A highly sensitive radioimmunoassay of atrial natriuretic peptide (ANP) in human plasma and urine

Presence of immunoreactive salusin-alpha in human serum and urine

Salusins, identified from a full-length enriched human cDNA library by bioinformatics analyses, show mitogenic, neuromodulatory and hemodynamic activities in rats. They are expressed in a wide variety of human tissues, but their precise structures and levels in human body fluids remain unknown. We developed a radioimmunoassay suitable for the detection of immunoreactive human salusin-alpha and characterized the molecular forms and concentrations of salusin-alpha in human serum and urine. The assay allowed for measurement of immunoreactive salusin-alpha concentrations as low as 1 fmol/tube after extraction of serum with an octyl-silica column, and the concentration required for 50% inhibition of binding was 40 fmol/tube. Cross-reactivities with salusin-beta and other bioactive peptides were negligible. Salusin-alpha-like immunoreactivity in normal human serum and urine ranged from 11.0 to 40.4 pmol/l (mean+/-S.D., 23.3+/-8.1 pmol/l, n=31) and from 18.6 to 367.3 pmol/l (mean+/-S.D., 156.8+/-95.8 pmol/l), respectively. Reverse-phase high performance liquid chromatography coupled with radioimmunoassay detection revealed a major immunoreactive component that coeluted with authentic salusin-alpha. These data indicate the presence of salusin-alpha in human serum and urine, thereby verifying the initially predicted processing sites for salusin-alpha in humans.

Urotensin II is an autocrine/paracrine growth factor for the porcine renal epithelial cell line, LLCPK1

Urotensin-II (UII), a cyclic dodecapeptide with potent cardiovascular effects, has recently been shown to be abundantly expressed in the human kidney and excreted in human urine. To investigate whether UII acts as an autocrine/paracrine growth factor for renal epithelial cells, we have studied the effects of human UII (hUII) on DNA synthesis, cytosolic free Ca(2+) concentration ([Ca(2+)](i)), ERK activation, and protooncogene (c-myc) expression in a porcine renal epithelial cell line (LLCPK1). hUII stimulated [(3)H]thymidine uptake into quiescent cells in a dose-dependent manner (10(-9) to 10(-7) M); this effect was inhibited by a protein kinase C inhibitor (GF109203X), a MAPK kinase inhibitor (PD98059), and a calcium channel blocker (nicardipine). Neither phosphatidyl inositol-3 kinase inhibitors (LY294002, wortmannin) nor p38 kinase inhibitor (SB203580) affected the hUII-induced DNA syntheses. hUII rapidly (within 5 min) and dose-dependently (10(-9) to 10(-7) M) increased [Ca(2+)](i) in fura-2-loaded cells. hUII also caused a rapid and transient activation of ERK1/2 and induction of c-myc. LLCPK1 cells expressed UII mRNA and its receptor GPR14 mRNA, as determined by RT-PCR, and released UII-like immunoreactivity into media. Neutralization of endogenous UII by anti-hUII antibody, but not nonimmune serum, significantly suppressed DNA synthesis. These data suggest that hUII is an autocrine/paracrine growth factor for renal epithelial cells via activation of both protein kinase C and ERK1/2 pathways as well as Ca(2+) influx via voltage-dependent Ca(2+) channels.

Atrial natriuretic peptide improves pulmonary gas exchange by reducing extravascular lung water in canine model with oleic acid-induced pulmonary edema

OBJECTIVE

The purpose of this study was to examine and compare the effects of atrial natriuretic peptide and furosemide on pulmonary gas exchange, hemodynamics, extravascular lung water, and renal function in a dog model of oleic acid-induced pulmonary edema.

DESIGN

Prospective, comparable, experimental study.

SETTING

Laboratory at a university hospital.

SUBJECTS

Eighteen male beagle dogs were studied under mechanical ventilation with pentobarbital anesthesia.

INTERVENTIONS

Oleic acid (0.08 mL/kg) was injected and allowed for 1 hr to achieve pulmonary edema with hypoxemia at Fio2 of 0.3. After lung injury, dogs were divided into three groups; control group (n = 6) receiving saline (2.5 mL/hr for 5 hrs), atrial natriuretic peptide group (n = 6) receiving atrial natriuretic peptide (1 microg x kg(-1) x min(-1) for 5 hrs), and furosemide group (n = 6) receiving furosemide (1 mg x kg(-1) x hr(-1) for 5 hrs).

