. Furthermore, BNP is secreted more urgently than ANP in acute heart failure. CNP distributes mainly in the central nervous system and pituitary gland. No significant amount of CNP is detectable in the heart and plasma. Thus, CNP is a local regulator rather than a cardiac hormone. Three natriuretic receptors have ligand selectivity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Possible vascular role of increased plasma arginine vasopressin in congestive heart failure

BACKGROUND: The present study was undertaken to determine the relation of cardiac dysfunction with hormonal release in patients with congestive heart failure. METHODS: Seventy-two patients with congestive heart failure were examined, who were divided into four subgroups classified by the criteria of the New York Heart Association (NYHA). Also, 10 age-matched subjects were served as a control. Plasma arginine vasopressin (AVP), norepinephrine, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were determined. Cardiac index and pulmonary capillary wedge pressure (PCWP) were measured in 51 of 72 patients. RESULTS: Plasma AVP levels were significantly increased according to the severity of NYHA classes; control: 1.7 +/- 0.2; NYHA I: 4.9 +/- 0.8, NYHA II: 5.5 +/- 0.9, NYHA III: 13.4 +/- 2.6 (p < 0.05), NYHA IV: 26.9 +/- 5.6 pmol/l (p < 0.001). Similar results were obtained with plasma norepinephrine, ANP and BNP. Plasma AVP levels had negative correlation with cardiac index (r = -0.36, p < 0.01), but did not with PCWP and plasma osmolality. Plasma BNP levels positively correlated with PCWP (r = 0.44, p < 0.001), but did not with cardiac index. There was no correlation between plasma AVP and BNP. Intensive therapy profoundly reduced all the hormones according to the improvement of cardiac index in the patients with NYHA class III and IV. The percent decrease in plasma AVP was 60.0%, a value greater than that in plasma BNP. CONCLUSION: The present study indicates that increased AVP may deteriorate cardiac function through V(1a) as well as V(2) action, and that plasma AVP level is also a proper marker for the presence and severity of congestive heart failure.     

Opposite regulation of brain and C-type natriuretic peptides in the streptozotocin-diabetic cardiopathy

C-type natriuretic peptide (CNP), a recent addition to the family of natriuretic peptides including atrial and brain natriuretic peptide (ANP, BNP), is believed to be an endothelium-derived vasodilator and to have an antimitotic effect. ANP and BNP concentrations are increased in conditions such as congestive heart failure, but cardiac CNP concentrations have not been investigated in this connection. Diabetes mellitus also involves myocardial dysfunctions without coronary artery disease or systemic hypertension. We therefore investigated the cardiac expression of CNP mRNA compared with that of BNP mRNA in streptozotocin (STZ)-diabetic rats. STZ- diabetic male Wistar rats (n=6) were studied in comparison with controls (n=6). The animals were characterised by their mean arterial blood pressure and plasma glucose concentrations. After extraction of total cardiac RNA, a specific cDNA probe of BNP was used for northern blot analysis, whereas myocardial CNP expression was analysed by an RNase-protection assay. Twelve weeks after diabetes was induced, the rats were normotensive (96.4+/-2.0 compared with 95.1+/-1.9 mmHg) and hyperglycaemic (615+/-61 compared with 165+/-21 mg/dl; P<0.001). Left ventricular pressure was significantly impaired (76.8+/-6.4 compared with 51.2+/-3.6 mmHg). STZ-diabetic rats had a 3.2-fold increase in cardiac BNP expression compared with controls. In contrast, cardiac CNP mRNA concentrations were decreased 2.6-fold. CNP seems to be downregulated like other peptides with antimitotic and vasodilator activities (nitric oxide, prostacyclin, kinins). This may contribute to cardiac dysfunction in diabetes mellitus and suggests that stimulation of CNP expression could provide cardiac protection in such cases.