Atriopeptin: a cardiac hormone intimately involved in fluid, electrolyte, and blood-pressure homeostasis

How should we assess the cardiovascular system in patients presenting with bothersome nocturia? ICI-RS 2023

AIMS

The link between nocturia and cardiovascular disease (CVD) is frequently discussed in literature, yet the precise nature of this relationship remains poorly characterized. The existing literature was reviewed in order to address issues concerning the origin, diagnosis, management, and implications of the co-occurrence of CVD and nocturia.

METHODS

This review summarizes literature and recommendations regarding the link between CVD and nocturia discussed during a think-tank meeting held at the 2023 International Consultation on Incontinence-Research Society.

RESULTS

Cardiovascular disorders are often underestimated contributors to nocturia, with various potential mechanisms influencing nighttime urination, such as impact on fluid retention, atrial natriuretic peptide, and glomerular filtration rate. The redistribution of fluid from leg edema in supine position can lead nocturnal polyuria (NP). Additionally, sleep disturbances due to nocturia in itself may lead to CVD through an increase in blood pressure, insulin resistance, and inflammation. Disrupted circadian rhythms (e.g., in sleep pattern and urine production) were identified as critical factors in most etiologies of nocturia, and their contribution is deemed imperative in future research and treatment approaches, particularly in the aging population. NP can be detected through a simple bladder diary and can even be used to distinguish cardiac from noncardiac causes of nocturia. For the treatment of NP, desmopressin can be effective in select patients, however, caution and close monitoring is warranted for those with CVD due to increased risk of side effects.

CONCLUSIONS

Gaps were identified in the available evidence and clear cut recommendations were put forth for future research. It is essential to gain a deeper understanding of the mechanisms linking nocturia and CVD to develop optimal management strategies.

Nanoparticles-induced potential toxicity on human health: Applications, toxicity mechanisms, and evaluation models

Nanoparticles (NPs) have become one of the most popular objects of scientific study during the past decades. However, despite wealth of study reports, still there is a gap, particularly in health toxicology studies, underlying mechanisms, and related evaluation models to deeply understanding the NPs risk effects. In this review, we first present a comprehensive landscape of the applications of NPs on health, especially addressing the role of NPs in medical diagnosis, therapy. Then, the toxicity of NPs on health systems is introduced. We describe in detail the effects of NPs on various systems, including respiratory, nervous, endocrine, immune, and reproductive systems, and the carcinogenicity of NPs. Furthermore, we unravels the underlying mechanisms of NPs including ROS accumulation, mitochondrial damage, inflammatory reaction, apoptosis, DNA damage, cell cycle, and epigenetic regulation. In addition, the classical study models such as cell lines and mice and the emerging models such as 3D organoids used for evaluating the toxicity or scientific study are both introduced. Overall, this review presents a critical summary and evaluation of the state of understanding of NPs, giving readers more better understanding of the NPs toxicology to remedy key gaps in knowledge and techniques.

Nocturia independently predicts left ventricular hypertrophy and left atrial enlargement among patients with cardiac symptoms

Nocturia can be caused by urological disorders and systemic diseases, including heart diseases. We aimed to investigate the relationship between nocturia and structural abnormalities on echocardiography. Adult patients who underwent echocardiography for cardiac symptoms or heart murmur or had a history of structural heart disease were included. The voiding times during sleep hours were collected prospectively. Univariate and multivariate analyses were performed to evaluate the predictive value of bothersome nocturia (nocturia ≥ 2) on echocardiographic abnormalities. Of 299 patients, 182 (60.9%) reported bothersome nocturia. In patients aged ≥ 65 years, hypertension and left atrial enlargement (LAE) were associated with higher occurrences of bothersome nocturia. On multivariate analysis, bothersome nocturia was a predictive factor of LAE (odds ratio [OR] 2.453, 95% confidence interval [CI] 1.363–4.416, p = 0.003). Moreover, bothersome nocturia could predict both LAE and left ventricular hypertrophy (LVH) (OR 2.285, 95% CI 1.151–4.536, p = 0.018; OR 2.056, 95% CI 1.025–4.124, p = 0.043) in the elderly. Older age, hypertension, and LAE were risk factors for bothersome nocturia. Moreover, bothersome nocturia was predictive of LAE and LVH in the elderly. Patients with bothersome nocturia without other significant lower urinary tract symptoms should be referred to cardiologists.

Effects and safety of natriuretic peptides as treatment of cirrhotic ascites: A systematic review and meta-analysis

BACKGROUND

Natriuretic peptides are involved in the cascade of pathophysiological events occurring in liver cirrhosis, counterbalancing vasoconstriction and anti-natriuretic factors. The effects of natriuretic peptides as treatment of cirrhotic ascites have been investigated only in small studies, and definitive results are lacking.

AIM

To examine the effects and safety of natriuretic peptides in cirrhosis patients with ascites.

METHODS

We searched MEDLINE, Web of Science, Scopus, Cochrane Library and Embase for all available studies applying intravenous administration of any natriuretic peptide to patients suffering from cirrhotic ascites. Inclusion was not limited by treatment duration or dose, or by follow-up duration. Both randomised controlled trials and non-randomised studies were eligible for inclusion. The primary outcome was change in renal sodium excretion. Secondary outcomes included safety measures and changes in renal water excretion, plasma aldosterone concentration, and plasma renin activity.

RESULTS

Twenty-two studies were included. Atrial natriuretic peptide (ANP) was the only intensively studied treatment. Sodium excretion increased in response to continuous ANP infusion and was more pronounced when infusion rates of > 30 ng/kg/min were administered compared with ≤ 30 ng/kg/min (P < 0.01). Moreover, natriuresis was significantly higher in study subgroups with mild/moderate ascites compared with moderate/severe and refractory ascites (P < 0.01). ANP infusions increased renal water excretion, although without reaching a statistically significant dose-response gradient. Plasma aldosterone concentration and plasma renin activity were significantly lower at baseline in study subgroups achieving a negative sodium balance in response to an ANP administration compared with treatment non-responders (P < 0.01). Blood pressure decreases occurred less frequently when ANP doses ≤ 30 ng/kg/min were applied. The quality of evidence for a natriuretic response to ANP was low, mainly due to small sample sizes and considerable between-study heterogeneity. Data were sparse for the other natriuretic peptides; B-type natriuretic peptide and urodilatin.

CONCLUSION

Intravenous ANP infusions increase sodium excretion in patients with cirrhotic ascites. Continuous infusion rates > 30 ng/kg/min are the most effective. However, safety increases with infusion rates ≤ 30 ng/kg/min.

Human Atrial Natriuretic Peptide in Cold Storage of Donation After Circulatory Death Rat Livers: An Old but New Agent for Protecting Vascular Endothelia?

BACKGROUND

Current critical shortage of donor organs has increased the use of donation after circulatory death (DCD) livers for transplantation, despite higher risk for primary nonfunction or ischemic cholangiopathy. Human atrial natriuretic peptide (hANP) is a cardiovascular hormone that possesses protective action to vascular endothelia. We aimed to clarify the therapeutic potential of hANP in cold storage of DCD livers.