MEASUREMENTS AND MAIN RESULTS

Hemodynamics, arterial blood gases, extravascular lung water, and renal function were measured hourly for 7 hrs after injury. Oleic acid increased extravascular lung water and induced hypoxemia. In the atrial natriuretic peptide group, extravascular lung water was significantly (p <.05) lower and Pao2 was significantly (p <.05) higher than in the control and furosemide groups, respectively. Pulmonary hypertension induced by oleic acid was attenuated by atrial natriuretic peptide infusion but not by saline or furosemide. Increased natriuresis/diuresis did not significantly differ between the atrial natriuretic peptide and the furosemide group, whereas creatinine clearance in the atrial natriuretic peptide group was significantly higher than that in the furosemide group.

CONCLUSIONS

These findings suggest that atrial natriuretic peptide improves pulmonary gas exchange by reducing extravascular lung water and pulmonary arterial pressure, possibly independently from natriuresis/diuresis in oleic acid-induced pulmonary edema.

Co-expression of urotensin II and its receptor (GPR14) in human cardiovascular and renal tissues

BACKGROUND

Urotensin-II (UII), a cyclic dodecapeptide originally isolated from fish urophysis that has potent cardiovascular effects, has recently been identified as an endogenous ligand for the orphan G protein-coupled receptor, GPR14. The physiological roles of endogenous UII and its receptor in humans remain unknown.

OBJECTIVE

To investigate the presence of human (h) UII-like immunoreactivity (hUII-LI) in human biological fluids, and the expression of hUII and GPR14 genes in human tissues.

METHODS

We have established a specific radioimmunoassay for hUII and the real-time quantitative reverse transcriptase polymerase chain reaction method using LightCycler for the quantification of hUII and GPR14 mRNAs.

RESULTS

Gel filtration and reverse-phase high performance liquid chromatography of human urine extracts revealed a single major peak of hUII-LI co-eluting with known hUII. The concentrations of hUII-LI in urine from normal individuals were 7.4 +/- 0.9 microg/g creatinine, whereas its plasma concentration was undetectable (< 50 pg/ml). Urinary hUII concentrations from patients with essential hypertension and those with renal tubular abnormality, but not with glomerular diseases, were significantly greater than those from normal individuals. The resulting fractional excretion of hUII, exceeding the glomerular filtration rate, suggests a renal origin of urinary UII-LI. hUII mRNAs were abundantly expressed in the kidney and the right atrium, but far less so in the vasculature, whereas GPR14 mRNAs were equally and abundantly expressed in both cardiovascular and renal tissues.

CONCLUSIONS

These data suggest that urinary hUII is derived mainly from a renal source, and that hUII functions as an autocrine/paracrine vasoactive factor not only in the cardiovascular system, but also in the kidney, with an as yet unspecified function.

Plasma human atrial natriuretic peptide, endothelin-1, aldosterone and plasma-renin activity in pregnancy-induced hypertension

OBJECTIVE

To determine the relationship between endothelin-1 (ET-1), human atrial natriuretic peptide (hANP), plasma-renin activity (PRA) and 24-h urinary excretion of aldosterone (U-Ald) in pregnancy-induced hypertension (PIH).

DESIGN AND METHODS

Plasma hANP (pg/ml), ET-1 (pg/ml), PRA (ng/ml per h) and U-Ald (microg/24 h) were measured and 24 h ambulatory mean arterial pressure (MAP) was monitored in 178 normotensive subjects (NT) and 79 gravidas with PIH at the 8th, 18th, 23rd, 28th, 32nd and 36th weeks.

