Alpha-atrial Natriuretic Peptide Research Articles

A Clinical and Physiological Prospective Observational Study on the Management of Pediatric Shock in the Post-Fluid Expansion as Supportive Therapy Trial Era.

ObjectivesFluid bolus resuscitation in African children is harmful. Little research has evaluated physiologic effects of maintenance-only fluid strategy.DesignWe describe the efficacy of fluid-conservative resuscitation of septic shock using case-fatality, hemodynamic, and myocardial function endpoints.SettingPediatric wards of Mbale Regional Referral Hospital, Uganda, and Kilifi County Hospital, Kenya, conducted between October 2013 and July 2015. Data were analysed from August 2016 to July 2019.PatientsChildren (≥ 60 d to ≤ 12 yr) with severe febrile illness and clinical signs of impaired perfusion.InterventionsIV maintenance fluid (4 mL/kg/hr) unless children had World Health Organization (WHO) defined shock (≥ 3 signs) where they received two fluid boluses (20 mL/kg) and transfusion if shock persisted. Clinical, electrocardiographic, echocardiographic, and laboratory data were collected at presentation, during resuscitation and on day 28. Outcome measures were 48-hour mortality, normalization of hemodynamics, and cardiac biomarkers.Measurement and main ResultsThirty children (70% males) were recruited, six had WHO shock, all of whom died (6/6) versus three of 24 deaths in the non-WHO shock. Median fluid volume received by survivors and nonsurvivors were similar (13 [interquartile range (IQR), 9–32] vs 30 mL/kg [28–61 mL/kg], z = 1.62, p = 0.23). By 24 hours, we observed increases in median (IQR) stroke volume index (39 mL/m2 [32–42 mL/m2] to 47 mL/m2 [41–49 mL/m2]) and a measure of systolic function: fractional shortening from 30 (27–33) to 34 (31–38) from baseline including children managed with no-bolus. Children with WHO shock had a higher mean level of cardiac troponin (t = 3.58; 95% CI, 1.24–1.43; p = 0.02) and alpha-atrial natriuretic peptide (t = 16.5; 95% CI, 2.80–67.5; p < 0.01) at admission compared with non-WHO shock. Elevated troponin (> 0.1 μg/mL) and hyperlactatemia (> 4 mmol/L) were putative makers predicting outcome.ConclusionsMaintenance-only fluid therapy normalized clinical and myocardial perturbations in shock without compromising cardiac or hemodynamic function whereas fluid-bolus management of WHO shock resulted in high fatality. Troponin and lactate biomarkers of cardiac dysfunction could be promising outcome predictors in pediatric septic shock in resource-limited settings.

Isolated atrial amyloid: a potential contributor to morbidity and mortality following cardiac surgery.

Diffuse cardiac amyloidosis is a significant diagnosis with a poor prognosis. Isolated atrial amyloidosis (IAA) is the most common form of cardiac amyloidosis caused by accumulation of alpha-atrial natriuretic peptide. IAA has been associated with dysrhythmia, but otherwise remains a poorly characterized condition. The impact of incidental IAA on postoperative outcome following cardiac surgery has not previously been reported. The purpose of this study was to examine the impact of isolated atrial amyloid on patient outcomes following cardiac surgery. A retrospective analysis was performed of all patients having excision of the left atrial appendage during cardiac surgery at our centre over a 5-year period. Patients with histological evidence of IAA were compared to patients without this diagnosis. IAA was diagnosed by immunohistochemistry for atrial natriuretic peptide. A total of 167 patients underwent left atrial appendage excision and of these 26 (15.6%) were found to have IAA. Preoperative characteristics were similar between the 2 groups. A significantly greater proportion of patients with IAA experienced dysrhythmia requiring implantation of a permanent pacemaker (23.1% vs 7.8%, P = 0.03). There was also a significantly elevated incidence of perioperative death in the IAA group (11.5% vs 1.4%, P = 0.03) and inferior 1-year survival (84.6% vs 96.5%, P = 0.02). The presence of IAA may be associated with inferior outcomes following cardiac surgery, with increased morbidity in the early postoperative period and inferior long-term survival. Knowledge of the diagnosis preoperatively may facilitate management of patients.

