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Biomarker discovery efforts in serum and plasma are greatly hindered by the presence of high abundance proteins that prevent the detection and quantification of less abundant, yet biologically significant, proteins. The most common method for addressing this problem is to specifically remove the few abundant proteins through immunoaffinity depletion/subtraction. Herein, we improved upon this method by utilizing multiple depletion columns in series, so as to increase the efficiency of the abundant protein removal and augment the detection/ identification of less abundant plasma proteins. Spectral counting was utilized to make quantitative comparisons between undepleted plasma, plasma depleted with a single depletion column, and plasma depleted using two or three depletion columns in tandem. In the undepleted plasma only 29 lower abundance protein groups were identified with the top-scoring protein from each group having a median spectral count of 3, while in the plasma processed using a single HSA depletion column 61 such protein groups were identified with a median spectral count of 8. In comparison, 76 lesser abundant protein groups were identified with a median spectral count of 11.5 in the two column setup (i.e., HSA followed by MARS Hul4). However, in the ultimate depleted plasma sample, which was created using three depletion columns in tandem, the number of less abundant protein groups identified increase to 81 and the median spectral count for the top-scoring proteins from each group increased to 15 counts per protein. Moreover, exogenous B-type natriuretic peptide-32, which was added to the plasma as a detection benchmark at 12 [micro]g/mL, was only detected in the plasma sample depleted using three depletion columns in tandem. Collectively, these data demonstrate that this method, tandem removal of abundant proteins or TRAP, provides superior removal efficiency compared to traditional applications and improves the depth of proteome coverage in plasma. 10.1021/ac102248d

Alternative RNA splicing may provide unique opportunities to identify drug targets and therapeutics. We identified an alternative spliced transcript for B-type natriuretic peptide (BNP) resulting from intronic retention. This transcript is present in failing human hearts and is reduced following mechanical unloading. The intron-retained transcript would generate a unique 34 amino acid (aa) carboxyl terminus while maintaining the remaining structure of native BNP. We generated antisera to this carboxyl terminus and identified immunoreactivity in failing human heart tissue. The alternatively spliced peptide (ASBNP) was synthesized and unlike BNP, failed to stimulate cGMP in vascular cells or vasorelax pre-constricted arterial rings. This suggests that ASBNP may lack the dose-limiting effects of recombinant BNP. Given structural considerations, a carboxyl-terminal truncated form of ASBNP was generated (ASBNP.1) and was determined to retain the ability of BNP to stimulate cGMP in canine glomerular isolates and cultured human mesangial cells but lacked similar effects in vascular cells. In a canine-pacing model of heart failure, systemic infusion of ASBNP.1 did not alter mean arterial pressure but increased the glomerular filtration rate (GFR), suppressed plasma renin and angiotensin, while inducing natriuresis and diuresis. Consistent with its distinct in vivo effects, the activity of ASBNP.1 may not be explained through binding and activation of NPR-A or NPR-B. Thus, the biodesigner peptide ASBNP.1 enhances GFR associated with heart failure while lacking the vasoactive properties of BNP. These findings demonstrate that peptides with unique properties may be designed based on products of alternatively splicing. vasoactive | myocardial | kidney

32-amino acid B-type natriuretic peptide (BNP 1-32) plays an important role in cardiovascular homeostasis. Recently, it was reported that BNP 1-32 is cleaved by the metalloprotease meprin A to BNP 8-32, the bioactivity of which is undefined. We hypothesized that BNP 8-32 has reduced vasodilating and natriuretic bioactivity compared with BNP 1-32 in vivo. Human BNP 8-32 and BNP 1-32 were compared in a crossover study in eight anesthetized normal canines. After a pre-infusion clearance, BNP 1-32 was infused at 30 ng x [kg.sup.-1] x [min.sup.-1] for 45 min followed by a 60-min washout and a second preinfusion clearance. Then, equimolar BNP 8-32 was infused. In half of the studies, the peptide sequence was reversed. Changes with peptides from the respective preinfusion clearance to infusion clearance were compared with paired tests. Mean arterial pressure was reduced by both BNP 8-32 and BNP 1-32 (-8 [+ or -] 3 vs. -6 [+ or -] 2 mmHg, P = 0.48). Changes in right atrial pressure, pulmonary capillary wedge pressure, heart rate, cardiac output, and glomerular filtration rate were similar. However, urinary sodium excretion increased less with BNP 8-32 than with BNP 1-32 (+171 [+ or -] 24 vs. +433 [+ or -] 43 [micro]Eq/min; P = 0.008), as did urinary potassium excretion, urine flow, and renal blood flow. While BNP 8-32 has similar vasodilating actions as BNP 1-32, its diuretic and natriuretic actions are reduced, suggesting a role for meprin A in the regulation of BNP 1-32 bioactivity in the kidney. Meprin A inhibition may be a potential strategy to increase the bioactivity of endogenous and exogenous BNP 1-32 in cardiovascular diseases. hormone; peptidase; cardiorenal regulation; natriuretic peptides