RESULTS

The PIH group had higher MAP than the NT group from the 23rd week (91.64 +/- 8.76 versus 83.48 +/- 4.36 mmHg, P< 0.01) until the end of the pregnancy. ET-1 levels (pg/ml) in both groups were identical at the beginning of pregnancy and different in the 23rd week [(NT versus PIH) (35.11 +/- 17.42 and 40.2 +/- 19.51, respectively, P < 0.05)] and the 36th week (37.36 +/- 18.07 and 42.7 +/- 16.43, P< 0.05). hANP levels (pg/ml) in the NT group decreased insignificantly from the 8th till the 32nd week, then increased to 101.94 +/- 17.4 in the 36th (P< 0.001 versus any other week). In the PIH group, hANP increased from 104.8 +/- 26.8 pg/ml at the 8th week to 161.3 +/- 28.6 pg/ml at the 36th week (P< 0.0001). hANP correlated with MAP in the NT group (r = 0.252, P< 0.0005) but not the PIH group. U-Ald in the NT group increased from 23.52 +/- 6.83 microg/24 h at the 8th week to 54.07 +/- 19.62 microg/24 h at the 36th week (P < 0.0001) and in the PIH group it increased from 27.90 +/- 11.6 to 53.66 +/- 20.4 microg/24 h (P< 0.0001). In the PIH group, PRA was lower compared with the NT group from the 8th (2.99 +/- 1.26 versus 4.10 +/- 1.82 ng/ml per h, P< 0.05) until the 36th week (3.34 +/- 2.16 versus 4.46 +/- 2.13 ng/ml per h). In the forced multiple regression analysis model with hANP as a dependent variable, a value of P< 0.003 was found with PRA, U-Ald and MAP, which indicates an interaction between the two vasoactive and homeostatic systems: the renin-angiotensin-aldosterone system and hANP.

CONCLUSIONS

In PIH, elevated hANP might be important as a counterbalance to the presence of the active vasopressors and sodium retention. By inhibiting renin release, enhancing the transcapillary fluid migration and with its action as vasodilator, it acts as a corrective factor of the imbalance between the contracted circulating fluid volume and the vasoconstricted vascular bed.

Atrial natriuretic peptide in aged patients with iron deficiency anemia

Anemia is a common disease in elderly people. However, since hemoglobin concentration often decreases subclinically with aging because of nutritional impairment, its pathological significance is unclear. To investigate the pathological significance of low hemoglobin concentration, we studied the relation between hemoglobin levels and arrhythmia, as well as circulatory parameters. Arrhythmia was detected by Holter type ambulatory electrocardiography in 42 elderly people (aged 60 or over) living in a nursing home. Plasma concentrations of human atrial natriuretic peptide (hANP) after iron therapy were determined by immunoradiometric assay. Changes in circulatory parameters in elderly people with iron deficiency anemia were examined. Supraventricular and ventricular premature contractions significantly increased in elderly people with low hemoglobin concentrations or hematocrit. hANP increased significantly as the hemoglobin concentration decreased in 22 elderly people. Of these 22 subjects, 11 showed a low serum concentration of iron, and were administered ferrous salts. No side effects, such as nausea, occurred. After iron supplementation, the average hemoglobin level increased from 9.0 to 10.5 g/dl, and the average hANP level was reduced from 58.3+/-23.5 to 41.2+/-27.9 pg/ml, which was statistically significant by Wilcoxon's signed rank sum test. The increase in the hemoglobin level inversely correlated with the hANP level. Heart rate, blood pressure and body weight of subjects decreased significantly after iron supplementation therapy. Although hemoglobin levels were increased by iron supplementation therapy after a long period of anemia, the duration of the period with low hemoglobin levels showed no significant relation to initial hANP concentration. In conclusion, low hemoglobin levels induced secretion of hANP, and treatment of iron deficiency might exert favorable effects on the circulatory system.

Beneficial effect of atrial natriuretic peptide on pulmonary gas exchange in patients with acute lung injury

STUDY OBJECTIVES

The purpose of this study was to investigate the effect of i.v. infusion of atrial natriuretic peptide (ANP) on hemodynamics, pulmonary gas exchange, and urine volume during mechanical ventilation with positive end-expiratory pressure (PEEP) in patients with acute lung injury.

DESIGN

Prospective, randomized, comparable study.

SETTING

ICU of a university hospital.

PATIENTS

Forty patients with moderate acute lung injury (lung injury score > or = 2.0) who required mechanical ventilation with PEEP were studied.

