Plasma Atrial Natriuretic Peptide Levels Research Articles

Oleanolic acid‐induced regulation of atrial natriuretic peptide secretion in perfused beating atrial model

The heart is an endocrine organ involved in the regulation of blood pressure and body fluid homeostasis through the secretion of atrial natriuretic peptide (ANP). Oleanolic acid (OA) is a well known triterpenoid compound that exist widely in food and medicinal herbs. The purpose of present study was to examine the effect of OA in the regulation of ANP secretion. Experments were performed in beating rat atria. OA (30 mg/kg/day) was administrated orally in Sprague‐Dawley rats : Atrial dynamics, pulse pressure, and ANP secretion were measured. OA administration increased ANP levels in plasma and atria. To identify the effects of OA on the ANP secretion by activation of ¥â‐adrenergic and muscarinic receptor, isoproterenol and acetylcholine were administration in the atria from OA‐ and sham‐treatie rats. Oral intake of OA accenturated the acetylcholine‐induced increase of ANP secretion. However, OA attenuated the isoproterenol‐induced decrease of ANP secretion. These findings demonstrate that OA attenuates the decrease of ANP secretion induced by activation of ¥â‐adrenergic receptor and accentuates the increase of ANP secretion induced by muscarinic receptor. These results suggest that oral intake of OA induces an activation of the ANP system in rats.

The dual endothelin converting enzyme/neutral endopeptidase inhibitor SLV-306 (daglutril), inhibits systemic conversion of big endothelin-1 in humans

AimsInhibition of neutral endopeptidases (NEP) results in a beneficial increase in plasma concentrations of natriuretic peptides such as ANP. However NEP inhibitors were ineffective anti-hypertensives, probably because NEP also degrades vasoconstrictor peptides, including endothelin-1 (ET-1). Dual NEP and endothelin converting enzyme (ECE) inhibition may be more useful. The aim of the study was to determine whether SLV-306 (daglutril), a combined ECE/NEP inhibitor, reduced the systemic conversion of big ET-1 to the mature peptide. Secondly, to determine whether plasma ANP levels were increased. Main methodsFollowing oral administration of three increasing doses of SLV-306 (to reach an average target concentration of 75, 300, 1200ngml−1 of the active metabolite KC-12615), in a randomised, double blinded regime, big ET-1 was infused into thirteen healthy male volunteers. Big ET-1 was administered at a rate of 8 and 12pmolkg−1min−1 (20min each). Plasma samples were collected pre, during and post big ET-1 infusion. ET-1, C-terminal fragment (CTF), big ET-1, and atrial natriuretic peptide (ANP) were measured. Key findingsAt the two highest concentrations tested, SLV-306 dose dependently attenuated the rise in blood pressure after big ET-1 infusion. There was a significant increase in circulating big ET-1 levels, compared with placebo, indicating that SLV-306 was inhibiting an increasing proportion of endogenous ECE activity. Plasma ANP concentrations also significantly increased, consistent with systemic NEP inhibition. SignificanceSLV-306 leads to inhibition of both NEP and ECE in humans. Simultaneous augmentation of ANP and inhibition of ET-1 production is of potential therapeutic benefit in cardiovascular disease.

Comparative study of therapeutic effects of short- and long-acting loop diuretics in outpatients with chronic heart failure (COLD-CHF)