A study was conducted to examine the mechanism by which a mutation in NPPA could lead to a familial atrial fibrillation. Findings indicated that in families with atrial fibrillation, investigators have identified mutations in ion channels that are predicted to shorten or lengthen the duration of cardiac action potentials.

A study was conducted to evaluate the predictive value of QRS duration in patients who have been hospitalized with heart failure wit reduced left ventricular ejection fraction (LVEF). Results indicate that QRS is an effective indicator of high morbidity and mortality after discharge.

Worsening renal function in the setting of human acute heart failure (AHF) predicts poor outcomes, such as rehospitalization and increased mortality. Understanding potential renoprotective mechanisms is warranted. The guanylate cyclase (GC) enzymes and their second messenger cGMP are the target of two important circulating neurohumoral systems with renoprotective properties. Specifically, natriuretic peptides (NP) released from the heart with AHF target particulate GC in the kidney, while the nitric oxide (NO) system is an activator of renal soluble GC. We hypothesized that both systems are essential to preserve renal excretory and hemodynamic function in AHF but with distinct roles. We investigated these roles in three groups of anesthetized dogs (6 each) with AHF induced by rapid ventricular pacing. After a baseline AHF clearance, each group received intrarenal vehicle (control), [N.sup.G]-monomethyl-L-arginine (L-NMMA), a competitive NO inhibitor (50 [micro]g x [kg.sup.-1] x [min.sup.-1]) or a specific NP receptor antagonist, HS-142-1 (0.5 mg/kg). We observed that intrarenal L-NMMA decreased renal blood flow (RBF) without significant decreases in glomerular filtration rate (GFR), urinary sodium excretion (UNaV), or urinary cGMP. In contrast, HS-142-1 resulted in a decrease in UNaV and cGMP excretion together with a reduction in GFR and an increase in distal fractional tubular sodium reabsorption. We conclude that in AHF, the NP system plays a role in maintaining sodium excretion and GFR, while the function of NO is in the maintenance of RBF. These studies have both physiological and therapeutic implications warranting further research into cardiorenal interactions in this syndrome of AHF.

A study was conducted to evaluate short-term effects of tolvaptan when added to standard therapy in patients hospitalized with heart failure (HF). It was observed that in patients hospitalized with HF, oral tolvaptan in addition to standard therapy including diuretics improved many, though not all, HF signs and symptoms, without serious adverse events.

A study was conducted to investigate the effects of tolvaptan initiated in patients hospitalized with heart failure (HF). The Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study with Tolvaptan (EVEREST) trial indicated that tolvaptan initiated for acute treatment of patients hospitalized with HF had no effect on long-term mortality or heart failure-related morbidity.

Brain natriuretic peptide (BNP 1-32) plays an important physiologic role in cardiorenal homeostasis. Recently, it has been reported that BNP 1-32 is rapidly cleaved by the ubiquitous enzyme dipeptidyl peptidase IV to BNP 3-32, which lacks the two N[H.sub.2]-terminal amino acids of BNP 1-32. The bioactivity of BNP 3-32 in cardiorenal regulation is unknown. We hypothesized that BNP 3-32 has reduced vasodilating and natriuretic bioactivity compared with BNP 1-32 in vivo. Synthetic human BNP 3-32 and BNP 1-32 were administered to eight anesthetized normal canines. After baseline measurements, BNP 1-32 at 30 ng * [kg-.sup.-1] * [min.sup.-1] was administered, followed by a washout, a postinfusion clearance, and a clearance with an equimolar dose of BNP 3-32. In four studies, the sequence of BNP 1-32 and BNP 3-32 infusion was reversed. Peptides were compared by analyzing the changes from the respective preinfusion clearance to the respective infusion clearance. * P < 0.05 between peptides. BNP 3-32, unlike BNP 1-32, did not decrease mean arterial pressure (0 [+ or -] 1 vs. -7 [+ or -] 2 * mmHg, respectively) and did not increase renal blood flow (+12 [+ or ] 10 vs. +52 [+ or -] 10 * ml/min). Effects on heart rate and cardiac output were similar. Urinary sodium excretion increased 128 [+ or -] 18 [micro]eq/min with BNP 3-32 and 338 [+ or -] 40 * [micro]eq/min with BNP 1-32. Urine flow increased 1.1 [+ or -] 0.2 ml/min with BNP 3-32 and 2.8 [+ or -] 0.4 * ml/min with BNP 1-32. Plasma BNP immunoreactivity was lower with BNP 3-32, suggesting accelerated degradation. In this study, BNP 3-32 showed reduced natriuresis and diuresis and a lack of vasodilating actions compared with BNP 1-32. hormone; enzymatic degradation product; cardiorenal regulation; BNP 3-32