Mating Behavior Increases Workload of the Heart in Thoroughbred Stallions

To evaluate the influence of mating behavior on cardiac function, changes in heart rate (HR), electrocardiogram (ECG), hematocrit (Hct) and serum concentration of alpha-atrial natriuretic peptide (alpha-ANP) were evaluated in 10 clinically sound Thoroughbred stallions before and after mating behavior. The stallions were submitted twice to experimental pseudomating in the same month in 2009 and 2010. Measurements and blood samples were collected at a stable before mating (baseline) and at a covering yard before and after mating. ECG was recorded by a Holter-ECG system. Arrhythmias were detected in 5 stallions before or after mating behavior. Minimum HR (HRmin), maximum HR (HRmax) and HR recorded when the stallions entered into yard (HRent) and ejaculated (HRejc) were 34.2 ± 3.7, 168.9 ± 14.2, 141.8 ± 35.3 and 142.6 ± 27.3 beats/min, respectively. Time from entrance into the yard to ejaculation (mating time; MT) ranged from 30 to 2,103 sec and was highly correlated with HRent (r=-0.82) and the time required for attaining HRmax after entrance into the yard (dT HRmax) (r=0.87). Hct and serum alpha-ANP concentration significantly increased after ejaculation (60.0 ± 3.2%, P<0.0001, and 1.54 ± 0.61 ng/ml, P=0.0353) compared with the baselines values (46.9 ± 4.4%, 1.40 ± 0.60 ng/ml). HRent and Hct were significantly higher in the stallions with an MT of less than 5 min (n=5) compared with those (n=5) with an MT of more than 5 min (P=0.0324 and P=0.0082). Mating behavior increases the workload of the heart in Thoroughbred stallions.

Blunted Autonomic Response to Volume Expansion in Formerly Preeclamptic Women with Low Plasma Volume

We hypothesize that low plasma volume in normotensive formerly preeclamptic women reflects reduced venous storage capacity. To test this hypothesis, we compared circulatory and autonomic responses to acute volume loading between women with low and those with normal plasma volume. In 24 normotensive formerly preeclamptic women at least 6 months postpartum, we administered 500 mL of iso-oncotic fluid by constant intravenous infusion in 30 minutes, while recording changes in heart rate, blood pressure, cardiac output, and measuring active plasma renin and alpha-atrial natriuretic peptide concentrations. We estimated arterial sympathetic control, cardiac autonomic regulatory balance, and baroreflex sensitivity using spectral analysis. Intergroup and intragroup changes were analyzed nonparametrically. 17 women (71%) had low plasma volume and 7 (29%) had normal plasma volume. Plasma volume expansion induced comparable changes in blood pressure, heart rate, baroreflex sensitivity, and active plasma renin concentration in low plasma volume and normal plasma volume. Cardiac output and alpha-atrial natriuretic peptide increased in low plasma volume but not in normal plasma volume. Volume expansion reduced sympathetic activity ( from 2.41 to 1.76 mm Hg(2), P = .03) in normal plasma volume but not in low plasma volume ( from 2.72 to 2.48 mm Hg(2), P > .05). The sympathoinhibitory response to volume expansion is diminished in low plasma volume, which suggests that cardiovascular reflex function is impaired. We speculate that this defect contributes to circulatory maladaptation to pregnancy, sympathetic dominance, and the development of gestational hypertensive disease.

Formerly Preeclamptic Women With a Subnormal Plasma Volume Are Unable to Maintain a Rise in Stroke Volume During Moderate Exercise