Loop diuretics have two different classes with different duration of activity: short-acting such as furosemide (duration of activity, 6h) and long-acting such as azosemide (duration of activity, 10-12h). We conducted a multicenter, randomized, controlled trial in order to compare the therapeutic effects of azosemide, a long-acting loop diuretic, and furosemide, a short-acting one, on neurohumoral factors and cardiac function in outpatients with chronic heart failure (CHF). We enrolled 98 patients with CHF who were receiving furosemide and an angiotensin-converting enzyme inhibitor, and they were randomly divided into furosemide (n=49) and azosemide (n=49) groups. The furosemide group continued furosemide at the same dosage, and the azosemide group switched from furosemide to azosemide. At baseline and after 3 months, we measured body weight, and levels of brain natriuretic peptide (BNP), atrial natriuretic peptide (ANP), norepinephrine, active renin, creatinine, blood urea nitrogen, sodium, potassium, and hematocrit. Chest X-ray and echocardiography were also performed. Body weight and plasma levels of BNP and ANP significantly decreased after 3 months in the azosemide group compared to the furosemide group. There were no significant differences in changes of levels of creatinine, blood urea nitrogen, sodium, potassium, hematocrit, norepinephrine, and active renin after 3 months between the furosemide and azosemide groups. Echocardiography and chest X-ray did not demonstrate significant differences between the two groups. Long-acting azosemide is suggested to be useful for the improvement of neurohumoral factors compared with short-acting furosemide in patients with CHF.

Pioglitazone does not modify ANP levels of type 2 diabetic patients

Background: The atrial natriuretic peptide (ANP) regulates fluid volume redistribution between heart and the pulmonary vessels. In diabetic patients the physiological action of ANP appears to be seriously altered. Methods: 12 subjects (gender 6M/6F, age 47 ± 2 years, BMI 29.1 ± 0.1 kg/m2), with type 2 diabetes and under stable conditions, were studied after one month of pioglitazione treatment (30 mg/die) by means of isotonic blood volume expansion. Results: After one month of pioglitazone treatment the meta- bolic profile of the subjects improved (decrease dia- stolic blood pressure: p = 0.05, total cholesterol: p = 0.01, triglycerides: p = 0.03 and blood glucose: p = 0.01) as the expansion of their plasma volume was found associated with the decrease of hematocrit (p < 0.05). The statistical comparison before versus after pioglitazone showed a significant decrease in the ba- sal aldosterone levels post-treatment (p < 0.04). Nonetheless ANP plasma levels were similar before and after therapy. Conclusions: The inappropriately high concentrations of ANP induced by hyperglyce-mia and the abnormal responses to a physiological sti- mulus like an isotonic blood volume expansion are not reverted by one month of pioglitazone. This is in contrast with the brisk improvement of the metabolic profile seen for the same period of treatment. ANP secretion is modified by fluid load in diabetic patients. This anomaly is not reverted by pioglitazone.

Sleep deprivation induces excess diuresis and natriuresis in healthy children

Urine production is reduced at night, allowing undisturbed sleep. This study was undertaken to show the effect of sleep deprivation (SD) on urine production in healthy children. Special focus was on gender and children at an age where enuresis is still prominent. Twenty healthy children (10 girls) underwent two 24-h studies, randomly assigned to either sleep or SD on the first study night. Diet and fluid intake were standardized. Blood samples were drawn every 4 h during daytime and every 2 h at night. Urine was fractionally collected. Blood pressure and heart rate were noninvasively monitored. Blood was analyzed for plasma antidiuretic hormone (AVP), atrial natriuretic peptide (ANP), angiotensin II, aldosterone, and renin. Urine was analyzed for aquaporin-2 and PGE(2). Successful SD was achieved in all participants with a minimum of 4 h 50 min, and full-night SD was obtained in 50% of the participants. During SD, both boys and girls produced markedly larger amounts of urine than during normal sleep (477 ± 145 vs. 291 ± 86 ml, P < 0.01). SD increased urinary excretion of sodium (0.17 ± 0.05 vs. 0.10 ± 0.03 mmol·kg(-1)·h(-1)) whereas solute-free water reabsorption remained unchanged. SD induced a significant fall in nighttime plasma AVP (P < 0.01), renin (P < 0.05), angiotensin II (P < 0.001), and aldosterone (P < 0.05) whereas plasma ANP levels remained uninfluenced (P = 0.807). Nighttime blood pressure and heart rate were significantly higher during SD (mean arterial pressure: 78.5 ± 8.0 vs. 74.7 ± 8.7 mmHg, P < 0.001). SD leads to natriuresis and excess diuresis in healthy children. The underlying mechanism could be a reduced nighttime dip in blood pressure and a decrease in renin-angiotensin-aldosterone system levels during sleep deprivation.