METHODS

Male Wistar rats were exposed to 30-minute warm ischemia in situ. Livers were then retrieved and cold-preserved for 6 hours with or without hANP supplementation. Functional and morphological integrity of the livers was evaluated by oxygenated ex vivo reperfusion at 37°C.

RESULTS

hANP supplementation resulted in significant reduction of portal venous pressure (12.2 ± 0.5 versus 22.5 ± 3.5 mm Hg, P < 0.001). As underlying mechanisms, hANP supplementation significantly increased tissue adenosine concentration (P = 0.008), resulting in significant upregulation of endothelial nitric oxide synthase and significant downregulation of endothelin-1 (P = 0.01 and P = 0.004 vs. the controls, respectively). Consequently, hANP significantly decreased transaminase release (P < 0.001) and increased bile production (96.2 ± 18.2 versus 36.2 ± 15.2 μL/g-liver/h, P < 0.001). Morphologically, hepatocytes and sinusoidal endothelia were both better maintained by hANP (P = 0.021). Electron microscopy also revealed that sinusoidal ultrastructures and microvilli formation in bile canaliculi were both better preserved by hANP supplementation. Silver staining also demonstrated that hANP significantly preserved reticulin fibers in Disse space (P = 0.017), representing significant protection of sinusoidal frameworks/architectures.

CONCLUSIONS

Supplementation of hANP during cold storage significantly attenuated cold ischemia/warm reperfusion injury of DCD livers.

Changes in Atrial Natriuretic Peptide Concentration at Femoral Arteriography in Man

The changes in plasma concentrations of atrial natriuretic peptide were investigated in 10 patients who were examined for peripheral vessel disease by aorto-femoral angiography. All patients received 6×40 ml contrast medium (iohexol, 300 mg I/ml) plus an initial test dose of 15 ml, resulting in a total mean dose of 255 ml injected into the abdominal aorta. The contrast medium injections produced a significant increase in plasma atrial natriuretic peptide concentration (p<0.02). Furthermore a significant decrease was seen in systolic blood pressure (p<0.04). It is concluded that the plasma concentration of atrial natriuretic peptide increases after intraarterial injection of contrast medium, and that atrial natriuretic peptide might play a role in the hemodynamic changes seen after intravascular injections of contrast medium.

Systemic and Pulmonary Haemodynamic Effects of Intravenous Infusion of Non-Ionic Isoosmolar Dimeric Contrast Media

The systemic and pulmonary haemodynamic effects of i.v. infusion (1 ml/s) of high doses (4 ml/kg) of 2 non-ionic, isoosmolar dimeric contrast media (CM) were investigated in 17 female pigs. The 2 CM were iodixanol and iotrolan. Both CM induced a significant increase of the following parameters: mean arterial, mean right atrial, mean pulmonary arterial, mean pulmonary arterial occlusion pressure, cardiac output, stroke volume, and diuresis. The plasma concentration of atrial natriuretic peptide was significantly increased following infusion of the 2 CM. A significant decrease was seen in the systemic and pulmonary vascular resistance.

Atrial natriuretic factor: is it responsible for hyponatremia and natriuresis in neurosurgery?

Objective

To evaluate the presence of hyponatremia and natriuresis and their association with atrial natriuretic factor in neurosurgery patients.

Methods

The study included 30 patients who had been submitted to intracranial tumor resection and cerebral aneurism clipping. Both plasma and urinary sodium and plasma atrial natriuretic factor were measured during the preoperative and postoperative time periods.

Results

Hyponatremia was present in 63.33% of the patients, particularly on the first postoperative day. Natriuresis was present in 93.33% of the patients, particularly on the second postoperative day. Plasma atrial natriuretic factor was increased in 92.60% of the patients in at least one of the postoperative days; however, there was no statistically significant association between the atrial natriuretic factor and plasma sodium and between the atrial natriuretic factor and urinary sodium.

Conclusion

Hyponatremia and natriuresis were present in most patients after neurosurgery; however, the atrial natriuretic factor cannot be considered to be directly responsible for these alterations in neurosurgery patients. Other natriuretic factors are likely to be involved.

Are endogenous cardenolides controlled by atrial natriuretic peptide

Endogenous cardenolides are digoxin-like substances and ouabain-like substances that have been implicated in the pathogenesis of hypertension and mood disorders in clinical and pre-clinical studies. Regulatory signals for endogenous cardenolides are still unknown. These endogenous compounds are believed to be produced by the adrenal gland in the periphery and the hypothalamus in the central nervous system, and constitute part of an hormonal axis that may regulate the catalytic activity of the α subunit of Na(+)/K(+)-ATPase. A review of literature suggests that there is great overlap in physiological environments that are associated with either elevations or reductions in the levels of atrial natriuretic peptide (ANP) and endogenous cardenolides. This suggests that these two factors may share a common regulatory signal or perhaps that ANP may be involved in the regulation of endogenous cardenolides.

Association of CVD candidate gene polymorphisms with ischemic stroke and cerebral hemorrhage in Chinese individuals

BACKGROUND

Contribution of cardiovascular disease related genetic risk factors for stroke are not clearly defined. We performed a genetic association study to assess the association of 56 previously characterized gene variants in 34 candidate genes from cardiovascular disease related biological pathways with ischemic stroke and cerebral hemorrhage in a Chinese population.

METHODS

There were 1280 stroke patients (1101 with ischemic stroke and 179 with cerebral hemorrhage) and 1380 controls in the study. The genotypes for 56 polymorphisms of 34 candidate genes were determined by the immobilized probe approach and the associations of gene polymorphisms with ischemic stroke and cerebral hemorrhage were performed by logistic regression under an allelic model.

RESULTS

After adjusting for age, sex, BMI and hypertension status by logistic regression analysis, we found that NPPA rs5063 was significantly associated with both ischemic stroke (odds ratio [OR] 0.69; 95% confidence interval [CI], 0.52 to 0.90; P = 0.006) and cerebral hemorrhage(OR = 0.39; 95%CI, 0.19 to 0.78; P = 0.007). In addition, MTHFR rs1801133 also was associated with cerebral hemorrhage (OR = 1.48; 95%CI, 1.16 to 1.89; P = 0.001) but not with ischemic stroke (OR = 1.08; 95%CI, 0.96 to 1.22; P = 0.210). After false discovery rate (FDR) correction, the association of NPPA rs5063 and MTHFR rs1801133 with cerebral hemorrhage remained significant.

CONCLUSIONS

The NPPA rs5063 is associated with reduced risk for cerebral hemorrhage and MTHFR rs1801133 is associated with increased risk of cerebral hemorrhage in a Chinese population.