In formerly preeclamptic women with a low plasma volume, the recurrence rate of preeclampsia is higher than in women with a normal prepregnant plasma volume. In a recent study, we demonstrated that the low plasma volume subgroup also had a subnormal venous capacitance. In the present study, we determined the impact of subnormal plasma volume on the hemodynamic response to moderate exercise. We performed this study in the follicular phase of the menstrual cycle, in 31 formerly preeclamptic women with a subnormal plasma volume (low-PV) and eight parous controls. The exercise consisted of 60 minutes of cycling in the supine position at 35% of the individualized maximum capacity. Before, during, and after cycling, we measured the percentage change in heart rate, stroke volume, and cardiac output. Before and after exercise, we measured the effective renal plasma flow (ERPF, para-amino-hippurate [PAH] clearance), glomerular filtration rate (GFR, inulin clearance), circulating levels of alpha-atrial natriuretic peptide (alpha-ANP), and active plasma renin concentration (APRC). The response to exercise of formerly preeclamptic women with a subnormal plasma volume differed from that in controls by a lack of rise in stroke volume, a smaller rise in cardiac output and alpha-ANP, and a greater fall in GFR. The responses in heart rate, ERPF, and APRC did not differ between the two groups. The response to moderate exercise of formerly preeclamptic women with a subnormal plasma volume differs from that in healthy parous controls with a normal plasma volume and suggests a lower capacity to raise venous return in conditions of a higher demand for systemic flow. The lower capacity to raise venous return in these conditions is associated with more cardiovascular drift. The physiologic consequence is a lower aerobic endurance performance during moderate exercise.

A Subnormal Plasma Volume in Formerly Preeclamptic Women is Associated with a Low Venous Capacitance

Pregnancy induces a smaller rise in plasma volume in formerly preeclamptic women with a pre-existent subnormal plasma volume than in their counterparts with a normal plasma volume. These women also have a three times higher recurrence rate of pregnancy-induced hypertensive disorders. In this study we tested the hypothesis that a subnormal plasma volume in these women is related to a lower capacitance of their venous compartment. In 31 nonpregnant formerly preeclamptic women with a subnormal plasma volume and eight parous controls, we infused intravenously 500 mL of a modified gelatin solution over 30 minutes. Before and after infusion we measured the circulating levels of alpha-atrial natriuretic peptide (alpha-ANP) and active plasma renin concentration (APRC). During volume loading, we recorded the change in heart rate, stroke volume, and cardiac output using pulse contour analysis. We measured the ratio of percent change in blood volume and percent change in cardiac output during volume loading as a marker for venous capacitance. During volume loading, patients differed from controls by a larger rise in alpha-ANP, pulse rate, and cardiac output, and by a lower estimated venous capacitance. The concomitant response of stroke volume and APRC did not differ appreciably between groups. Formerly preeclamptic women with a subnormal plasma volume differ from controls with a normal plasma volume by a reduced venous capacitance. These results support our hypothesis that, in these women, a subnormal plasma volume indicates the presence of a subnormal venous capacitance.

Synthetic human alpha-atrial natriuretic peptide infusion in management after open heart operations.

Cardiopulmonary bypass (CPB) induces water retention in the third space, and the mechanism is partially associated with the activation of the renin-angiotensin-aldosterone system (RAAS). Atrial natriuretic peptide (ANP) has a gradual but strong diuretic effect and suppresses the RAAS activation. We examined the efficacy of synthetic human alpha-ANP (hANP) infusion in the management of the postoperative water balance control. Thirty patients (male:female = 18:12, 65.2 +/- 9.5 years) undergoing elective open heart operations in 2001 were allocated into one of two groups. Group H (n = 14) received 0.025 microg/kg/minute of synthetic hANP (HANP; Suntory Inc., Zeria Pharmaceutical, Tokyo, Japan) from the termination of CPB; the dose was gradually reduced to 0 until the 72nd postoperative hour. Group C (n = 16) served as control subjects. Twenty-four hours after operation, the central venous pressure, mean pulmonary arterial pressure, and pulmonary capillary wedge pressure were significantly lower in group H than in group C, and the cardiac index was significantly higher in group H. Total volume of plasma solution infused during the initial 24 postoperative hours was significantly smaller in group H. The total dosages of furosemide and potassium-chloride added during the first 72 postoperative hours were significantly smaller in group H. On the first postoperative day, plasma levels of renin activity and aldosterone were significantly lower in group H. These results suggest that postoperative hANP infusion, which provides a sufficient diuretic effect and suppresses CPB induced RAAS activation, may simplify management after open heart operations.

Preeclampsia and maladaptation to pregnancy: A role for atrial natriuretic peptide?