NT-proBNP, but not ANP and C-reactive protein, is predictive of paroxysmal atrial fibrillation in patients undergoing pulmonary vein isolation

The purpose of this study is to evaluate the relationship between plasma high-sensitivity C-reactive protein (hs-CRP), atrial natriuretic peptides (ANP), N-terminal-pro-brain natriuretic peptide (NT-proBNP) levels, and the risk and recurrence of atrial fibrillation (AF) after pulmonary vein isolation (PVI) in patients with paroxysmal atrial fibrillation (PAF). Plasma ANP, NT-proBNP, and hs-CRP levels were measured before and 3 months after PVI in 33 patients with PAF and 30 control participants. (1) NT-proBNP levels at baseline were significantly elevated in subjects with PAF compared with control subjects (296.8 ± 272.1 vs. 80.8 ± 69.1 pg/ml), but ANP and hs-CRP levels were normal; NT-proBNP levels normalized 3 months after PVI, but ANP and hs-CRP levels did not change significantly; NT-proBNP levels at baseline in the recurrent group were markedly higher than those in the nonrecurrent AF group (572.7 ± 234.2 vs. 176.8 ± 188.7 pg/ml). (2) Cox stepwise multivariate analysis demonstrated that only elevated NT-proBNP level at baseline was an independent predictor of AF recurrence (p < 0.001) after PVI among 13 variables, such as echocardiographic parameters, plasma ANP, NT-proBNP, and hs-CRP levels. A cutoff value of NT-proBNP ≥ 423.2 pg/ml was a significant risk factor for AF recurrence (p = 0.002). Elevated NT-proBNP level at baseline, but not ANP and hs-CRP, is a sensitive biomarker for early predicting AF recurrence in patients with PAF.

Involvement of the atrial natriuretic peptide in the reduction of arterial pressure induced by swimming but not by running training in hypertensive rats

The aim of this study was to compare, under resting conditions, the influence of chronic training in swimming or running on mean arterial pressure (MAP) and the involvement of the natriuretic peptide system in this response. Two-month-old male spontaneously hypertensive rats (SHR) were divided into three groups—sedentary (SD), swimming (SW) and running (RN)—and were trained for eight weeks under regimens of similar intensities. Atria tissue and plasma atrial natriuretic peptide (ANP) concentrations were measured by radioimmunoassay. ANP mRNA levels in the right and left atria as well as the natriuretic peptide receptors (NPR), NPR-A and NPR-C, mRNA levels in the kidney were determined by real-time PCR. Autoradiography was used to quantify NPR-A and NPR-C in mesenteric adipose tissue. Both training modalities, swimming and running, reduced the mean arterial pressure (MAP) of SHR. Swimming, but not running, training increased plasma levels of ANP compared to the sedentary group (P<0.05). Expression of ANP mRNA in the left atrium was reduced in the RN compared to the SD group (P<0.05). Expression of NPR-A and NPR-C in the kidneys of the SW group decreased significantly (P<0.05) compared to the SD group. Although swimming increased 125I-ANP binding to mesenteric adipose tissue, displacement by c-ANF was reduced, indicating a reduction of NPR-C. These results suggest that the MAP reduction induced by exercise in SHR differs in its mechanisms between the training modalities, as evidenced by the finding that increased levels of ANP were only observed after the swimming regimen.