Nanotoxicity: a growing need for study in the endocrine system

Nanomaterials (NMs) are engineered for commercial purposes such as semiconductors, building materials, cosmetics, and drug carriers, while natural nanoparticles (NPs) already exist in the environment. Due to their unique physicochemical properties, they may interact actively with biological systems. Some of these interactions might be detrimental to human health, and therefore studies on the potential 'nanotoxicity' of these materials in different organ systems are warranted. The purpose of developing the concept of nanotoxicity is to recognize and evaluate the hazards and risks of NMs and evaluate safety. This review will summarize and discuss recent reports derived from cell lines or animal models concerning the effects of NMs on, and their application in, the endocrine system of mammalian and other species. It will present an update on current studies of the effects of some typical NMs-such as metal-based NMs, carbon-based NMs, and dendrimers-on endocrine functions, in which some effects are adverse or unwanted and others are favorable or intended. Disruption of endocrine function is associated with adverse health outcomes including reproductive failure, metabolic syndrome, and some types of cancer. Further investigations are therefore required to obtain a thorough understanding of any potential risk of pathological endocrine disruption from products containing NMs. This review aims to provide impetus for further studies on the interactions of NMs with endocrine functions.

Effectiveness of human atrial natriuretic peptide supplementation in pulmonary edema patients using the pulse contour cardiac output system

PURPOSE

Atrial natriuretic peptide (ANP) has a variety of pharmacologic effects, including natriuresis, diuresis, vasodilatation, and suppression of the reninangiotensin system. A recent study showed that ANP infusion improved hypoxemia and pulmonary hypertension in a lung injury model. On the other hand, the pulse contour cardiac output (PiCCO(TM)) system (Pulsion Medical Systems, Munich, Germany) allows monitoring of the intravascular volume status and may be used to guide volume therapy in severe sepsis and critically ill patients.

MATERIALS AND METHODS

We treated 10 pulmonary edema patients without heart disease with human ANP (HANP). The patients were divided into two groups: a group with normal Intrathoracic Blood Volume (ITBV) (900-1100 mL/m(2)) (n = 6), and a group with abnormal ITBV (n = 4), as measured by the PiCCO(TM) device; the extravascular lung water (EVLW) and pulmonary vascular permeability index (PVPI) in the two groups were compared.

RESULTS

The average patient age was 63.9 +/- 14.4 years. The normal ITBV group showed significant improvement of the EVLW (before, 16.7 +/- 2.7 mL/kg; after, 10.5 +/- 3.6 mL/kg; p = 0.0020) and PVPI (before, 3.2 +/- 0.3; after, 2.1 +/- 0.7; p = 0.0214) after the treatment. The abnormal ITBV group showed no significant improvement of either the EVLW (before, 16.3 +/- 8.9 mL/kg; after, 18.8 +/- 9.6 mL/kg; p = 0.8387) or PVPI (before, 2.3 +/- 0.8; after, 2.7 +/- 1.3; p = 0.2782) after the treatment. In both groups, the EVLW and PVPI were strongly correlated with the chest X-ray findings.

CONCLUSION

We conclude that HANP supplementation may improve the EVLW and PVPI in pulmonary edema patients without heart disease with a normal ITBV. The PiCCO(TM) system seems to be a useful device for the management of pulmonary edema.

Gene expression of natriuretic peptides and their receptors type-A and-C after myocardial infarction in rats

The purpose of this study was to investigate myocardial mRNA expression of brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) in different regions of the heart at three different time points after induction of myocardial infarction (MI) in rats. Furthermore, we examined putative changes in mRNA expression of natriuretic peptide receptors (NPRs), NPR-A and NPR-C, in myocardium and peripheral organs. Substantial increase in the mRNA levels of both BNP and ANP in the infarcted as well as non-infarcted regions were observed after induction of MI. These findings were paralleled by elevated circulating concentrations of ANP, BNP and N-terminal proANP (Nt-proANP). In addition, the mRNA levels of the clearance receptor, NPR-C, were augmented in the infarcted and non-infarcted regions of the left ventricular wall (LV), while it was decreased in the kidneys and lungs 28 days post-MI. Based on these data, we propose that, in addition to increased myocardial secretion of BNP and ANP, reduced peripheral clearance by NPR-C may contribute to the observed increase in circulating plasma concentrations of the natriuretic peptides after induction of MI in rats.

A study of alpha-human atrial natriuretic peptide in normal pregnancy and in pre-eclampsia

The object of this study was to compare plasma levels of alpha-human atrial natriuretic peptide (ANP) in patients with pre-eclampsia, normal pregnant women, and healthy non-pregnant women. This was an observational study carried out at Llandough Hospital, Cardiff, Wales on 85 age-matched women divided into three groups (30 patients with pre-eclampsia, 30 healthy pregnant women in the third trimester and 25 healthy non-pregnant women). Plasma ANP concentration was measured between 14.00 and 16.00 hours, in the recumbent position using pre-extraction radioimmunoassay. The following measurements were also performed: blood urea, serum creatinine, serum uric acid and serum sodium in all study subjects and 24-hour urinary protein in pregnant women. All women were eating a normal diet. It was shown that plasma ANP levels were significantly higher in healthy pregnant women in the third trimester of pregnancy than in non-pregnant women (18.12 +/- 7.36 vs. 13.68 +/- 6.41 pmol/l, P < 0.05). This difference was also observed in pre-eclamptic women (17.6 +/- 12.06 pmol/l vs. 13.68 +/- 6.41 pmol/l, P < 0.05) but the plasma hormone levels were not significantly different from healthy pregnant women. In all pregnant women, plasma ANP level was related to the gestational age and birth weight as shown by the regression coefficient (+ 0.39,-0.26 respectively, P < 0.05). In pre-eclamptic patients, there was no relationship between the severity of hypertension, assessed by the level of systolic and diastolic blood pressure, serum uric acid level and amount of proteinuria, and log (plasma) ANP levels. There was a significant negative correlation between serum sodium level and log (plasma) ANP level in all pregnant subjects (r=- 0.51, P < 0.05). Compared with non-pregnant women, plasma ANP levels are increased during the third trimester of normal pregnancy and in pregnancies complicated by pre-eclampsia. A relationship between ANP and pre-eclampsia seems unlikely but ANP is probably involved in the regulation of sodium and water balance in normal pregnancy and in pre-eclampsia.

Atrial natriuretic peptide during human pregnancy and puerperium

In 1981 De Bold and colleagues demonstrated that when extracts of atrial tissue were given intravenously to rats a large diuresis and natriuresis occured promptly. The structure of the hormone concerned, atrial natriuretic peptide (ANP), was elucidated in 1983. Since then, ANP has received attention as a potentially important mediator in the homoeostasis of sodium and fluid volume.

Hemodynamic and humoral effects of atrial natriuretic peptide on pulmonary circulation after cardiac surgery

PURPOSE

Human atrial natriuretic peptide (h-ANP) elicits biological effects such as natriuresis, diuresis, and vasodilation, and plays a role in regulating pulmonary circulation. We conducted this clinical study to define its role and elucidate its mechanisms.