The majority of women with a history of preeclampsia have either an underlying thrombophilic disorder or a vascular disorder. In this study, we tested the hypothesis that only the latter condition predisposes for abnormal hemodynamic adaptation to pregnancy. Thirty-seven formerly preeclamptic subjects were subdivided into a hypertensive (HYPERT, N = 10), a normotensive thrombophilic (THROMB, N = 13) and a normotensive nonthrombophilic subgroup (NONTHROMB, N = 14). In these women and in 10 normal parous controls, the following variables were measured at least five-months postpartum at day 5 (+/-2) of the menstrual cycle and again at five- and seven-weeks amenorrhea in the next pregnancy: mean arterial pressure, heart rate, cardiac output, central cardiovascular dimensions, plasma volume, glomerular filtration rate, effective renal plasma flow, 17-beta estradiol, progesterone, the hormones of the renin-angiotensin-aldosterone (RAAS) axis, catecholamines and alpha-atrial natriuretic peptide. The early pregnancy rise in cardiac output, renal variables, RAAS activity, and plasma volume was comparable in all groups. However, the HYPERT and NONTHROMB subgroups differed from controls by a lower plasma volume in the prepregnant state. In addition, only the women in these two subgroups responded to pregnancy by a rise in circulating alpha-atrial natriuretic peptide. In addition, at seven weeks, in the subjects belonging to the HYPERT and NONTHROMB subgroups, plasma volume was the lowest and correlated inversely with the concomitant circulating level of alpha-atrial natriuretic peptide. The hemodynamic adaptation to pregnancy in the HYPERT and NONTHROMB subgroups differs from that in THROMB and controls by an early pregnancy rise in alpha-atrial natriuretic peptide. As a consequence, the early pregnancy plasma volume expansion in the NONTHROMB and HYPERT subgroups is less than in normal parous controls.

Plasma levels of N-terminal peptide of pro-atrial natriuretic peptides in myoskeletal injuries

To determine whether concentrations of the N-terminal peptide of pro-atrial natriuretic peptide (proANP) and of alpha atrial natriuretic peptide 1–28 ( aANP) releases are affected by myoskeletal injuries, samples from 24 patients with muscle injuries were therefore collected within 48 h of injury. The mean age of patients was 65; range: 17–90 years. These were compared with 18 non-injured subjects with a mean age of 40; range: 17–80 years. A specific enzyme immunoassay (EIA) method suitable for the determination of proANP and aANP was used. aANP required plasma extraction and no extraction was needed for proANP determination. ProANP level was significantly higher in patients on admission and this level was maintained 24 h after admission ( p<0.05) compared to controls. However, aANP 1–28 level remained statistically unchanged in the patients samples. The level of proANP was over 10 times greater than the levels obtained with aANP. N-terminal peptide of proANP may be a supplementary tool in the study of early phase of myoskeletal injuries in human.

Alpha-atrial natriuretic peptide, cyclic guanosine monophosphate, and endothelin in plasma as markers of myocardial depression in human septic shock.

To assess the value of alpha-atrial natriuretic peptide (alpha-ANP), second messenger cyclic guanosine monophosphate (cGMP,) and endothelin as markers of myocardial depression in septic shock. Prospective observational study. Medical intensive care unit (ICU) of a university hospital. Fourteen consecutive patients with septic shock and arterial and pulmonary artery catheters in place. Hemodynamic variables and plasma levels of alpha-ANP, cGMP, and endothelin were measured every 6 hrs for 3 days after admission. Eight patients died from shock in the ICU. The nadir left ventricular stroke work index (LVSWI) was below 35 g/m2 in all patients, and the median peak circulating alpha-ANP (n < 68 pg/mL) was 276 pg/mL (range, 79-1056), the median peak cGMP (n < 2.1 ng/mL) was 8.1 ng/mL (range, 3.2-29.7), and the median peak endothelin (n < 5.3 pg/mL) was 15.5 pg/mL (range, 8.5-33.9), supranormal in all patients. Outcome groups differed in the course of cardiac index and LVSWI, which were lower in nonsurvivors despite similar filling pressures and more intensive inotropic treatment (p < .01). The course of alpha-ANP, cGMP, and endothelin plasma levels also differed between groups, with higher levels in nonsurvivors (p < .05). As for pooled data, the mean daily or nadir LVSWI inversely related to mean daily or peak alpha-ANP, cGMP, and endothelin levels, respectively (p < .05). The area under the receiver operating characteristic curve for myocardial depression (LVSWI < 35 g/m2) was for alpha-ANP and endothelin 0.77, and for cGMP 0.85 (p < .01). The optimum cutoff values for alpha-ANP, cGMP, and endothelin were 172 pg/mL, 4.5 ng/mL, and 10.0 pg/mL, respectively. The sensitivity for myocardial depression of alpha-ANP, cGMP, and endothelin was 68%, 77%, and 72%, and the specificity was 82%, 93%, and 69%, respectively. Circulating alpha-ANP, endothelin, and, particularly, cGMP may be markers of the myocardial depression of human septic shock, which is associated with mortality.