Estradiol potentiates hypothalamic vasopressin and oxytocin neuron activation and hormonal secretion induced by hypovolemic shock

Estrogen receptors are located in important brain areas that integrate cardiovascular and hydroelectrolytic responses, including the subfornical organ (SFO) and supraoptic (SON) and paraventricular (PVN) nuclei. The aim of this study was to evaluate the influence of estradiol on cardiovascular and neuroendocrine changes induced by hemorrhagic shock in ovariectomized rats. Female Wistar rats (220-280 g) were ovariectomized and treated for 7 days with vehicle or estradiol cypionate (EC, 10 or 40 μg/kg, sc). On the 8th day, animals were subjected to hemorrhage (1.5 ml/100 g for 1 min). Hemorrhage induced acute hypotension and bradycardia in the ovariectomized-oil group, but EC treatment inhibited these responses. We observed increases in plasma angiotensin II concentrations and decreases in plasma atrial natriuretic peptide levels after hemorrhage; EC treatment produced no effects on these responses. There were also increases in plasma vasopressin (AVP), oxytocin (OT), and prolactin levels after the induction of hemorrhage in all groups, and these responses were potentiated by EC administration. SFO neurons and parvocellular and magnocellular AVP and OT neurons in the PVN and SON were activated by hemorrhagic shock. EC treatment enhanced the activation of SFO neurons and AVP and OT magnocellular neurons in the PVN and SON and AVP neurons in the medial parvocellular region of the PVN. These results suggest that estradiol modulates the cardiovascular responses induced by hemorrhage, and this effect is likely mediated by an enhancement of AVP and OT neuron activity in the SON and PVN.

The effect of β1-blocker bisoprolol on atrial natriuretic peptide plasma levels in hypertensive patients

The aim of this study was to evaluate the effects of the high selective β1-blocker bisoprolol on atrial natriuretic peptide (ANP) plasma levels in patients with a moderate essential hypertension. The study was divided into two parts: a long-term and a short-term one. In part 1, the long-term effects of the drug, given orally at a daily dose of 10 mg, on plasma ANP concentrations were studied in correlation with the blood pressure and the echocardiographic dimensions of the left heart cavities in the lying position. Plasma ANP levels were raised by 20% despite the drop in blood pressure and the very small, but statistically significant, decrease in left atrial and ventricular diameters. In part 2, the acute effects of a single oral dose of 20 mg bisoprolol in relation to postural changes were studied. Plasma ANP levels in the sitting position were lower than in when lying down, but in both positions they were slightly higher after betablockers. The above findings, taken together with the literature data, favor the theory that the antihypertensive action of beta adrenergic blockers is partially due to the increased secretion of ANP.

Process Matters

The natriuretic peptide system (NPS) provides critical compensatory actions in heart failure, including vasodilation; promoting of natriuresis; and opposing adverse neurohormonal activation, including the renin-angiotensin-aldosterone axis. The NPS also is an autocrine/paracrine neurohormonal system that enhances lusitropy, opposes cardiac hypertrophy, and retards the development of cardiac interstitial fibrosis (Figure 1).1 Tsutomota and colleagues2 were among the first to advance the concept that advanced heart failure was associated with an “attenuation of the compensatory actions” of the NPS. Using plasma cGMP levels as a surrogate biomarker for the target tissue actions of atrial natriuretic peptide (ANP) or brain natriuretic peptide (BNP), they demonstrated that in advanced heart failure (New York Heart Association class III/IV) compared to mild heart failure (class I/II), there was a reduction of the slope of the relationship between plasma ANP levels and cGMP levels; in fact, despite a nearly 4-fold higher average ANP level in patients with advanced heart failure compared to mild heart failure, plasma cGMP levels were similar. Based on these data, Tsutomota and colleagues suggested that advanced heart failure is characterized by an “attenuation of the compensatory actions of the endogenous NPS.” Figure 1. The endogenous natriuretic peptide system (NPS) exerts numerous compensatory actions. The cardiac effects are mediated by local autocrine/paracrine actions of the NPS. GFR indicates glomerular filtration rate; RAAS, renin-angiotensin-aldosterone. Article see p 114 The hypotheses offered to explain the dysregulation of the NPS in heart failure focused on the NP receptor. The receptor mediating the target tissue actions of ANP and BNP is the guanylate-cyclase type A (GC-A) receptor. The binding of ANP or BNP to GC-A initiates a conformational change in the receptor that allows the intracellular guanylate-cyclase domain of the receptor to effectively generate cGMP, the primary second messenger mediating downstream signaling cascades in target tissues (vascular …