We evaluated relationships among two circulating molecular forms of brain natriuretic peptide (BNP32 and NT-proBNP), severity of hypertension (HTN), and cardiac hypertrophy in subjects with mild, moderate, and severe HTN. We prospectively studied 78 patients (43 males; mean age 51.4 [+ or -] 11 yr) with essential HTN and 28 age- and sex-matched controls. BNP32 and NT-proBNP were measured by radioimmunoassay. In grade 1 HTN, BNP32 was not elevated and NT-proBNP was reduced (P = 0.030) compared with controls. However, log-transformed values of BNP32 and NT-proBNP were both increased with severity of HTN from grade 1 to 3 (P natriuretic peptide; brain natriuretic peptide; amino-terminal pro-brain natriuretic peptide; left ventricular hypertrophy

Diuretics are frequently required to treat fluid retention in patients with congestive heart failure (CHF). Unfortunately, they can lead to a decline in renal function, electrolyte depletion, and neurohumoral activation. Arginine vasopressin (AVP) promotes renal water reabsorption via the [V.sub.2] receptor, and its levels are increased in CHF. This study was designed to assess the effects of a single oral dose of tolvaptan, a selective [V.sub.2]-receptor blocker, in the absence of other medications, on renal function in human CHF and to compare this to the effects of a single oral dose of furosemide. We hypothesized that [V.sub.2]-receptor antagonism would yield a diuresis comparable to furosemide but would not adversely affect renal hemodynamics, plasma electrolyte concentration, or neurohumoral activation in stable human CHF. Renal and neurohumoral effects of tolvaptan and furosemide were assessed in an open-label, randomized, placebo-controlled crossover study in 14 patients with NYHA II-III CHF. Patients received placebo or 30 mg of tolvaptan on day 1 and were crossed over to the other medication on clay 3. On day 5, all subjects received 80 mg of furosemide. Tolvaptan and furosemide induced similar diuretic responses. Unlike tolvaptan, furosemide increased urinary sodium and potassium excretion and decreased renal blood flow. Tolvaptan, furosemide, and placebo did not differ with respect to mean arterial pressure, glomerular filtration rate, or serum sodium and potassium. We conclude that tolvaptan is an effective aquaretic with no adverse effects on renal hemodynamics or serum electrolytes in patients with mild to moderate heart failure. congestive heart failure; [V.sub.2]-receptor antagonism; aquaretics

C-terminal brain (B-type) natriuretic peptide (BNP)-32 is a widely used clinical biomarker for the diagnosis, prognosis, and treatment of heart failure (HF). The 32-aa peptide is synthesized primarily in the atrial and ventricular myocardium and constitutes the mature biologically active form of immature BNP (pro-BNP). There has been mounting evidence that suggests BNP circulates in different structural forms that impact HF diagnosis and in vivo activity. Herein, we have developed and used an immunoaffinity purification assay to isolate endogenous BNP-32 from New York Heart Association class IV patient plasma for subsequent analysis by nano-liquid chromatography (LC) electrospray ionization Fourier transform ion cyclotron resonance (FT-ICR) MS. We have introduced stable isotopelabeled BNP-32 to the assayed plasma to enable quantification of endogenous levels of BNP-32. Unlike the chemically nonspecific point-of-care tests (POCTs) and RIAs used worldwide to quantify BNP-32 from plasma, FT-ICR-MS (unprecedented mass measurement accuracy) coupled with LC (retention time) affords extraordinary molecular specificity, and when combined with the use of internal standards is able to confidently identify and quantify BNP-32. The significance of this work is despite exceedingly high circulating levels of BNP-32 in the New York Heart Association class IV patients as determined by POCTs (>290 fmol/ml) nano-LC-electrospray ionization-FT-ICR-MS data did not reveal any endogenous BNP-32. These results provide molecularly specific evidence for the absence of circulating BNP-32 in advanced-stage HF patients and suggest the existence of altered forms of BNP that are contributing to the POCT values. biomarkers | electrospray ionization | Fourier transform-ion cyclotron resonance MS | immunoaffinity purification | targeted proteomics