METHODS

Twelve consecutive adult patients scheduled to undergo cardiac surgery with cardiopulmonary bypass (CPB) were prospectively selected for this study. After the completion of surgery, h-ANP was infused from the right atrium through a Swan-Ganz (S-G) catheter. Blood samples for measurement of ANP and cyclic guanosine monophosphate (cGMP), the second messenger of ANP, were drawn from the pulmonary artery (PA) through the S-G catheter and from the left atrium (LA) through the left atrial pressure line, before and after the infusion of h-ANP. Hemodynamic values were measured at the same time.

RESULTS

After the h-ANP infusion, the plasma levels of ANP were significantly lower in the LA than in the PA, whereas the plasma levels of cGMP were significantly higher in the LA than in the PA. The infusion of h-ANP decreased the mean PA pressure significantly, and the systolic PA pressure remarkably.

CONCLUSION

The infusion of h-ANP after cardiac surgery stimulates the secretion of cGMP from the pulmonary vascular bed and dilates the PA, thereby decreasing the PA pressure.

Determinanten des insensiblen Flüssigkeitsverlustes

Accurate perioperative fluid balance is the basis of a targeted infusion regimen. However, neither the initial status nor perioperative changes of the fluid compartments can be reliably measured in daily routine. In particular, insensible losses are not consistently assessed, so that substitution therapy is generally empirical. The object of this paper is to communicate the scientific data on this topic. Preoperative fasting (10 h) does not per se cause intravascular hypovolemia. In adults, total basal evaporation by way of the skin and airways and of any wounds during major abdominal interventions is usually less than 1 ml/kg/h. An inconstant fluid and protein shift towards the interstitial space perioperatively seems to be associated with hypervolemia, which suggests it should be preventable. The decisive factor in this context seems to be deterioration of the endothelial glycocalyx, whose further patho-physiological impact is currently only partially known. Clinical studies have revealed a link between fluid restriction and improved outcome after major abdominal surgery.

Atrial natriuretic peptide release associated with smoke inhalation and physiological responses to thermal injury in sheep

Markedly elevated levels of plasma atrial natriuretic peptide (ANP), which exhibit potent diuretic and vasoactive properties, has been well documented in patients with acute lung injury. We examined the physiological effects of additional smoke inhalation on plasma ANP concentrations in an ovine burn model. Seventeen sheep were instrumented to receive fluid and have physiological measurements taken. The burn group (n=8) received 40% body surface area third degree burn and the burn+smoke group (n=9) received the same burn plus 48 breaths of cotton smoke insufflation. The animals were resuscitated according to the Parkland formula with Ringer's lactate in the following 72 h period. Hemodynamic, oxygenation, fluid balance, and plasma ANP levels were serially determined. The effects of smoke inhalation manifested as deteriorated oxygenation, and increased fluid accumulation after a sustained initial shock period of more than 12 h. Plasma ANP levels in the burn+smoke group showed a biphasic elevation, whereas the burn group showed no appreciable changes throughout the whole experimental period. The initial increase in plasma ANP concentrations occurred immediately after injury (from 96+/-10 at baseline to 136+/-17 pg/mL at 3h after injury); thereafter, it decreased towards baseline value, followed by a second increase in the post resuscitation period (183+/-43 pg/mL at 72 h after injury). Decreased urine output and accentuated pulmonary vascular resistance in the combined injury group was observed between the two ANP level peaks, indicating that ANP release modified physiological responses to the burn+smoke injury.

Time Course and Prognostic Value of Plasma Levels of N-Terminal Pro-Brain Natriuretic Peptide in Patients After Ischemic Stroke

BACKGROUND

The association between plasma levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) and prognostic outcomes in patients after ischemic stroke remains unknown. The present study tested the hypothesis that NT-proBNP level is noticeably increased after ischemic stroke and that elevated NT-proBNP is associated with unfavorable clinical outcomes (UFCO).

METHODS AND RESULTS

Blood samples for NT-proBNP levels were collected serially and examined with sandwich immunoassay after acute ischemic stroke in 86 consecutive patients. The NT-proBNP levels were also measured in 30 healthy control volunteers and 30 at-risk control subjects. The NT-proBNP levels were significantly higher at 4 intervals after ischemic stroke than in healthy and at-risk control subjects (all p<0.001). The NT-proBNP decreased to a significantly lower level on day 21 and to a substantially lower level on day 90. Additionally, the NT-proBNP level at any of the 4 intervals was significantly higher in patients with than in patients without UFCO (defined as combined congestive heart failure > or = class 3, acute myocardial infarction, recurrent stroke or any cause of death) (all p<0.01). Multivariate analysis demonstrated that age and NIH Stroke Scale were the 2 strongest independent predictors of increased NT-proBNP levels (all p<0.01). Furthermore, increased NT-proBNP (> or = 150 pg/ml) was the strongest independent predictor of long-term (mean follow-up: 24 months) UFCO (26 patients) (all p<0.05).

CONCLUSIONS

The NT-proBNP level was markedly elevated after acute ischemic stroke and declined substantially thereafter. An increased NT-proBNP level was strongly and independently correlated with UFCO in patients after ischemic stroke.

Variable number of tandem repeat of the 5'-flanking region of type-C human natriuretic peptide receptor gene influences blood pressure levels in obesity-associated hypertension

The gene for natriuretic peptides receptor C (NPRC), which is a candidate susceptibility gene for essential hypertension (EH) or obese hypertension, plays a key role in the regulation of plasma levels and biological effects of natriuretic peptides. The aims of the present study were to find new genetic markers in the 5'-flanking region of the NPRC gene and to assess relationships between variants and phenotypes of EH, including EH in obese patients. Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis, we discovered a novel six-nucleotide repeat polymorphism located 4 base pairs (bp) upstream of the major transcriptional initiation site. We performed association analysis of this variable number of tandem repeat (VNTR) in 242 EH patients and 212 normotensive controls (NT). Although no significant difference in overall frequency of VNTR was found between NT and EH groups, the blood pressure level of EH patients with the 5/6 genotype was significantly higher in obese subjects. This suggests that the VNTR of the 5'-flanking region of the NPRC gene influences blood pressure levels in obesity-associated hypertension.

Role of atrial natriuretic peptide in pulmonary permeability and vasoregulation in ovine sepsis

OBJECTIVE

Atrial natriuretic peptide is regarded as an important regulator of pulmonary vasomotor tone and permeability. This study investigated the role of atrial natriuretic peptide in sepsis-associated pulmonary pathophysiology.

DESIGN

Prospective experimental investigation.

SETTING

Laboratory at a university hospital.

SUBJECTS

Twelve awake, chronically instrumented sheep.

INTERVENTIONS

The sheep were instrumented with lung lymph fistulas and received a continuous infusion with live Pseudomonas aeruginosa for 48 hrs. After 40 hrs, the atrial natriuretic peptide-receptor antagonist HS-142-1 was continuously infused in the HS-124-1 group (3 mg/kg/hr, n = 6) for 8 hrs, whereas the control group received the carrier (n = 6).