Acute Experimental Hyperthyroidism Does Not Affect Basal and Volume-Induced Atrial Natriuretic Peptide Secretion in Healthy Subjects

Background. Excess circulating thyroid hormones are associated with increased cardiac atrial natriuretic peptide (ANP) secretion but the exact mechanisms involved have not been fully elucidated in vivo. Methods. To examine whether thyroid hormone regulation of ANP secretion is the result of a direct action on the myocardium and/or of an indirect action through alterations in the peripheral circulation, plasma ANP levels (baseline and volume expansion-induced) were evaluated in 14 healthy men, before and after triiodothyronine (T3) administration. Results. T3 administration was followed by a significant increase in serum T3 levels and a significant decrease in serum TSH levels, without significantly affecting ANP levels. Systemic vascular resistance, plasma rennin activity (PRA), and aldosterone (ALDO) levels, as well as indices of left atrial function, were not significantly altered, despite a significant increase in cardiac output. Plasma volume expansion, induced by a 1500 ml normal saline (NSal) infusion, both before and after T3 administration, was followed by a significant decrease in PRA and ALDO and a significant increase in plasma ANP levels, without significantly affecting the mean blood pressure (BP) and heart rate (HR) in each study period. The NSal-induced response, measured as the integrated area under the curve corrected for baseline values (-AUC), was not different after T3 administration for ANP, ALDO, PRA, HR, and mean BP. Conclusion. In vivo thyroid hormone-induced myocardial ANP secretion is the result of an indirect action mainly through hemodynamic changes that increase atrial stretch.

Preliminary experimental research on glucocorticoid for treatment of nitrogen dioxide induced acute pulmonary edema in rats

To investigate the therapeutic effect of glucocorticoids on the acute pulmonary edema in rats induced by nitrogen dioxide (NO₂). Thirty SD female rats were randomly equally divided into 5 groups: normal control group, NO₂ exposed group, high-, middle- and low-dose of glucocorticoids treated group (6 rats per group). 6 rats in the normal control group were exposed to room air for 30 min, and the other rats to NO₂. 18 rats in the glucocorticoids group were treated with different doses of dexamethasone (6.0, 3.0, 1.0 mg/kg), while the rats in the NO₂ poisoning group were treated with normal saline (2.5 mg/kg). The lung wet/dry (W/D) weight ratio was calculated, and plasma atrial natriuretic peptide (ANP) levels, superoxide dismutase (SOD) activity from whole blood, plasma interleukin 6 (IL-6), interleukin 10 (IL-10), tumor necrosis factor-α (TNF-α) and Interferon-γ (IFN-γ) were detected by enzyme-linked immunosorbent assay (ELISA). The lung W/D ratios were increased significantly in glucocorticoids treated group and NO₂-exposed group compared with normal control group (P < 0.05), while they were significantly reduced in glucocorticoids treated group as compared with NO₂-exposed group (P < 0.05). SOD activity in whole blood in glucocorticoids treated group and NO₂-exposed group was significantly lower than that of normal control group (P < 0.05), while it was no significant difference between that of glucocorticoids treated group and NO₂-exposed group (P > 0.05). Plasma ANP was significantly increased in NO₂-exposed group compared with normal control group (P < 0.05), while it was significantly decreased in glucocorticoids treated group compared with NO₂-exposed group (P > 0.05). Plasma TNF-α of high-, middle- and low-dose of glucocorticoids treated group [(27.04 ± 8.19), (40.10 ± 9.09), (39.76 ± 9.60) pg/ml] was decreased significantly as compared with NO₂-exposed group (68.55 ± 27.84 pg/ml) (P < 0.05). Plasma IL-6 in high- and middle-dose of glucocorticoids treated group [(15.97 ± 6.18), (19.69 ± 5.52) pg/ml] was significantly decreased as compared to NO₂-exposed group [(29.29 ± 9.31) pg/ml] (P < 0.05). Plasma IL-10 in high-, middle- and low-dose of glucocorticoids treated group [(23.24 ± 5.14), (27.78 ± 8.17), (33.29 ± 10.42) pg/ml] was significantly reduced compared with NO₂-exposed group [(44.38 ± 9.19) pg/ml] (P < 0.05). Plasma IFN-γ in high- and middle-dose of glucocorticoids treated group [(7.21 ± 4.55), (19.23 ± 4.35) pg/ml] was reduced compared with NO₂-exposed group [(30.83 ± 6.82) pg/ml] (P < 0.05). High-, middle-, low-dose glucocorticoids all can improve the permeability of alveolar wall and capillary, and have nonspecific anti-inflammatory effects. The therapeutic effects on pulmonary edema are significant. High and middle dose of glucocorticoids treated group are more useful for decreased inflammatory factors.