Atrial (ANP) and brain (BNP) natriuretic peptides are hormones of myocardial cell origin. These hormones bind to the natriuretic peptide A receptor (NPRA) throughout the body, stimulating cGMP production and playing a key role in blood pressure control. Because NPRA receptors are present on cardiomyocytes, we hypothesized that natriuretic peptides may have direct autocrine or paracrine effects on cardiomyocytes or adjacent cardiac cells. Because both natriuretic peptides and NPRA gene expression are upregulated in states of pressure overload, we speculated that the effects of the natriuretic peptides on cardiac structure and function would be most apparent after pressure overload. To attenuate cardiomyocyte NPRA activity, transgenic mice with cardiac specific expression of a dominant-negative (DN-NPRA) mutation (HCAT D 893A) in the NPRA receptor were created. Cardiac structure and function were assessed (avertin anesthesia) in the absence and presence of pressure overload produced by suprarenal aortic banding. In the absence of pressure overload, basal and BNP-stimulated guanylyl cyclase activity assessed in cardiac membrane fractions was reduced. However, systolic blood pressure, myocardial cGMP, log plasma ANP levels, and ventricular structure and function were similar in wild-type (WT-NPRA) and DN-NPRA mice. In the presence of pressure overload, myocardial cGMP levels were reduced, and ventricular hypertrophy, fibrosis, filling pressures, and mortality were increased in DN-NPRA compared with WT-NPRA mice. In addition to their hormonal effects, endogenous natriuretic peptides exert physiologically relevant autocrine and paracrine effects via cardiomyocyte NPRA receptors to modulate cardiac hypertrophy and fibrosis in response to pressure overload. natriuretic peptides; diastole; hypertrophy; fibrosis

A hallmark of overt congestive heart failure (CHF) is attenuated cGMP production by endogenous atrial natriuretic peptide (ANP) with renal resistance to ANP. ANP and brain natriuretic peptides (BNP) are of myocardial origin, whereas urodilatin (Uro) is thought to be derived from kidney. All three peptides are agonists to the natriuretic peptide-A receptor. Our objective was to compare the cardiorenal and humoral actions of ANP, BNP, and Uro in experimental overt CHF. We determined cardiorenal and humoral actions of 90 min of intravenous equimolar infusion of ANP, BNP, and Uro (2 and 10 pmol x [kg.sup.-1] x [min.sup.-1]) in three separate groups of anesthetized dogs with rapid ventricular pacing-induced overt CHF (240 beats/rain for 10 days). BNP resulted in increases in urinary sodium excretion ([U.sub.Na],V) (2.2 [+ or -] 0.7 to 164 [+ or -] 76 [micro]eq/min, P < 0.05) and glomerular filtration rate (GFR) (27 [+ or -] 4 to 52 [+ or -] 11 ml/min, P < 0.05) that were greater than those with Uro (P < 0.05), whereas ANP did not result in increases in [U.sub.Na]V or GFR. Increases in plasma cGMP (25 [+ or -] 2 to 38 [+ or -] 2 pmol/ml, P < 0.05) and urinary cGMP excretion with BNP (1,618 [+ or -] 151 to 6,124 [+ or -] 995 pmol/min, P < 0.05) were similar to those with Uro; however, there was no change with ANP. Cardiac filling pressures were reduced in all three groups. These studies also support the conclusion that in experimental overt CHF, renal resistance to natriuretic peptides in increasing rank order is BNP < Uro < ANP. kidney; hormone; cardiac hemodynamics