INTERVENTIONS

The patients were randomly divided into two groups: ANP group (n=20) and control group (n=20). The ANP group received genetic recombination alpha-human ANP (carperitide) at the rate of 0.1 microg/kg/min for 24 h. The control group did not receive ANP.

MEASUREMENTS AND RESULTS

Hemodynamic and blood gas parameters, and urine volume were measured at baseline, 3 h, and 24 h after initiating the ANP infusion. Plasma ANP concentrations markedly (p<0.01) increased from 112.0+/-27.0 to 1,868.3+/-385.3 pg/mL after 24 h in the ANP group, whereas they remained unchanged in the control group. In the ANP group, hemodynamic parameters did not change, but PaO2/FIO2 (fraction of inspired oxygen) and thoracic compliance significantly (p<0.01) increased at 24 h after initiating the ANP infusion, associated with significant (p<0.01) decreases in lung injury score and shunt. Urine volume significantly (p<0.01) increased during 0 to 3 h after initiating the ANP infusion. In the control group, hemodynamics, pulmonary gas exchange, and urine volume did not significantly change during the study period. There were significant differences in PaO2/FIO2 (24 h), thoracic compliance (24 h), lung injury score (24 h), and urine volume (3 h) between the two groups.

CONCLUSION

The results suggest that ANP infusion induces diuresis and improves pulmonary gas exchange in patients with acute lung injury during mechanical ventilation with PEEP.

Increased plasma concentrations of brain natriuretic peptide in patients with acute lung injury

PURPOSE

This study was performed to elucidate the pathophysiological role of brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) in acute lung injury.

MATERIALS AND METHODS

We sequentially measured plasma concentrations of immunoreactive BNP and ANP in 10 patients (mean age, 63 years (with acute lung injury and compared those with hemodynamic parameters and pulmonary functions.

RESULTS

Plasma concentrations of immunoreactive BNP and ANP were markedly elevated at entry into the study. Plasma BNP concentrations during the early course (3 days) showed significant (P < .01) positive correlations with systemic vascular resistance index (r = .708) and pulmonary vascular resistance index (r = .573), but a negative correlation with cardiac index (r = .608). Plasma ANP concentrations showed a significant (P < .05) positive correlation with pulmonary capillary wedge pressure (r = .398). Plasma BNP in 4 patients who died and 1 patient with acute renal failure remained elevated during the entire hospital length of stay (12 days).

CONCLUSION

These findings suggest that circulating BNP plays an important role in acute lung injury along with ANP as a compensatory mechanism for cardiac dysfunction accompanied by increased systemic vascular resistance index and pulmonary vascular resistance index. Circulating BNP may be a sensitive humoral marker for the degree of ventricular dysfunction associated with acute lung injury.

Early changes in plasma brain and atrial natriuretic peptides in premature infants: correlation with pulmonary arterial pressure

To define the change in plasma natriuretic peptides in newborns, we prospectively studied 10 premature infants. They were followed sequentially during the first week of extrauterine life by two-dimensional and pulsed Doppler echocardiography, and studied for atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). We estimated mean pulmonary arterial pressure (MPAP) and measured blood pressure on days 1, 2, 3, 5, 7, respectively. Plasma ANP levels were 81.7 +/- 11.4 pg/ml on day 1 and 67.9 +/- 6.0 pg/ml on day 7, respectively. Between day 2 and day 7, there was a fall in MPAP, i.e. from 37 +/- 4 mmHg to 22 +/- 2 mmHg (P < 0.01), which was associated with a significant decrease in plasma BNP (41.8 +/- 10.1 pg/ml on day 2 vs. 10.4 +/- 0.9 pg/ml on day 7, P < 0.01). There was a positive correlation between MPAP and plasma BNP level (r = 0.643, P < 0.0001), but there was no correlation between MPAP and plasma ANP level. These data suggest that the pattern of secretion of BNP is different from that of ANP and that BNP levels reflect the changes of pulmonary arterial pressure in the neonatal period in premature infants.