Low dose carvedilol inhibits progression of heart failure in rats with dilated cardiomyopathy.

The cardioprotective properties of carvedilol (a vasodilating beta-adrenoceptor blocking agent) were studied in a rat model of dilated cardiomyopathy induced by autoimmune myocarditis. Twenty-eight days after immunization, surviving Lewis rats (32/43=74%) were divided into three groups to be given 2 mg kg(-1) day(-1) (Group-C2, n=10) or 20 mg kg(-1) day(-1) (Group-C20, n=10) of carvedilol, or vehicle (0.5% methylcellulose, Group-V, n=12). After oral administration for 2 months, body weight, heart weight (HW), heart rate (HR), rat alpha-atrial natriuretic peptide (r-ANP) in blood, central venous pressure (CVP), mean blood pressure (mean BP), peak left ventricular pressure (LVP), left ventricular end-diastolic pressure (LVEDP), +/-dP dt(-1) and area of myocardial fibrosis were measured. Values were compared with those for normal Lewis rats (Group-N, n=10). Two out of 12 (17%) rats in Group-V died from day 28 to day 42 after immunization. No rat died in Groups-C2, -C20 and -N. Although the CVP, mean BP, LVP and +/-dP dt(-1) did not differ among the three groups, the HW, HR and r-ANP in Group-C2 (1.14+/-0.03, 339+/-16 and 135+/-31) and Group-C20 (1.23+/-0.04, 305+/-8 and 156+/-24) were significantly lower than those in Group-V (1.36+/-0.04 g, 389+/-9 beats min(-1) and 375+/-31 pg ml(-1), respectively). The LVEDP in Group-C2 was significantly lower than that in Group-V (7.4+/-1.4 and 12.2+/-1.2 mmHg, respectively, P<0. 05). The area of myocardial fibrosis in Group-C2 was smaller than that in Group-V (12+/-1 and 31+/-2%, P<0.01). These results indicate that a low dose of carvedilol has beneficial effects on dilated cardiomyopathy.

AlphaANP, AVP, and pituitary-thyroid axis in patients with congestive heart failure and acute respiratory failure.

The pituitary-thyroid axis and neurohumoral activation indexes were simultaneously investigated in 16 in-patients hospitalized for cardiac heart failure (CHF), New York Heart Association (NYHA), class II-IV, and Killip clinical scale, class II-III, to evaluate their relationship with CHF morbidity and the relative prognostic value. At entry the patients were divided into two subgroups (A and B), according to the severity of CHF. Patients were further classified into two subgroups, according to the subsequent clinical course (C, poor outcome and D, improved clinical course). Blood samples were obtained every day for the radioimmunoassay measurement of plasma alpha-atrial natriuretic peptide (alphaANP), arginine vasopressin (AVP), and thyroid hormones, and the results were compared with those of 12 control subjects. At admission, alphaANP and 3,3',5'-triiodothyronine (rT3) values were higher, while 3,3',5-triiodothyronine (T3) to rT3 (T3/rT3) ratio was lower in subgroups A and B than in controls (p<0.001), respectively, and in C than in D (p<0.001), respectively, according to the prognosis. Conversely, no differences in other thyroid indexes, nor a significant correlation between alphaANP and either rT3 or T3/rT3 ratio were present in any of the subgroups. AVP plasma levels in subgroup A were not statistically different from those of controls, whereas they were significantly decreased in subgroups B and C (p<0.05) and D (p<0.001). In conclusion, these results indicate that in CHF the pituitary-thyroid axis is not altered, that alphaANP and T3/rT3 ratio are non-invasive and reliable predictors of severity and prognosis, while AVP might be affected by the different pathological processes leading to CHF or by the concomitant use of drugs.