Prediction of Long‐Term Survival in Chronic Heart Failure by Multiple Biomarker Assessment: A 15‐Year Prospective Follow‐Up Study

In chronic heart failure (CHF), several plasma biomarkers identify subjects at risk of death over the midterm. However, their long-term predictive value in the context of other candidate predictors has never been assessed. This information may prove valuable in the management of a chronic disease with a long natural history, as CHF is today. We aimed to assess the very-long-term prognostic power of a set of biomarkers to identify CHF patients at highest risk for all-cause mortality. A group of 106 consecutive outpatients with CHF (85 male and 21 female, median age 56 y) was followed for 15 years. Echocardiographic tracings and blood samples were collected at study entry to evaluate cardiac function, plasma atrial natriuretic peptide (ANP), aldosterone, and erythropoietin, and plasma renin activity. The relationships between biomarkers, clinical and echocardiographic variables, and mortality were assessed. After 15 years, 86 of the 106 patients (81%) had died. Multivariate analysis showed that ANP was the best independent predictor of survival over several clinical, echocardiographic, and humoral variables (hazard ratio: 5.62, 95% confidence interval: 3.37-9.39, P < 0.001 for plasma levels < median value of 71 pg/mL). Plasma renin activity and erythropoietin provided prognostic information in univariate analysis, but lost their predictive power when adjusted for covariates. The present study represents the longest available follow-up of patients with CHF evaluating the prognostic power of multiple biomarkers. It shows that a simple assessment of plasma ANP levels is the strongest long-term predictor of death in all stages of heart failure.

W15.1 Pregnancy induced hypertension and subsequent health and mortality of women: a record linkage study

The decreased volume of maternal extracellular fluid in preeclamptics may result in a different rate of atrial natriuretic peptide secretion and thus affect its plasma levels. Our objectives were to determine whether there was a difference in plasma levels of atrial natriuretic peptide in the various hypertensive disorders of pregnancy. Forty-nine pregnant women in the third trimester of pregnancy were evaluated: 21 with preeclampsia, 17 with chronic hypertension during pregnancy and 11 normotensives. The atrial natriuretic peptide concentration was 13.9 ± 5.9 pg/ml, 17.8 ± 13.5 pg/ml and 16.7 ± 7.4 pg/ml in the preeclamptics, chronic hypertensives and normotensives, respectively. The differences between the three groups were not statistically significant. Atrial natriuretic peptide plasma levels remained stable in the various hypertensive disorders of pregnancy.

W15.4 Preeclampsia is probably an independent risk factor for cardiovascular disease

The decreased volume of maternal extracellular fluid in preeclamptics may result in a different rate of atrial natriuretic peptide secretion and thus affect its plasma levels. Our objectives were to determine whether there was a difference in plasma levels of atrial natriuretic peptide in the various hypertensive disorders of pregnancy. Forty-nine pregnant women in the third trimester of pregnancy were evaluated: 21 with preeclampsia, 17 with chronic hypertension during pregnancy and 11 normotensives. The atrial natriuretic peptide concentration was 13.9 ± 5.9 pg/ml, 17.8 ± 13.5 pg/ml and 16.7 ± 7.4 pg/ml in the preeclamptics, chronic hypertensives and normotensives, respectively. The differences between the three groups were not statistically significant. Atrial natriuretic peptide plasma levels remained stable in the various hypertensive disorders of pregnancy.