The goal of the study was to define the effect of chronic unloading of the normal heart on atrial endocrine function with a focus on brain natriuretic peptide (BNP), specifically addressing the role of load and neurohumoral stimulation. Although produced primarily by atrial myocardium in the normal heart, controversy persists with regard to load-dependent vs. neurohumoral mechanisms controlling atrial BNP synthesis and storage. We used a unique canine model of chronic unloading of the heart produced by thoracic inferior vena caval constriction (TIVCC), which also resulted in activation of plasma endothelin (ET-I), ANG II, and norepinephrine (NE), known activators of BNP synthesis, compared with sham. TIVCC was produced by banding of the inferior vena cava for 10 days (n - 6), whereas in control (n = 5) the band was not constricted (sham). In a third group (n = 7), the band was released on day 11, thus acutely reloading the heart. Chronic TIVCC decreased cardiac output and right atrial pressure with a decrease in atrial mass index consistent with atrial atrophy. Atrial BNP mRNA decreased compared with sham. Immunoelectron microscopy revealed an increase in BNP in atrial granules consistent with increased storage. Acute reloading increased cardiac filling pressures and resulted in an increase in plasma BNP. We conclude that chronic unloading of the normal heart results in atrial atrophic remodeling and in suppression of atrial BNP mRNA despite intense stimulation by ET, ANG II, and NE, underscoring the primacy of load in the control of atrial endocrine function and structure. atria: myocardial load: brain natriuretic peptide

Gene transfer of a novel vasoactive natriuretic peptide stimulates cGMP and lowers blood pressure in mice. Am J Physiol Heart Circ Physiol 286: H2213-H2218, 2004. First published February 12, 2004; 10.1152/ajpheart.00465.2003.--Dendroaspis natriuretic peptide (DNP) is a recently described peptide produced by Dendroaspis angusticeps with structural and functional similarities to mammalian natriuretic peptides. These similarities suggest a potential role for DNP in cardiovascular therapeutics. To determine the physiological effects of chronic delivery of DNP, a gene transfer approach using first generation adenoviral vectors was utilized. Although the gene for DNP has not been cloned in any species, the peptide sequence in the snake is known. Preferred mammalian codons for snake DNP were cloned downstream of either the leader sequence (referred to as pBDNP-1) or prepropeptide sequence of human brain natriuretic peptide (BNP) cDNA (referred to as pBDNP-2). Transfections with pBDNP-1 or pBDNP-2 resulted in expected forms of chimeric DNP (cDNP) in cell lysates and conditioned media. Functional studies demonstrated the ability of both forms of cDNP within conditioned media to stimulate cGMP production in human vascular smooth muscle cells (hVSMC). Expressed cDNP inhibited hVSMC proliferation and stimulated vasorelaxation in a similar fashion. To investigate the chronic physiological effects of administration of cDNP, an adenoviral vector expressing cDNP (Ad-BDNP) was generated. Intravenous delivery of Ad-BDNP in mice resulted in dose-dependent systemic expression of cDNP. The highest level of expression was associated with consistent elevation of its presumed second messenger (cGMP) for 21 days but with transient lowering of systolic blood pressure in normotensive mice. This study demonstrates the biological features of the expression of the xenogenic peptide DNP. dendroaspis natriuretic peptide; adenoviral; gene delivery

Although effective in relieving symptoms of edema in congestive heart failure (CHF), diuretic-induced natriuresis may be associated with reductions in glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), which subsequently may reduce the duration of natriuresis. Moreover, recent studies have reported that the preservation of GFR is an important predictor of survival in human CHF. We hypothesized that the acute detrimental renal hemodynamic and tubular responses to furosemide in symptomatic human CHF will be attenuated by A[T.sub.1] receptor blockade with losartan. We defined the renal hemodynamic and tubular actions and aldosterone responses to furosemide (40 mg, orally) in the presence of acute A[T.sub.1] receptor antagonism (losartan, MSD, 50 mg orally) vs. placebo in 10 subjects with CHF (New York Heart Association II-III) in a double-blind, placebo-controlled crossover study. Furosemide with placebo increased sodium excretion and reduced ERPF and GFR (P < 0.05 vs. baseline). After 4 h, sodium excretion compared with baseline was decreased (P < 0.05). In contrast, furosemide with losartan resulted in a greater increase in sodium excretion but without reductions in ERPF and GFR (P < 0.05 vs. placebo). After 4 h, sodium excretion was greater compared with the placebo group. Importantly, plasma aldosterone tended to increase in the placebo group, whereas it was decreased (P < 0.05 vs. baseline) only in the losartan group. These studies underscore the pathophysiological role of the A[T.sub.1] receptor in mediating detrimental renal and adrenal properties of diuretics in human CHF. A[T.sub.1] receptor antagonism preserves GFR and renal blood flow and enhances sodium excretion during acute diuretic therapy in addition to inhibiting aldosterone secretion. These findings support the use of A[T.sub.1] receptor blockade for human CHF requiring acute diuretics to improve renal hemodynamic and tubular function and to suppress aldosterone. kidney; congestive heart failure; aldosterone; glomerular filtration rate