Effects of posture on the plasma hormonal and renal water-electrolyte excretory responses to acute water loading in diabetic subjects with hypoadrenergic orthostatic hypotension

The effects of posture on the plasma hormonal and renal water-electrolyte excretory responses to acute water loading (20 mL/kg BW, orally) were studied in six non-insulin-dependent diabetes mellitus (NIDDM) subjects with hypoadrenergic orthostatic hypotension (HOH), eight NIDDM subjects without HOH, and seven nondiabetic subjects. The three groups were similar with respect to basal levels of mean blood pressure (MBP), serum sodium and osmolality, plasma renin activity (PRA), the plasma volume regulatory hormones alpha-atrial natriuretic peptide (ANP), arginine vasopressin (AVP) and aldosterone, and urinary water and sodium excretion. In the supine state, while allowing the subjects to stand only to void, water loading resulted in no changes in MBP and similar responses of these plasma and urinary parameters in the three groups. In the standing state, water loading produced responses of MBP, and plasma and urinary parameters comparable to those in the supine state in the diabetic group without HOH and the nondiabetic group. In the diabetic group with HOH, however, MBP and hourly urinary water and sodium excretion rates were low compared to those in the other two groups. During water loading, plasma ANP decreased, and, despite the fall of MBP, plasma AVP remained unchanged, and PRA and plasma aldosterone increased normally in the diabetic group with HOH. These results demonstrate that, in NIDDM subjects with HOH, changing from lying to standing induces deranged renal water and sodium handling after water loading, accompained by a decrease in plasma ANP, and inadequate responses of plasma AVP, PRA, and plasma aldosterone to hypotension.

Right ventricular function and plasma atrial natriuretic peptide levels during fiberbronchoscopic alveolar lavage in critically ill, mechanically ventilated patients

STUDY OBJECTIVE

To assess the influence of fiberbronchoscopic alveolar lavage on hemodynamics, right ventricular function, and plasma atrial natriuretic peptide (ANP) concentrations in critically ill, mechanically ventilated patients.

DESIGN

Prospective investigation.

SETTING

Eight-bed ICU of a university hospital.

PATIENTS

Fourteen patients with cardiovascular instability due to a systemic inflammatory response syndrome who were mechanically ventilated.

INTERVENTIONS

Fiberbronchoscopic alveolar lavage after fluid replacement, deep sedation, and paralyzation. Intervention time: 10 min. After inspection of the endobronchial system, one lavage of 40 mL sterile saline solution was instilled in each lung and recovered.

MEASUREMENTS AND RESULTS

The fiberbronchoscopic procedure induced a prompt increase in mean pulmonary arterial pressure after 3 min (median[range]: 25 [13 to 39] to 30 [19 to 45] mm Hg, p < 0.05), which increased further after 6 min (34 [17 to 46] mm Hg, p < 0.01). Cardiac index increased simultaneously (4.25 [3.1 to 5.7] to 4.85 [4.3 to 6.9] L/min.m2 after 6 min, p < 0.01), whereas mean arterial pressure and heart rate remained unchanged. Central venous pressure rose from 12 (3 to 18) mm Hg before procedure to 14 (4 to 20) mm Hg after 6 min (p < 0.01). The right ventricular function was measured using a "fast response" ejection fraction thermodilution catheter: end-diastolic volume increased (238 [137 to 358] to 280 [150 to 4ll] mL after 9 min, p < 0.05), as well as stroke volume (88 [54 to 113] to 103 [67 to 153] mL after 9 min, p < 0.01). Right ventricular ejection fraction (37 [25 to 50] %) did not change significantly during the procedure, but the stroke work index was reinforced (8.2 [4.7 to 15.7] to 13.3 [2.4 to 41.3] gm.M/M2 after 6 min, p < 0.01). Plasma c-ANP concentration rose from 135 (24 to 350) to 196.5 (44 to 830 pg/ml after 20 min (p < 0.05). Systemic vascular resistance decreased from 533 (390 to 1,042) to 429 (281 to 684) dynes.s/cm5 after removal of the bronchoscope (p < 0.01).

CONCLUSIONS

Although acute pulmonary hypertension was observed during the fiberbronchoscopic procedure, the right ventricular performance did not deteriorate in hemodynamically unstable patients. To maintain a "hyperdynamic cardiovascular state," the right ventricular stroke work was reinforced, presumably by the "Frank-Starling mechanism." We assume that the acute distention of the right side of the heart resulted in elevated ANP concentrations. The marked decrease in systemic vascular resistance might be due to high ANP levels.