MEASUREMENTS AND MAIN RESULTS

Lung lymph flow was markedly elevated in response to sepsis after 40 hrs in both groups. Atrial natriuretic peptide-receptor blockade further increased lymph flows by 41 +/- 17% (41 hrs) up to 64 +/- 20% (44 hrs, p < .05) in the presence of normal permeability to protein. Although mean pulmonary artery pressure increased (p < .05 vs. 40 hrs), capillary pressure remained unaffected. Despite identical fluid balances in both groups, cardiovascular filling variables significantly increased in the HS-142-1 group. This was associated with increasing cardiac index and mean arterial pressure (p < .05 vs. 40 hrs). In the control group, all variables remained constant between 41 and 48 hrs.

CONCLUSION

Blockade of atrial natriuretic peptide receptors increases pulmonary transvascular fluid flux independent of changes in permeability to protein in chronic ovine sepsis. Atrial natriuretic peptide may therefore play a protective role for the alveolar-capillary barrier during sepsis.

Plasma Level of B-Type Natriuretic Peptide as a Prognostic Marker After Acute Myocardial Infarction

Background— Circulating levels of B-type natriuretic peptide (BNP), a cardiac hormone, reflect the severity of cardiac dysfunction. Because the plasma BNP level changes dramatically during the period after the onset of acute myocardial infarction (AMI), identification of a suitable sampling time is problematic. There have been several reports indicating that the plasma BNP level obtained in the acute phase of AMI can be used as a prognostic marker. We examined whether the plasma BNP level measured 3 to 4 weeks after the onset of AMI represents a reliable prognostic marker for patients with AMI.

Methods and Results— We analyzed 145 consecutive patients with AMI. Plasma BNP levels were measured during the 3 to 4 weeks after onset of AMI. Of those patients, 23 experienced fatal cardiac events during this study. The mean follow-up period was 58.6 months. Log BNP, left ventricular end-diastolic pressure, and pulmonary vascular resistance were all significantly higher in the cardiac death group, and there were more men and more patients with a history of heart failure in the cardiac death group. A Cox proportional hazards model analysis showed that log BNP was an independent predictor of cardiac death. The survival rate was significantly higher in patients with log BNP <2.26 (180 pg/mL) than in those with log BNP ≥2.26.

Conclusions— The plasma BNP level obtained 3 to 4 weeks after the onset of AMI can be used as an independent predictor of cardiac death in patients with AMI.

Omapatrilat Decreased Macrophage Oxidative Status and Atherosclerosis Progression in Atherosclerotic Apolipoprotein E-Deficient Mice

Oxidative stress is an important risk factor in the pathogenesis of atherosclerosis. Angiotensin-converting enzyme (ACE) inhibitors attenuate atherosclerosis and oxidative stress in animal models. Omapatrilat, a VasoPeptidase-inhibitor, selectively inhibits both Neutral-Endo-Peptidase (NEP) and ACE.

OBJECTIVE

In this study, we analyzed the effect of Omapatrilat administration (1, 4, or 20mg/kg/d, for 12 weeks) to atherosclerotic apolipoprotein E-deficient (E0) mice on their blood pressure (BP), serum and macrophage oxidative status, and atherosclerotic lesion area.

RESULTS

Following administration of Omapatrilat (4 mg/kg/d and 20 mg/kg/d), the mice systolic and diastolic BP significantly decreased by up to 33% and 25% respectively, compared with placebo-treated mice. However, administration of Omapatrilat at 1mg/kg/d did not affect the mice BP. The Omapatrilat-treated mice serum susceptibility to lipid peroxidation was reduced by up to 21%, and their serum paraoxonase activity was increased by up to 24%, compared with placebo-treated mice. Peritoneal macrophages from Omapatrilat-treated (20 mg/kg/d) mice exhibited a reduced oxidative stress, evidenced by a reduction in macrophage lipid peroxide content (by 45%), cholesteryl-linoleate hydroperoxide content (by 48%), and oxidized glutathione levels (by 40%). Finally, the area of the mice atherosclerotic lesion was dose-dependently reduced, by 50%, 67%, and 82%, following Omapatrilat administration at 1mg/kg/d, 4 mg/kg/d, and 20 mg/kg/d respectively, compared with placebo-treated mice.

CONCLUSION

Omapatrilat has a substantial anti-atherosclerotic effect, which can be related not only to BP reduction but also to its ability to reduce oxidative stress in atherosclerotic E0 mice.

Secretion of A-type and B-type natriuretic peptides into the bloodstream and pericardial space in children with congenital heart disease

OBJECTIVE

To determine the secretion of A-type and B-type natriuretic peptides into the bloodstream and pericardial space in children with congenital heart disease.

METHODS

Plasma and pericardial fluid samples were obtained from 77 patients undergoing total correction for congenital heart disease. All patients underwent detailed right-sided and left-sided cardiac catheterization preoperatively.

RESULTS

A-type natriuretic peptide levels in pericardial fluid were lower than those in plasma (33.0 +/- 23.1 versus 39.8 +/- 33.6 pg/mL, P <.05), and B-type natriuretic peptide levels in pericardial fluid showed marked elevations compared with those in plasma (231.9 +/- 305.6 versus 19.8 +/- 29.3 pg/mL, P <.0001). The A-type and B-type natriuretic peptide levels in plasma correlated with those in pericardial fluid (R =.522, P <.0001; R =.595, P <.0001). For A-type and B-type natriuretic peptide levels in plasma, the relation with biventricular volume had the highest correlation (R =.669, P <.0001; R =.652, P <.0001). The patients with a pulmonary-to-systemic flow ratio greater than 2 (n = 19) had high levels of natriuretic peptides not only in plasma (58.3 +/- 43.2, 40.5 +/- 49.4 pg/mL, P <.05) but also in pericardial fluid (44.4 +/- 31.5, 287.2 +/- 198.5 pg/mL, P <.05), and higher correlation between A-type and B-type natriuretic peptide plasma levels and left ventricular volume (R =.913, P <.0001; R =.787, P <.0001).

CONCLUSIONS

B-type natriuretic peptide is secreted not only into the bloodstream but also into the pericardial space in children with congenital heart disease. Natriuretic peptide levels in plasma correlated well with biventricular volume. The left ventricle was considered to be the main source of secreted natriuretic peptides in the patients with a pulmonary-to-systemic flow ratio greater than 2.