Many middle-aged and elderly Americans may have mild heart failure but no symptoms. In addition, many may have a form of heart failure called diastolic heart failure. In this form of heart failure, the heart pumps enough blood but does not relax sufficiently between contractions. In a study of 2,042 people 45 years old and older, about six percent had asymptomatic diastolic heart failure and six percent had asymptomatic systolic heart failure. Only half of these people had been diagnosed as having heart failure.

Background: Aldosterone is a critical pathological driver for cardiac and renal diseases. We recently discovered that mutant atrial natriuretic peptide (MANP), a novel atrial natriuretic peptide (ANP) analog, possessed more potent aldosterone inhibitory action than ANP in vivo. MANP and natriuretic peptide (NP)-augmenting therapy sacubitril/valsartan are under investigations for human hypertension treatment. Understanding the elusive mechanism of aldosterone inhibition by NPs remains to be a priority. Conflicting results were reported on the roles of the pGC-A (particulate guanylyl cyclase A receptor) and NP clearance receptor in aldosterone inhibition. Furthermore, the function of PKG (protein kinase G) and PDEs (phosphodiesterases) on aldosterone regulation are not clear.Methods: In the present study, we investigated the molecular mechanism of aldosterone regulation in a human adrenocortical cell line H295R and in mice.Results: We first provided evidence to show that pGC-A, not NP clearance receptor, mediates aldosterone inhibition. Next, we confirmed that MANP inhibits aldosterone via PDE2 (phosphodiesterase 2) not PKG, with specific agonists, antagonists, siRNA silencing, and fluorescence resonance energy transfer experiments. Further, the inhibitory effect is mediated by a reduction of intracellular Ca2+ levels. We then illustrated that MANP directly reduces aldosterone synthase CYP11B2 (cytochrome p450 family 11 subfamily b member 2) expression via PDE2. Last, in PDE2 knockout mice, consistent with in vitro findings, embryonic adrenal CYP11B2 is markedly increased.Conclusions: Our results innovatively explore and expand the NP/pGC-A/3',5', cyclic guanosine monophosphate (cGMP)/PDE2 pathway for aldosterone inhibition by MANP in vitro and in vivo. In addition, our data also support the development of MANP as a novel ANP analog drug for aldosterone excess treatment. [ABSTRACT FROM AUTHOR]

C-type natriuretic peptide (CNP) possesses well-established cardiovascular properties. Although present in the mammalian kidney, CNP production in human kidney and its modulation in human renal disease remain less defined. We investigated the presence of CNP in normal human kidney and in patients with nephrotic syndrome (NS). We also addressed whether or not a low-protein diet (LPD) alters plasma CNP and urinary CNP excretion in NS. In situ hybridization studies demonstrated CNP mRNA expression in tubular cells and glomeruli of normal human kidneys. CNP immunoreactivity was positive in proximal, distal, and medullary collecting duct tubular cells in both controls and patients with NS. The ratios of plasma CNP and urinary CNP to creatinine were significantly higher in patients with NS compared with controls. Urinary CNP, but not plasma CNP, was significantly lowered in patients with NS after an LPD. Similarly, the ratios of urinary protein to creatinine and urinary albumin to creatinine, but not urinary guanosine 3',5'-cyclic monophosphate to creatinine, decreased significantly with an LPD. These data confirm and extend previous reports and demonstrate for the first time the presence of CNP in human kidney with NS. We also report increased plasma CNP concentration and urinary CNP excretion in NS patients and a significant reduction of CNP excretion with an LPD. Our findings demonstrate that CNP metabolism is altered in patients with NS and support the hypothesis that activation of renal CNP can be partially offset by an LPD. These results underscore that the beneficial effect of an LPD on protein excretion is paralleled by a substantial reduction in intrarenal CNP release. low protein diet; urinary C-type natriuretic peptide; immunohistochemistry; in situ hybridization