Natriuretic peptides and the acclimation of aglomerular toadfish to hypo-osmotic media.

Since the aglomerular toadfish (Opsanus tau) experiences a natriuresis following transfer to 10% seawater, we examined the role of natriuretic peptides in the acclimation of toadfish to hypo-osmotic media. Gel filtration chromatography of acid extracts of toadfish heart and kidney identified a broad peak of atrial natriuretic peptide-like immunoreactivity in both tissues, with maximal immunoreactivity in fractions coeluting with human alpha-atrial natriuretic peptide. Using a homologous bioassay to measure changes in aortic ring tension, both vasorelaxing and, surprisingly, vasoconstricting bioactivities were identified in gel fractions of heart extract. No significant vasorelaxing activity was identified in kidney extract or fractions. Instead, a potent vasoconstricting activity was observed, with maximal activity in gel fractions with an estimated MW greater than 1000 Da. Levels of atrial natriuretic peptide immunoreactivity in plasma from the caudal vein were very low in seawater toadfish and were unchanged 12 h after transfer of toadfish to 10% seawater. We conclude, that natriuretic peptides are present in the heart and kidney of toadfish. However, atrial natriuretic peptide-like peptides of cardiac origin circulating to the kidney via the caudal vein do not appear responsible for the natriuresis that ensues upon the transfer of toadfish to 10% seawater. In the absence of glomeruli, this tubular natriuresis may be regulated by natriuretic peptides present in the kidney.

Calcitonin gene-related peptide, neuropeptide Y and atrial natriuretic peptide distribution in guinea pig heart from paraffin wax-embedded and formalin-cryoprotected tissues.

In this study, the distributions of calcitonin gene-related peptide, neuropeptide Y, and alpha-atrial natriuretic peptide 1-28 immunoreactivity, were investigated within different regions of the guinea pig heart by utilising two different methods of tissue fixation for the immunocytochemistry. The results were compared with data obtained through radioimmunoassays. We observed similar concentrations and distributions of alpha-atrial natriuretic peptide in the right atrium, with results of radioimmunoassay and immunocytochemistry, but there were no myocytes containing alpha-atrial natriuretic peptide in the left atrium or ventricles with immunocytochemistry as opposed to radioimmunoassay. The immunoreaction obtained for neuropeptide Y was more intense in the right ventricle than left. Calcitonin gene-related peptide nerve fibres were about twice as abundant in the left atrium than in the right.

Measurement of circulating immunoreactive alpha-atrial natriuretic peptide in human plasma: validation and clinical application.

Recent evidence suggests that plasma alpha-atrial natriuretic peptide (alpha-ANP) may serve as a useful biochemical marker of severe heart failure, as circulating levels become ighly elevated. In the present study, a specific radioimmunoassay (RIA) protocol was adapted and optimised for rapid quantitative measurement of circulating alpha-ANP levels in plasma taken from clinically normal subjects and heart transplant recipients with no evidence of heart failure or heart transplant rejection. The plasma concentration of immunoreactive alpha-ANP in heart transplant recipients (115 +/- 10 pg/ml, n = 14) was significantly higher (p < 0.01) than in normal subjects (14 +/- 5 pg/ml, n = 20). Comparison of circulating plasma immunoreactive alpha-ANP levels obtained by the adapted assay to levels obtained by a standard RIA protocol revealed a significant correlation (r = 0.998, y = 1.004 x -2.94, n = 40). The adapted assay is simple, precise, and with a shorter incubation time that would enable results to be available within one working day. These results show that circulating biological active a-ANP levels are elevated in healthy heart transplant recipients with no evidence of heart failure; thus extending previous reports concerning the elevation in circulating alpha-ANP levels from patients with a wide range of heart disorders. The adapted RIA protocol would facilitate rapid detection and quantification of alpha-ANP in experimental research and routine clinical investigations.