Release of urodilatin from perfused rat kidney and from cultured neonatal rat kidney cells

Release of rat urodilatin (rURO) from isolated perfused rat kidneys and neonatal rat kidney cells could be demonstrated by a specific competitive radioimmunoassay (rURO-RIA) using [125I]rURO as the competitive antigen and an antiserum against the hypothetical rURO-N-terminus, Ala-Gly-Pro-Arg, as concluded from the amino acid sequence of the rat prohormone CDD/ANP-1-126. This antiserum did not react with synthetic rCDD/ANP-99-126, brain natriuretic peptide (BNP), C-type natriuretic peptide (CNP), or human URO (hURO). rURO could be demonstrated in the urine of the perfused rat kidney after an equilibration period of 20 min. After an initial slight decrease in the second 20 min, rURO production remained at almost the same level during the perfusion time of 100 min. A total of approximately 470 fmol.10 -1.g-1 kidney rURO was produced within 80 min. rURO was also produced by neonatal rat kidney cells kept in serum-free Dulbecco's modified Eagles medium. The production of rURO depended on the cultivation time of the cells. It increased up to 3 days reaching 239 +/- 7.5 fmol.h-1.g-1 protein, afterwards it decreased rapidly. The results obtained indicate that the rat kidney produces a peptide of the type A family of natriuretic peptides, which very likely represents the putative rURO.

Attenuation of atrial natriuretic peptide response to sodium loading after cardiac operation

To evaluate the role of cardiac operation and the atrial appendage in secretion of atrial natriuretic peptide in response to sodium loading, we studied 44 patients who underwent heart operations with (28 patients; group I) or without (16 patients; group II) right atrial appendectomy and 16 patients who underwent lobectomy (group III). Before and after operation 1 ml/kg of 10% NaCl was infused for 15 minutes. Blood samples were taken before NaCl infusion and immediately after infusion and at 60 minutes after infusion. There were no significant changes in hemodynamics or hematocrit level throughout the study. Plasma and urine sodium levels and the fractional excretion of sodium were significantly increased by sodium loading. Before operation, plasma mean atrial natriuretic peptide levels increased markedly in response to sodium infusion in all groups. After operation, this atrial natriuretic peptide response disappeared in groups I and II, but remained present in group III. Elution profiles of plasma atrial natriuretic peptide showed that the major peak coincided with alpha-atrial natriuretic peptide before sodium loading, whereas a beta-atrial natriuretic peptide peak appeared 60 minutes after sodium loading in all groups both before and after operation. The mean plasma arginine vasopressin levels were significantly increased by sodium loading both before and after operation in all groups. Sodium loading decreased the mean plasma aldosterone levels in all groups before operation, but did not after operation in groups I and II. Plasma renin activity and angiotensin II concentrations were not changed by sodium loading. We conclude that atrial natriuretic peptide response to sodium loading is attenuated by cardiac operation irrespective of right appendectomy, but not by lobectomy. Sodium loading augments secretion of beta-atrial natriuretic peptide even in reduced atrial natriuretic peptide response states after heart operations.

Changes in molecular pattern of atrial natriuretic peptide in hemodialysis patients

An attempt was made to clarify whether the molecular forms of atrial natriuretic peptide (ANP) in the plasma of stable hemodialysis patients differ from those of healthy volunteers, and whether the ANP molecular forms in plasma might change during hemodialysis treatment. Ten stable hemodialysis patients with no clinical signs of cardiac disease were treated for 4 hours by a hollow fiber-type dialyzer. Plasma ANP concentrations before dialysis were 210 ± 101.6 pg/ml (mean ± SD), which were significantly higher than that of volunteers (59.2 ± 37.2 pg/ml, n=25). They were significantly decreased to 71.6 ± 60.1 pg/ml after dialysis. Molecular patterns of ANP were measured by gel permeation chromatography and reverse-phase high performance liquid chromatography. Immunoreactive alpha-ANP peaks of GPC, which co-migrated with authentic alpha-, beta-, and gamma-ANP, were supposed to be alpha-, beta-, and gamma-ANP. The plasma of four patients contained a beta-ANP peak before dialysis, and three of the four still contained a beta-ANP peak after dialysis. These results showed that the middle-molecular-weight ANP, which co-migrated with authetic beta-ANP and is supposed to be beta-ANP, may particularly be secreted in clinically stable hemodialysis patients.