W15.3 Hypertension in pregnancy is associated with elevated C-reactive protein levels later in life

The decreased volume of maternal extracellular fluid in preeclamptics may result in a different rate of atrial natriuretic peptide secretion and thus affect its plasma levels. Our objectives were to determine whether there was a difference in plasma levels of atrial natriuretic peptide in the various hypertensive disorders of pregnancy. Forty-nine pregnant women in the third trimester of pregnancy were evaluated: 21 with preeclampsia, 17 with chronic hypertension during pregnancy and 11 normotensives. The atrial natriuretic peptide concentration was 13.9 ± 5.9 pg/ml, 17.8 ± 13.5 pg/ml and 16.7 ± 7.4 pg/ml in the preeclamptics, chronic hypertensives and normotensives, respectively. The differences between the three groups were not statistically significant. Atrial natriuretic peptide plasma levels remained stable in the various hypertensive disorders of pregnancy.

Urotensin II receptor antagonist attenuates monocrotaline-induced cardiac hypertrophy in rats

Urotensin II (UII) is a vasoactive peptide with potent cardiovascular effects through a G protein-coupled receptor. Hypoxia stimulates the secretion of UII and atrial natriuretic peptide (ANP). However, the effect of UII on hypoxia-induced cardiac hypertrophy is still controversial. The present study was conducted to determine whether human UII (hUII)-mediated ANP secretion influences hypoxia-induced cardiac hypertrophy using in vitro and in vivo models. Hypoxia caused an increase in ANP secretion and a decrease in atrial contractility in isolated perfused beating rat atria. hUII (0.01 and 0.1 nM) attenuated hypoxia-induced ANP secretion without changing the atrial contractility, and the hUII effect was mediated by the UII receptor signaling involving phospholipase C, inositol 1,3,4 trisphosphate receptor, and protein kinase C. Rats treated with monocrotaline (MCT, 60 mg/kg) showed right ventricular hypertrophy with increases in pulmonary arterial pressure and its diameter and plasma levels of UII and ANP that were attenuated by the pretreatment with an UII receptor antagonist, urantide. An acute administration of hUII (5 μM injection plus 2.5 μM infusion for 15 min) decreased the plasma ANP level in MCT-treated rats but increased the plasma ANP level in MCT plus urantide-treated and sham-operated rats. These results suggest that hUII may deteriorate MCT-induced cardiac hypertrophy mainly through a vasoconstriction of the pulmonary artery and partly through the suppression of ANP secretion.

β 1-Adrenergic receptor activation decreases ANP release via cAMP-Ca 2+ signaling in perfused beating rabbit atria

Aims Although a β-adrenoceptor (β-AR) blockade-induced increase in plasma atrial natriuretic peptide (ANP) levels is implicated in the therapeutic significance of β-AR antagonists, the role of β-AR in the regulation of ANP release is not clearly defined. The purpose of the present study was to define the role of β-AR subtypes and the mechanisms responsible for regulation of atrial ANP release. Main methods Experiments were performed in isolated perfused beating rabbit atria, including measurement of atrial contractile response, cAMP efflux, and atrial myocyte ANP release. Key findings β-AR activation with (–)-isoproterenol decreased ANP release concomitantly with increases in cAMP efflux concentration, atrial dynamics, stroke volume and pulse pressure in a concentration-dependent manner. The ANP response was inversely related to the change in cAMP efflux concentrations. The isoproterenol-induced decrease in ANP release was inhibited by β 1-AR blockade with CGP 20712A but not by β 2-AR blockade with ICI 118551. The isoproterenol-induced decrease in ANP release was attenuated by the L-type Ca 2+ channel antagonist nifedipine and the cAMP-dependent protein kinase inhibitor KT5720. Significance These findings suggest that β 1-AR activation decreases ANP release via cAMP- and Ca 2+-dependent mechanisms.