Extraction of human alpha atrial natriuretic peptide and its physiological validation

A very sensitive and specific radioimmunoassay for human alpha atrial natriuretic peptide (hANP) and a novel extraction method for hANP, have been developed. Antiserum to hANP showed no cross-reactivity with related analogues (e.g., brain natriuretic peptide). The radioimmunoassay can detect 1.2 fmol ANP/assay tube. Using a commercially available tracer, the antiserum binds 0.7 fmol of radioligand at a final dilution of 1:96 000. Production of ANP tracer, using 125I, Iodogen and reversed-phase HPLC separation, produces two products. The first has identical properties to the commercial reagent resulting in an identical antibody titre. The second, however, is more reactive with the antiserum which can be employed at a final dilution of 1:192K. These products represent oxidised and reduced peptides, respectively, inferring that the commercial tracer is oxidised. The recovery of synthetic hANP from plasma over the range of 0–1000 ng/l through Sep-Pak C 18 cartridges, using an extraction method of acetic acid–acetonitrile (4:96) was 89%. Inter- and intra-assay coefficients of variation were 9.5% and 8.2%, respectively. The radioimmunoassay was validated in man by measuring plasma ANP (ng/l) following change of posture and exercise in normal man. Plasma ANP rose from 13.2 (1.0; S.D.) to 20.1 (1.6) from supine to sitting position. Plasma ANP increased to 20.1 (1.6) at rest (sitting) to 34 (2.7) ng/l at peak of exercise, but decreased from 31.2 (2.5) to 21.4 (0.1) ng/l at 3 and 6 min after exercise, respectively. These results confirm that the assay is capable of differentiating changes of concentrations within the physiological range.

Inhibition of goby posterior intestinal NaCl absorption by natriuretic peptides and by cardiac extracts.

Natriuretic peptides abolish active Na+ and Cl- absorption across the posterior intestine of the euryhaline goby Gillichthys mirabilis. Inhibition by eel and human natriuretic peptides is dose-dependent with the following sequence of potencies based on experimentally determined ID50 values for inhibition of short-circuit current: eel ventricular natriuretic peptide (78 nmol.l-1), eel atrial natriuretic peptide (156 nmol.l-1), human brain natriuretic peptide (326 nmol.l-1), human alpha atrial natriuretic peptide (1.05 mumol.l-1), and eel C-type natriuretic peptide (75 mumol.l-1). Natriuretic peptides also significantly increase transcellular conductance. The observed sequence of natriuretic peptide potencies is suggestive of cellular mediation by GC-A-type NP-R1 receptors in this tissue; as expected for guanylyl-cyclase-coupled NP-R1 receptors, cyclic GMP mimics the action of natriuretic peptides on the goby intestine. Crude aqueous extracts of goby atrium and ventricle inhibited short circuit current and increased tissue conductance in a dose-dependent manner. Ventricular extract was more potent than atrial extract on both a per organ and per milligram basis.

Atrial natriuretic peptide, sodium retention, and proteinuria in nephrotic syndrome

Oedema formation in the nephrotic syndrome is primarily due to tubular sodium retention. The pathogenetic role of alpha atrial natriuretic peptide (ANP), a hormonal promoter of natriuresis is unknown. In 31 patients (aged 35+/-11 years) with nephrotic syndrome and histopathological evidence of primary glomerulonephritis, we investigated plasma ANP concentration and its influence on renal haemodynamics, natriuresis, and proteinuria (total protein, albumin, IgG excretion). Patients with a compensated treated form of nephrotic syndrome due to primary glomerulonephritis were included in the study. Serum creatinine levels were <=1.4 mg/dl. Diuretic medication was discontinued at least 24 h before the investigation was started. Patients were randomly assigned to ANP infusion (0.005 microg/kg*min; group II, n=15) or received placebo (group III, n=16). Ten healthy subjects (group I) served as normal controls. In normal subjects (group I), ANP caused an increase in natriuresis from 14.5+/-4.2 mmol/h to 26.4+/-11.1 mmol/h (P<0.01). In patients with nephrotic syndrome (group II), baseline sodium excretion of 10.5+/-6.0 mmol/h was increased to 19.6+/-14.8 mmol/h with ANP infusion (P<0.01). No changes were seen in the placebo group III. The absolute increase in ANP induced natriuresis was not significantly different between group I and II. However, plasma ANP levels were significantly higher in patients with nephrotic syndrome (166+/-87 pg/ml vs. 74+/-21 pg/ml, P<0.05) and also reached higher levels after ANP infusion (P<0.01). Therefore, natriuresis was significantly reduced when circulating ANP levels were taken into account (P<0.05). ANP administration resulted in an increase of total protein excretion in patients with the nephrotic syndrome (group II, from 219+/-277 mg/h to 264+/-268 mg/h). Albumin elimination rose from 128+/-151 mg/h to 167+/-170 mg/h (P<0.05) and IgG excretion from 4.91+/-6.67 mg/h to 9.27+/-10.78 mg/h (P<0.05). Healthy subjects also showed a small but significant increase in albuminuria (48+/-38%, P<0.05). Low-dose ANP infusion did not, however, induce any significant alteration in GFR, ERPF and blood pressure. ANP plasma concentrations in the steady state are elevated in patients with the nephrotic syndrome. The natriuretic effect of ANP is reduced when referring to circulating ANP plasma levels. Elevated ANP levels enhance urinary protein excretion in the nephrotic syndrome. This is not due to modulation of GFR or FF, but is most probably attributable to increased glomerular permeability.