TA repeat variation, Npr1 expression, and blood pressure: impact of the Ace locus

The activity of the atrial natriuretic peptide receptor (Npr1) is altered in spontaneously hypertensive rats (SHR) in relation to its mRNA levels, suggesting abnormal transcriptional control in hypertension. A single-stranded conformational polymorphism caused by a repetitive dinucleotide segment of 10 TA in BN-Lx and of 40 TA in SHR was localized at position -943 relative to the transcription start site of the Npr1 gene, downstream of a putative cGMP-regulatory region, and was the only sequence difference noted between the two strains. Transient transfections of -1520 to -920 Npr1 promoter-SV40-luciferase fusion vector showed that the construct from BN-Lx stimulated the SV40 promoter, whereas that from SHR slightly inhibited it. In contrast to the BN-Lx construct, the activity of the SHR fragment was refractory to downregulation by atrial natriuretic peptide. Genotype-phenotype correlation studies in recombinant inbred strains (RIS) derived from BN-Lx and SHR crosses revealed significant correlations of the TA repeat with basal guanylyl cyclase activity and Npr1 mRNA levels. The correlations were heightened by a locus on chromosome 10 containing the Ace gene. The highest basal guanylyl cyclase activity and Npr1 mRNA values were found in RIS with both genes (Npr1/Ace) of BN genotypes, whereas the lowest were recorded in RIS, with the SHR genotypes at both loci. This was inversely correlated with diastolic blood pressure in these strains. In conclusion, the longer TA repeat unit in the promoter of Npr1 of SHR, in tandem with a putative cGMP responsive element, regulates the transcription of the Npr1 gene with consequences on diastolic blood pressure.

Atrial natriuretic peptide gene transfer by means of intranasal administration attenuates airway reactivity in a mouse model of allergic sensitization

Atrial natriuretic peptide (ANP) is a bronchodilator; however, the short half-life of ANP in vivo limited its therapeutic utility to treat asthma. The efficacy of intranasally administered plasmid DNA-expressing ANP (pANP; amino acid 99-126; Acc. No. XM131840) on the prevention of allergen-induced airway hyperresponsiveness (AHR) was examined in this study by using a mouse model of asthma. Ovalbumin-sensitized mice were treated with pANP versus control plasmids, and AHR was monitored after ovalbumin challenge for 5 weeks on 10-day intervals starting 4 days after gene transfer. Mice administered pANP demonstrated significantly less AHR for 20 days after treatment. The results demonstrate that pANP gene transfer protects against AHR and might be useful in the treatment of asthma.

B-type natriuretic peptide as a marker of the effects of enalapril in patients with heart failure

BACKGROUND

A-Type and B-type natriuretic peptides are cardiac hormones whose circulating levels reflect the severity of heart failure. It is not known how plasma levels of these hormones respond to changes in cardiac function that occur as a result of treatment with angiotensin-converting enzyme (ACE) inhibitors.

METHODS

Enalapril was administered at 5 mg/d for 3 months in 24 patients with chronic heart failure, and for the next 3 months at 15 mg/d in the high-dose group (n = 12) and 5 mg/d in the low-dose group (n = 12). We measured plasma levels of A-type or B-type natriuretic peptides, as well as conventional measures of cardiac function, such as the cardiothoracic ratio, left ventricular end-diastolic volume, and percent fractional shortening.

RESULTS

Mean (+/- SD) plasma levels of both hormones decreased promptly after 2 weeks of therapy (A-type natriuretic peptide: 140 +/- 107 pg/mL to 81 +/- 68 pg/mL, P = 0.01; B-type natriuretic peptide: 305 +/- 278 pg/mL to 190 +/- 178 pg/mL, P = 0.01). These reductions were sustained throughout therapy. In contrast, the cardiothoracic ratio, left ventricular end-diastolic dimension, and percent fractional shortening had not changed significantly after 3 months of treatment, although improvements were seen after 6 months of treatment. After 6 months, plasma levels of both A-type and B-type natriuretic peptides were significantly lower in the high-dose group than in the low-dose group (A-type natriuretic peptide: 48 +/- 25 pg/mL vs. 57 +/- 27 pg/mL, P = 0.01; B-type natriuretic peptide: 78 +/- 58 pg/mL vs. 139 +/- 61 pg/mL, P = 0.005), whereas no significant differences were observed in the other measures of cardiac function.

CONCLUSION

Plasma levels of A-type and B-type natriuretic peptides appear to be more sensitive markers of heart failure than conventional echocardiographic parameters and cardiothoracic ratios. Measurement of these hormones might be useful for monitoring the effects of treatment with ACE inhibitors.

Molecular cloning and functional characterization of the upstream rat atrial natriuretic peptide promoter

OBJECTIVE

The upregulation of left ventricular atrial natriuretic peptide (ANP) serves as a molecular marker of cardiac hypertrophy. The precise mechanisms underlying this gene induction are unclear, since the presently cloned 3.6 kilo base (kb) rat ANP promoter failed to substantially induce coupled reporter genes in chronically hypertrophied hearts. The aim of this study was to clone and to functionally analyse the upstream ANP promoter.

DESIGN

Upstream of the known ANP promoter, a 1.5 kb segment was cloned by the promoter walker method and found to harbour a putative CCAAT-binding site as well as multiple putative transcription factor binding sites. This newly cloned segment was ligated with a reporter gene, in vivo transfected into rat myocardium, and analysed under basal conditions or after stimulation with both acute (isovolumetric contractions in the Langendorff apparatus) and chronic wall stress (aortic banding).

RESULTS

Reporter gene constructs carrying the newly cloned segment conferred only little promoter activity. In hearts exposed to acute wall stress, the previously cloned 3.6 kb ANP promoter as well as a constitutive promoter (pGL3 promoter vector) were active but markedly suppressed after extension with the newly cloned upstream promoter (-88.1 and -85.5%; P < 0.05 respectively). Site directed mutagenesis of two AP-2 transcription factor binding sites (base pairs -3946 to -3954 or -4192 to -4200) eliminated this silencing effect. In hearts with chronic pressure overload hypertrophy as well as in normal, unstimulated hearts the activity of the 3.6 kb ANP promoter was weak and also abolished after ligation with the 1.5 kb upstream segment. Moreover, both putative AP-2 binding sites within the upstream rat ANP promoter bound specifically to nuclear proteins of unstimulated, acute and chronic pressure overloaded hearts as demonstrated by electrophoresis mobility shift assays.

CONCLUSION

Novel silencer elements were cloned, localized to two AP-2 binding sites in the upstream ANP promoter, and functionally characterized. Given that the putative upregulation of left ventricular ANP by the extensively studied 3.6 kb proximal promoter region is substantially diminished by the newly cloned segment, the functional significance of regulatory elements within the proximal promoter region should be re-evaluated. The molecular mechanism causing ANP mRNA induction in left ventricular hypertrophy remains obscure.

Comparison of transthoracic Doppler echocardiography and natriuretic peptides in predicting mean pulmonary capillary wedge pressure in patients with chronic atrial fibrillation

The purpose of this study was to assess whether transthoracic Doppler echocardiography and serum natriuretic peptide levels could predict mean pulmonary capillary wedge pressure (PCWP) in patients with chronic atrial fibrillation. We examined mitral flow velocity and pulmonary venous flow (PVF) velocity patterns in 32 patients with chronic atrial fibrillation. Plasma A-type and B-type natriuretic peptide (ANP, BNP, respectively) levels in the peripheral vein were measured. Significant correlations were observed between mean PCWP and the following: peak velocity (r = 0.51) and deceleration time (r = -0.65) of the mitral flow; peak velocity (r = 0.64) and deceleration time (r = -0.80) of the PVF; BNP (r = 0.60); and ANP (r = 0.36). Stepwise multiple linear regression analysis selected PVF deceleration time and mitral flow deceleration time as independent predictors of PCWP. A cutoff value of PVF deceleration time of < or =150 ms and a mitral flow deceleration time of < or =100 ms predicted a mean PCWP of > or =18 mm Hg, with a sensitivity of 100% and 80% and a specificity of 96% and 85%, respectively. In conclusion, PVF deceleration time and mitral flow deceleration time obtained from transthoracic Doppler echocardiography are more accurate predictors of mean PCWP than values obtained with natriuretic peptides in patients with chronic atrial fibrillation.