Atrial natriuretic peptide response to unilateral pulmonary artery occlusion

To test the hypothesis that neural mechanisms evoked by unilateral pulmonary artery occlusion (UPAO) affect the release of atrial natriuretic peptides (ANP) from the heart, hemodynamics and levels of plasma ANP and cyclic guanosine monophosphate (c-GMP) were studied in 11 patients with lung cancer. The UPAO induced a significant rise in heart rate by 5.3 percent, increased mean pulmonary artery pressure by 31 percent without affecting right atrial pressure, and decreased plasma ANP levels in the coronary sinus by 17.4 percent (p < 0.05) from 202.5 +/- 27.1 pg/ml to 167.2 +/- 27.4 pg/ml. Atropine sulfate (0.04 mg/kg) injection increased the heart rate by 38.2 percent (p < 0.01), reduced the stroke volume index by 25.1 percent, decreased coronary sinus ANP levels from 198.5 +/- 16.4 pg/ml to 124.8 +/- 19.6 pg/ml (p < 0.01), and decreased coronary sinus plasma c-GMP levels from 4.6 +/- 0.5 pmol/ml to 3.1 +/- 0.4 pmol/ml (p < 0.05). After atropine pretreatment, UPAO induced a significant (p < 0.05) increase of 34.8 percent in the coronary sinus ANP level. Thus, it is concluded that in UPAO, the secretion of ANP from the heart is modulated partly by the autonomic nervous system.

Alterations in plasma concentrations of natriuretic peptides and antidiuretic hormone after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Hyponatremia is a common complication after subarachnoid hemorrhage. In this study we investigated the relations among hyponatremia, plasma natriuretic peptides, and antidiuretic hormone concentrations after subarachnoid hemorrhage.

METHODS

Blood samples for radioimmunoassay measurement of plasma brain natriuretic peptide-like immunoreactivity, atrial natriuretic peptide-like immunoreactivity, and antidiuretic hormone were obtained every 2 to 4 days until day 14 after subarachnoid hemorrhage.

RESULTS

Eleven of 20 patients with verified subarachnoid hemorrhage demonstrated mild hyponatremia (126 mEq/L < serum sodium < 135 mEq/L) during their clinical course. Atrial natriuretic peptide and antidiuretic hormone concentrations were significantly elevated on days 0 to 2 after onset of subarachnoid hemorrhage. Atrial natriuretic peptide concentrations remained high in patients who developed mild hyponatremia on days 6 to 14 after onset of subarachnoid hemorrhage. In contrast, antidiuretic hormone concentrations became significantly lower during the second week in these patients.

CONCLUSIONS

Mild hyponatremia after subarachnoid hemorrhage may be attributable not to the syndrome of inappropriate secretion of antidiuretic hormone but to cerebral salt-wasting syndrome. Atrial natriuretic peptide may be a causal natriuretic factor in cerebral salt-wasting syndrome.

Plasma concentration of human atrial natriuretic hormone in patients with connective tissue diseases

Atrial natriuretic peptide (ANP), a peptide released from the cardiac atria, compensates blood volume expansion by its diuretic, natriuretic and vasoactive properties. We measured human plasma ANP(hANP) levels in patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and progressive systemic sclerosis (PSS) and found that their values were higher than those of healthy controls. In SLE patients, hANP levels correlated with serum creatinine concentration and the patients with proteinuria showed high levels of hANP. Administration of large amount of corticosteroid as a remission induction of the patients with SLE caused high levels of hANP. In patients with PSS, %FEV1 showed strong inverse correlations between hANP levels, and the patients with an enlarged second curvature of the heart had high levels of hANP. In patients with RA, no significant correlation was found between hANP levels and clinical variables including patients' age.