The effect of long-term treatment with spironolactone on variceal pressure in patients with portal hypertension without ascites

The effect of spironolactone on esophageal variceal pressure (VP) in patients without ascites was investigated. VP was assessed using a noninvasive endoscopic gauge. Spironolactone was administered during a 6-week period at a dosage of 100 mg/d. This treatment decreased VP from 16.8 +/- 1.9 (SD) to 14.1 +/- 2.7 mm Hg (P < .001) in a group of 12 patients and from 18.6 +/- 2.1 to 13.7 +/- 4.1 mm Hg (P < .01) in another group of 8 patients who still had high VP despite chronic intake of propranolol. In both groups, placebo administration to 12 and 8 comparable patients did not significantly alter VP. Spironolactone induced a significant reduction of plasma volume (42.1 +/- 5.5 to 36.1 +/- 6.6 mL/kg body weight, P < .01) and of the concentration of alpha-atrial natriuretic peptide (alpha-ANP) (39.8 +/- 22 to 27.7 +/- 20 pg/mL, P < .01); in addition, a pronounced increase in plasma renin activity (PRA) (1.1 +/- 0.9 to 7.5 +/- 3.4 ng/mL/h, P < .001) was induced by the treatment. No significant changes in systemic hemodynamics were observed during the studies. Severe side effects were not observed except for a high incidence (55%) of painful gynecomasty in the male patients. In conclusion, chronic spironolactone administration effectively lowers VP, even in patients under chronic propranolol therapy. The combination of propranolol and spironolactone deserves further study as a prophylactic therapy of variceal hemorrhage, but development of gynecomasty might be a problem. Finally, we confirmed the reproducibility of VP measurements with the noninvasive gauge in chronic conditions. (Hepatology 1996 May;23(5):1047-52)

Stimulation of atrial natriuretic peptide release by neurokinins in neonatal rat ventricular cardiomyocytes.

The effect of substance P (SP) on atrial natriuretic peptide (ANP) release was studied in neonatal rat ventricular cardiomyocytes. Incubation of cells with SP led to a marked increase in ANP secretion, a response accompanied by increases in alpha-type protein kinase C (PKC) in the membranous cell fraction and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) formation and a small increase in adenosine 3',5'-cyclic monophosphate (cAMP) production. A role for PKC in SP-induced 6-keto-PGF1 alpha formation and ANP release was apparent insofar as the responses were suppressed by PKC inhibitors and in PKC-downregulated cells. Furthermore, SP-induced 6-keto-PGF1 alpha production was strongly correlated with SP-induced ANP secretion (r = 0.91, P < 0.0001, n = 27), suggesting a role for prostaglandins in SP-mediated ANP release. Supporting this, indomethacin abolished SP-induced ANP release, whereas PGE2, PGF2 alpha, and prostacyclin (PGI2) promoted ANP secretion in this system. Both the profile of SP-induced cAMP production and results obtained with prostaglandin antagonists suggest that a prostanoid FP receptor is at the basis of this response. Finally, both neurokinins A and B induced similar ANP responses, whereas cultured cells were found to contain mRNA transcripts coding for both neurokinin NK1 and NK3 receptor subtypes. Overall, these results suggest that SP induces ANP secretion in neonatal ventricular cardiomyocytes through a PKC- and prostaglandin-dependent signaling pathway.