Increased blood pressure and loss of anp-induced natriuresis in mice lacking DARPP-32 gene

Atrial natriuretic peptide (ANP) is an important regulator of sodium metabolism and indirectly of blood pressure. Evidence has accumulated that ANP regulates sodium metabolism through a cascade of steps involving an increase in the level of cGMP, activation of cGMP-dependent protein kinase (PKG), and inhibition of renal tubular Na+, K+-ATPase activity. One of the major substrates for PKG is DARPP-32. In the present study we observed that ANP does not induce natriuresis in mice that lack DARPP-32. In contrast, there was a 4-fold increase in urinary sodium excretion following ANP administration to wild type mice. ANP as well as Zaprinast, a selective inhibitor of cGMP phosophodiesterase, inhibited renal Na+, K+-ATPase activity in wild type mice but had no such effect in mice lacking DARPP-32. Mean arterial blood pressure, measured in conscious animals, was significantly increased in DARPP-32 deficient mice as compared to wild type mice. The results confirm that DARPP-32 acts as a third messenger in the ANP signaling pathway in renal tissue and suggest an important role of DARPP-32 in the maintenance of normal blood pressure.

Regional cardiac expression and concentration of natriuretic peptides in patients with severe chronic heart failure

The purpose of this study was to examine the regional cardiac mRNA expression and concentration of brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) in relation to the circulating peptide concentrations in patients with chronic heart failure (CHF). The myocardial mRNA levels and peptide concentrations of BNP and ANP were analysed in seven different regions of the heart from patients undergoing cardiac transplantation. Autopsy samples from individuals without known cardiovascular disease were used as controls. The plasma levels of natriuretic peptides and their N-terminal propeptides, Nt-proBNP and Nt-proANP, were measured in the CHF patients and healthy volunteers. In the autopsy specimens, the atrial regions appeared to contain the highest peptide levels for BNP as well as ANP, the atrioventricular ratio being 12-262 and 72-637-fold, respectively. In the CHF patients there was a relative shift towards the ventricle for BNP, reducing the atrioventricular ratio to 6-16-fold. The circulating concentrations of BNP/Nt-proBNP in the CHF patients correlated closely to the BNP mRNA expression in most myocardial regions including the left ventricle (r = 0.72, P < 0.001). For circulating concentrations of ANP/Nt-proANP, such correlation were limited to the left atrium free wall (r = .66, P < 0.002). Thus, of the two natriuretic peptides, BNP/Nt-proBNP may be a better reflector of left ventricular overload.

Brain natriuretic peptide predicts chronic atrial fibrillation after ventricular pacing in patients with sick sinus syndrome

Chronic atrial fibrillation (AF) is one of the main complications of sick sinus syndrome (SSS). As previously reported, plasma brain natriuretic peptide (BNP), reflects hemodynamic changes in different pacing modes, as does plasma atrial natriuretic peptide (ANP), so the present study investigated whether plasma BNP or ANP can predict chronic AF after single-chamber ventricular (VVI) pacemaker implantation in patients with SSS. Plasma ANP and BNP levels were measured before and 1-3 months after implantation in 99 SSS patients. Long-term follow-up was conducted with chronic AF as an endpoint. Chronic AF occurred in 19 patients during a mean follow-up of 5.1 years. Plasma ANP and BNP were significantly higher in the patients who developed chronic AF after implantation than in those who did not, despite similar ANP and BNP levels between the 2 groups before implantation. Post-implant high BNP and a history of paroxysmal AF were independent predictors of chronic AF by a multivariate Cox proportional hazards analysis. Plasma BNP can predict the development of chronic AF after VVI pacemaker implantation in patients with SSS because increased levels may reflect latent hemodynamic abnormalities, which may contribute to the development of AF after VVI pacemaker implantation.

Suppression of the secretion of atrial and brain natriuretic peptide after total cavopulmonary connection

OBJECTIVES

Among the modifications of the Fontan operation currently being used, total cavopulmonary connection offers the greatest potential for optimizing early and long-term postoperative outcomes. Although studies have established that abrupt increases in right atrial pressure elevate the plasma atrial natriuretic peptide level after the Fontan procedure, changes in plasma natriuretic peptide levels after total cavopulmonary connection have not been clarified. Our hypothesis is that secretion of atrial natriuretic peptide may be suppressed in patients undergoing total cavopulmonary connection because the atrium continues to function at low pressure in those patients. In this study, we measured plasma levels of atrial and brain natriuretic peptide before and during the postoperative period in patients undergoing total cavopulmonary connection.

METHODS

We evaluated 60 patients: 30 patients underwent total cavopulmonary connection and 30 patients underwent definitive repair for Fallot's tetralogy. Blood samples for measurement of atrial and brain natriuretic peptide were obtained before the operation and in the postoperative period.

RESULTS

Plasma levels of atrial and brain natriuretic peptide were significantly lower during the early postoperative period in patients undergoing total cavopulmonary connection than in patients undergoing definitive repair for Fallot's tetralogy. No correlations were identified between the atrial natriuretic peptide levels and central venous pressure after total cavopulmonary connection.

CONCLUSION

These results suggest that total cavopulmonary connection attenuates the secretion of atrial and brain natriuretic peptide in the early postoperative period. The suppressed release of atrial and brain natriuretic peptide after total cavopulmonary connection may have clinical importance.

The role of atrial natriuretic peptide in alcohol withdrawal: a peripheral indicator and central modulator?