Dendroaspis natriuretic peptide (DNP) is a recently discovered peptide with structural similarity to known natriuretic peptides. DNP has been shown to possess potent renal actions. Our objectives were to define the acute hemodynamic actions of DNP in normal anesthetized dogs and the acute effects of DNP on left ventricular (LV) function in conscious chronically instrumented dogs. In anesthetized dogs, DNP, but not placebo, decreased mean arterial pressure (141 [+ or -] 6 to 109 [+ or -] 7 mmHg, P < 0.05) and pulmonary capillary wedge pressure (5.8 [+ or -] 0.3 to 3.4 [+ or -] 0.2 mmHg, P < 0.05). Cardiac output decreased and systemic vascular resistance increased with DNP and placebo. DNP-like immunoreactivity and guanosine 3',5'-cyclic monophosphate concentration increased without changes in other natriuretic peptides. In conscious dogs, DNP decreased LV end-systolic pressure (120 [+ or -] 7 to 102 [+ or -] 6 mmHg, P < 0.05) and volume (32 [+ or -] 6 to 28 [+ or -] 6 ml, P < 0.05) and LV end-diastolic volume (38 [+ or -] 5 to 31 [+ or -] 4 ml, P < 0.05) but not arterial elastance. LV end-systolic elastance increased (6.1 [+ or -] 0.7 to 7.4 [+ or -] 0.6 mmHg/ml, P < 0.05), and Tau decreased (31 [+ or -] 2 to 27 [+ or -] 1 ms, P < 0.05). The effects on hemodynamics, LV function, and second messenger generation suggest synthetic DNP may have a role as a cardiac unloading and lusitropic peptide. natriuretic peptides; systolic function; diastolic function

Background: cGMP MANP (M-atrial natriuretic peptide) is a best-in-class activator of the pGC-A (particulate guanylyl cyclase A) receptor. Furosemide increases the effectiveness of antihypertensive agents, but activates renin-angiotensin-aldosterone system. We aimed to investigate for the first time cardiorenal and neurohumoral actions of MANP in a genetic model of hypertension in spontaneously hypertensive rats. We also assessed how MANP would potentiate the blood pressure (BP)-lowering actions of furosemide while reducing the production of aldosterone.Methods: Spontaneously hypertensive rats (N=60) were randomized in vehicle, MANP, furosemide, or MANP+furosemide groups. Furosemide (1, 5, 10 mg/kg) was given as a single bolus which in MANP+furosemide groups was followed by a 60-minute infusion of MANP.Results: BP was reduced in MANP300 (300 pmol/[kg·min]) and MANP600 (600 pmol/[kg·min]) groups (P<0.05) and was accompanied by significant increase in plasma cyclic guanosine monophosphate. Furosemide alone reduced BP but less compared with MANP with no change in plasma cyclic guanosine monophosphate. MANP+furosemide resulted in the greatest BP reduction and significant increase in plasma cyclic guanosine monophosphate in Fs5+MANP300, Fs10+MANP300, and Fs10+MANP600. Plasma aldosterone increased in furosemide groups, which was significantly attenuated in MANP+furosemide groups. Natriuresis and diuresis increased in all treated groups (P<0.05) with no significant differences between furosemide and furosemide+MANP. In vitro, MANP increased cyclic guanosine monophosphate level in human vascular cells.Conclusions: We provide novel evidence that MANP potentiates the BP-lowering actions of furosemide, suppresses the activation of renin-angiotensin-aldosterone system, and preserves renal function. These data are highly relevant to clinical needs in the treatment of hypertension and heart failure. [ABSTRACT FROM AUTHOR]

Left atrial and left ventricular (LV) gene expression and tissue concentration including circulating brain natriuretic peptide (BNP) were determined during the evolution of rapid ventricular pacing-induced congestive heart failure (CHF) in the dog. Early LV dysfunction after 10 days of pacing was characterized by impaired LV function but maintained arterial pressure. Overt CHF after 38 days of pacing was characterized by further impaired LV function and decreased systemic arterial pressure.

Research was conducted to study the functions of endothelin-B (ET-B) receptor activation in vivo that results in increases in plasma ET-1 and systemic and pulmonary vasoconstriction and reductions in CO and SV(sub O2) in dogs. Blood for ET-1 analysis was collected into EDTA tubes while the animals were maintained on a normal sodium diet. Results indicated that cardiovascular responses were present only at pharmacological concentrations of S6c. They also showed that ual ET-A/ET-b receptor antagonism attenuates the cardiovascular actions of the ET-B receptor.