Involvement of the atrial natriuretic peptide transcription factor GATA4 in alcohol dependence, relapse risk and treatment response to acamprosate

In alcoholism, both relapse to alcohol drinking and treatment response are suggested to be genetically modulated. This study set out to determine whether the top 15 single nucleotide polymorphisms (SNPs) of a recent genome-wide association (GWA) and follow-up study of alcohol dependence are associated with relapse behavior and pharmacological treatment response in 374 alcohol-dependent subjects who underwent a randomized, double-blind, placebo-controlled trial with acamprosate, naltrexone or placebo. The single nucleotide polymorphism, rs13273672, an intronic SNP in the gene for GATA-binding protein 4 (GATA4), was associated with relapse within the 90-day medical treatment period (P<0.01). Subsequent pharmacogenetic analyses showed that this association was mainly based on patients treated with acamprosate (P<0.01). In line with the observation that natriuretic peptide promoters are modulated by GATA4, a significant gene dose effect on the variance of atrial natriuretic peptide (ANP) plasma concentration in the different GATA4 genotypes (P<0.01) was found. Hence, genetic variations in GATA4 might influence relapse and treatment response to acamprosate in alcohol-dependent patients via modulation of ANP plasma levels. These results could help to identify those alcohol-dependent patients who may be at an increased risk of relapse and who may better respond to treatment with acamprosate.

Homologous desensitization of guanylyl cyclase A, the receptor for atrial natriuretic peptide, is associated with a complex phosphorylation pattern

Atrial natriuretic peptide (ANP), via its guanylyl cyclase A (GC-A) receptor and intracellular guanosine 3′,5′-cyclic monophosphate production, is critically involved in the regulation of blood pressure. In patients with chronic heart failure, the plasma levels of ANP are increased, but the cardiovascular actions are severely blunted, indicating a receptor or postreceptor defect. Studies on metabolically labelled GC-A-overexpressing cells have indicated that GC-A is extensively phosphorylated, and that ANP-induced homologous desensitization of GC-A correlates with receptor dephosphorylation, a mechanism which might contribute to a loss of function in vivo. In this study, tandem MS analysis of the GC-A receptor, expressed in the human embryonic kidney cell line HEK293, revealed unambiguously that the intracellular domain of the receptor is phosphorylated at multiple residues: Ser487, Ser497, Thr500, Ser502, Ser506, Ser510 and Thr513. MS quantification based on multiple reaction monitoring demonstrated that ANP-provoked desensitization was accompanied by a complex pattern of receptor phosphorylation and dephosphorylation. The population of completely phosphorylated GC-A was diminished. However, intriguingly, the phosphorylation of GC-A at Ser487 was selectively enhanced after exposure to ANP. The functional relevance of this observation was analysed by site-directed mutagenesis. The substitution of Ser487 by glutamate (which mimics phosphorylation) blunted the activation of the GC-A receptor by ANP, but prevented further desensitization. Our data corroborate previous studies suggesting that the responsiveness of GC-A to ANP is regulated by phosphorylation. However, in addition to the dephosphorylation of the previously postulated sites (Ser497, Thr500, Ser502, Ser506, Ser510), homologous desensitization seems to involve the phosphorylation of GC-A at Ser487, a newly identified site of phosphorylation. The identification and further characterization of the specific mechanisms involved in the downregulation of GC-A responsiveness to ANP may have important pathophysiological implications.Structured digital abstract•MINT-7713870, MINT-7713887: PMCA (uniprotkb:P20020) and GC-A (uniprotkb:P18910) colocalize (MI:0403) by fluorescence microscopy (MI:0416)