Changes in fluid and electrolyte homeostasis may accompany and are likely to modify the clinical symptoms of alcohol-withdrawal reactions. It was of obvious theoretical and practical interest therefore to investigate the changes in the secretion of hormones, which regulate the fluid and electrolyte homeostasis (atrial natriuretic peptide, aldosterone and plasma renin activity) during alcohol withdrawal in chronic alcoholic patients. In a phase of severe withdrawal, there were increased plasma renin activity and aldosterone levels observed. In a phase of partial recovery, on the other hand, the elevated plasma renin activity and aldosterone levels were back to the normal range. In 60% of the patients, delirium tremens was gradually developing during the observation period. In these patients, an elevated level of atrial natriuretic peptide was observed at the time of hospital admission, i.e. days before the actual onset of delirium tremens. It is concluded that the disturbed volume homeostasis and the consequently altered plasma atrial natriuretic peptide secretion might be associated with, and therefore used as an indicator of the onset of delirium tremens. To study the role of central nervous atrial natriuretic peptide, mice were rendered tolerant to and dependent on alcohol with an alcohol-liquid diet for 14 days. Five hours after withdrawal from alcohol, withdrawal hyperexcitability symptoms were analyzed. Intracerebroventricular (i.c.v.) injection of atrial natriuretic peptide attenuated, whereas that of an antiserum against atrial natriuretic peptide intensified the severity of handling-induced convulsions. N-methyl-D-aspartate induced behavioral seizures in a dose-dependent manner, whose effect was more intensive during the alcohol-withdrawal period than in alcohol-naive animals. I.c.v. injections of atrial natriuretic peptide dose-dependently inhibited, whereas that of antiserum against atrial natriuretic peptide potentiated the seizure-inducing effect of N-methyl-D-aspartate in alcohol-dependent mice. Although tentatively, it is concluded that peripheral secretion of atrial natriuretic peptide may be an indicator, whereas central nervous atrial natriuretic peptide a neuropeptide modulator of alcohol-withdrawal symptomatology.

Contrasting cardiac regional responses of A-type and B-type natriuretic peptide to experimental chronic heart failure

OBJECTIVE

The aim of this study was to examine the regional myocardial variation in atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) synthesis during development of congestive heart failure (CHF).

METHODS

Heart failure was induced by left atrial rapid pacing for 3 weeks in pigs. The gene expression of ANP and BNP was measured by northern blot analysis and the peptide concentration in myocardial tissue and plasma by radioimmunoassay (RIA).

RESULTS

At the end of the pacing period pulmonary capillary wedge pressure (PCWP) and right atrial pressure (RAP) increased, and cardiac output (CO) decreased compared to sham-operated controls (PCWP: 17.6 +/- 1.9 vs. 3.1 +/- 0.9 mmHg) (RAP: 10.4 +/- 1.7 vs. 2.2 +/- 0.6 mmHg) (CO: 3.5 +/- 0.4 vs. 5.3 +/- 0.3 l/min), indicating a state of moderate to severe CHF. The gene expression and tissue concentration of BNP was low in sham pigs, but was strongly increased in all cardiac regions, and especially in the left ventricle, during CHF. In contrast, ANP was mainly produced in the atria both in normal and heart failure conditions. The relative increases in mRNA levels, tissue concentrations and circulating peptide concentrations were more profound for BNP than for ANP.

CONCLUSIONS

In response to CHF induction, ANP and BNP respond differently across the cardiac regions. Strong expression of the BNP gene was only found in the heart failure state, while ANP was clearly expressed also in the normal state. These findings support the concept of BNP being superior to ANP as a biochemical marker of CHF.

Plasma renin activities, angiotensin II concentrations, atrial natriuretic peptide concentrations and cardiopulmonary function values in dogs with severe heartworm disease

Relationships among plasma renin activities (PRA), plasma angiotensin II (ATII) concentrations, atrial natriuretic peptide (ANP) concentrations and cardiopulmonary function values were examined in dogs with ascitic pulmonary heartworm disease and acute- and chronic-vena caval syndrome (CS). PRA, plasma ATII concentration and plasma ANP concentration tended to be higher or were significantly higher in dogs with ascites, acute- and chronic-CS. PRA correlated significantly with plasma ATII concentration, WBC count, ALP activity, plasma concentrations of urea nitrogen, creatinine, sodium, potassium, and chloride, right ventricular endodiastolic pressure and right atrial pressure. Plasma ATII concentration correlated significantly with WBC count, plasma concentrations of urea nitrogen, sodium, and potassium, right ventricular endodiastolic pressure and right atrial pressure. Plasma ANP concentration did not correlate with PRA or ATII concentration, but correlated significantly only with pulmonary arterial pressure.

Bronchoprotective effects of atrial natriuretic peptide against propranolol-induced bronchoconstriction after allergic reaction in guinea pigs

OBJECTIVE

To study the effects of intravenous atrial natriuretic peptide (ANP) on antigen-induced bronchoconstriction, propranolol-induced bronchoconstriction (PIB) after antigen challenge, and histamine-induced bronchoconstriction in guinea pigs.

METHODS

Allergic bronchoconstriction was evoked by inhalation of ovalbumin (OA) and PIB was caused when 10 mg/mL of propranolol was inhaled 20 min after OA challenge in passively sensitized and artificially ventilated guinea pigs. 25, 50, 100 and 200 microg/mL of histamine were inhaled for 20 s at 5-min intervals in non-sensitized guinea pigs.

RESULTS

Pretreatment with ANP in doses of 0.1 and 1.0 nmol/kg injected intravenously 15 min after antigen challenge reduced PIB in a dose-dependent manner, and 5 min before antigen challenge significantly attenuated PIB but not antigen-induced bronchoconstriction. Intravenous ANP significantly reduced bronchial responses to increasing concentrations of inhaled histamine in a dose-dependent manner.

CONCLUSION

These results suggest that ANP possesses protective effects against propranolol-induced and histamine-induced bronchoconstriction, albeit by a non-specific mechanism in guinea pig in vivo.

B-type natriuretic peptide receptor expression and activity are hormonally regulated in rat ovarian cells

Natriuretic peptides form a family of structurally related peptides known to regulate salt and water homeostasis and to cause vasodilation. Synthesis of atrial (ANP), brain (BNP), and C-type (CNP) natriuretic peptides occurs mainly in the heart and brain and has been identified recently in the female reproductive tract. The expression of ANP and CNP as well as their cognate guanylyl cyclase receptors (NPR-A and NPR-B, respectively) have been detected in the rat ovary. We have shown previously that the expression of the natriuretic peptides and their receptors in the rat ovary appears to be modulated by the estrous cycle. In the present study we have evaluated the expression of the natriuretic peptide system (peptide and receptor) in ovarian cells (granulosa and thecal-interstitial cells) obtained from immature female rats treated with either diethylstilbestrol (DES), an estrogen analog, or equine CG (eCG), a gonadotropin that possesses both LH and FSH activity. Using a whole cell RRA, we found that CNP binding was increased by 2-fold in granulosa cells taken from animals treated with either DES or eCG. Semiquantitative RT-PCR revealed that granulosa cells from DES- or eCG-treated animals have increased levels of NPR-B messenger RNA (mRNA) transcripts, which was in good agreement with the increased binding. The activity of the receptors was assessed by ligand-dependent stimulation of cGMP release. CNP, but not ANP, stimulated the release of cGMP from granulosa cells obtained from DES-treated, but not from eCG-treated, animals. The relative levels of CNP mRNA in granulosa cells were unaltered by either DES or eCG treatment. In contrast, CNP mRNA levels were increased more than 2-fold, but only in theca-interstitial from the eCG-treated animals. Our results indicate that CNP and NPR-B are expressed in the ovary, and their expression is responsive to hormonal treatments. Furthermore, expression of these components of the natriuretic peptide system appears to be compartmentalized, with CNP being derived from the extrafollicular compartment and acting, through NPR-B, on the granulosa cells.