The functional role of the endogenous natriuretic peptide system in the modulation of ventricular and coronary vascular function in congestive heart failure (CHF) was investigated in anesthetized CHF dogs. Results have shown that the intracardiac natriuretic peptide system was activated in the presence of heart failure. It was further indicated that the endogenous natriuretic peptide system has an autocrine-paracrine role to mediate left entricular and coronary vascular function in CHF.

A study was conducted on the immunohistochemical localizations and renal, urinary, cardiac and plasma tissue concentrations of adrenomedullin in dogs. Adrenomedullin was compared in dogs suffering from rapid ventricular pacing-induced congestive heart failure and normal dogs. Results reveal that plasma adrenomedullin levels rise in experimental heart rate failure and that activation of ventricular and renal adrenomedullin occurs during congestive heart failure progression.

The role of brain natriuretic peptides on the pathogenesis of acute heart failure (AHF) was analyzed in anesthetized dogs after rapid left ventricular pacing (RLVP). Analysis of hemodynamic and renal responses during RLVP-induced AHF in anesthetized dogs indicated the role of elevated atrial filling pressures in increasing the levels of circulating atrial natriuretic peptide. However, BNP was not affected by cardiac filling pressures.

The role of the prostaglandin system and renal nerve activity in adrenomedullin (ADM)-mediated natriuresis was analyzed in the denervated kidney of anesthetized mongrel dogs. Administration of ADM in the denervated kidney of anesthetized mongrel dogs increased urinary sodium secretion and renal blood flow. The natriuretic actions of ADM were mediated by the renal nerves and the prostaglandin system. Furthermore, inhibition of prostaglandin activity attenuated ADM-induced natriuresis.

The effects of congestive heart failure on the function and mass of the left ventricle (LV) were analyzed by utilizing atrial natriuretic peptide (ANP) immunoreactivity in dog ventricular myocardium. Tachycardia-induced cardiomyopathy caused LV hypertrophy due to increased LV mass and ANP levels. Furthermore, progressively increasing levels of rapid ventricular pacing in dogs ventricular myocardium increased LV diameter, filling pressures and circulating ANP.

The mechanism by which the natriuretic peptide (CNP) promotes smooth muscle relaxation was investigated using femoral veins isolated from mongrel dogs. The veins were treated with endothelin, phenylephrine, and metabolic inhibitors prior to exposure to CNP. KCl and endothelin-1 attenuated the response to CNP, but the metabolic inhibitors inhibited relaxations to CNP. These results indicate that response to CNP is mediated by activation of potassium channels.

A study of the importance of natriuretic peptide C receptor (NPR-C) receptor in the regulation of C-type natriuretic peptide (CNP) total and regional clearance. Pulmonary circulation is a probable site for CNP secretion while CNP is cleared via renal and peripheral circulation sites. Specific cardiovascular CNP actions are mediated by NPR-C blockade.

Adrenomedullin (ADM) has been located in glomeruli, cortical distal tubules and medullary collecting duct cells of the kidney by immunohistochemical analysis. Being a natriuretic peptide, ADM has a major role in the regulation of sodium excretion. Due to this, intrarenal infusion of ADM results in diuretic and natriuretic response. This is marked by a complementary increase in glomerular filtration rate and fractional sodium excretion and a decrease in distal tubular sodium reabsorption.

Study of endothelin (ET) subreceptors reveals that endothelin-A subreceptor (ET(A)) is associated with renal vasoconstriction and ET(B) is involved in diuretic response during exogenous ET. The endothelin is a powerful vasoconstrictor peptide of endothelial origin, which causes diuresis and renal vasoconstriction. The study indicates that endothelin at very low doses reduces the proximal tubular reabsorption of sodium.

A study of the secretion and pressure of atrial natriuretic peptide (ANP) immunoreactivity in vascular endothelial cells using radioimmunoassay and immunohistochemical staining reveals that ANP is present in vascular endothelium and that it acts as a paracrine and autocrine regulator of vascular growth and tone modulation. Endothelin-1 (ET-1) and ANP exhibit a differential distribution, with the cell culture media containing higher levels of ET-1 and the cell extracts containing higher ANP levels.