L-arginine infusion induces hypotension and diuresis/natriuresis with concomitant increased urinary excretion of nitrite/nitrate and cyclic GMP in humans

1. The vascular endothelium produces endothelium-derived relaxing factor (EDRF) or nitric oxide (NO), which exerts vasodilation through cyclic guanosine monophosphate (cGMP) as a second messenger. To determine whether EDRF has any vasodilating and natriuretic action in man, the present study examined the effects of L-arginine (L-Arg), a substrate for NO, on the responses of mean blood pressure (MBP) and heart rate (HR); plasma concentrations of cGMP, atrial natriuretic factor (ANF) and nitrite/nitrate (NOx); urinary excretion of sodium, cGMP and NOx; and urinary flow in eight normal male subjects. These parameters were compared with those following saline infusion in the same subjects. Clearance of para-aminohippuric acid (PAH) and inulin was studied in five normal subjects. 2. Infusion of L-Arg (30 g) caused a significant fall in MBP (-8 mmHg) with a concomitant rise in HR (10 beats/min), while saline infusion had no effects on these parameters. 3. Neither L-Arg nor saline infusion caused appreciable changes in plasma concentrations of ANF or NOx. Plasma cGMP concentrations increased significantly during (1.7-fold) and after (1.9-fold) L-Arg infusion, but only slightly (1.3-fold) during saline infusion. 4. Urine flow increased more remarkably following L-Arg infusion than that following saline infusion. Remarkable increases in urinary excretion of sodium and fractional excretion of sodium were observed after L-Arg infusion compared with those after saline infusion. Natriuresis was associated with enhanced urinary excretion of cGMP and Nox. Urinary Nox excretion showed positive correlations with urinary flow (r = 0.69, P less than 0.001) and with urinary cGMP excretion (r = 0.60, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical significance of elevated plasma endothelin concentration in patients with cirrhosis

Endothelin is a newly discovered potent vasoconstrictor peptide. To explain the clinical significance of endothelin in patients with chronic liver diseases, we measured the plasma concentration of endothelin in patients with chronic hepatitis (n = 15), cirrhosis with ascites (n = 8) and cirrhosis without ascites (n = 12), and we compared the findings with the plasma concentration of endothelin in normal controls (n = 14). The plasma endothelin concentration was significantly higher in patients with cirrhosis with ascites than in normal controls (8.3 +/- 2.3 pg/ml vs. 3.3 +/- 1.4 pg/ml, mean +/- S.D., p less than 0.001), whereas no significant difference was observed between normal controls and the other groups of patients (cirrhosis without ascites = 5.0 +/- 1.3 pg/ml; chronic hepatitis = 3.8 +/- 1.2 pg/ml). In patients with cirrhosis, the plasma endothelin concentration showed a significant negative correlation with creatinine clearance (r = -0.73, p less than 0.01), but no significant correlation was observed between plasma endothelin concentration and fractional excretion of filtered sodium. Furthermore, plasma endothelin levels were significantly higher in patients with endotoxemia than in those without (10.1 +/- 2.1 pg/ml vs. 4.9 +/- 1.2 pg/ml, p less than 0.001). From these results, elevated plasma endothelin, which has a close relation to endotoxemia, may play a contributory role in kidney dysfunction in patients with cirrhosis.

Kinetics of atrial natriuretic peptide in young and elderly subjects

To study the influence of age on the kinetics of atrial natriuretic peptide (ANP) in man, human (99-126) ANP 2.0 micrograms.min-1 was infused IV for 60 min in 8 healthy young (18 to 25 y) and 9 healthy elderly (71 to 84 y) subjects. Both baseline ANP values and the levels at the end of infusion were higher in the elderly subjects. The mean residence time of ANP in the two age groups was not significantly different, whereas total body clearance (CL) was markedly diminished in the elderly as compared to the young subjects (mean +/- SD 3.1 +/- 1.0 l.min-1 and 6.2 +/- 4.1 l.min-1, respectively). The apparent volume of distribution at steady state was lower in the elderly than in the young, but the difference was not significant (mean +/- SD 44 +/- 19 and 103 +/- 111, respectively. The decrease in CL largely explained the higher ANP levels found in the elderly subjects. The MRT and the plasma half-life of the terminal phase did not differ between the two groups. In the elderly but not in the young subjects the calculated endogenous creatinine clearance was closely correlated with the CL (r = 0.90, P less than 0.001), thereby emphasizing the importance of the kidney in the metabolic clearance of ANP in the elderly.

Brain natriuretic peptides in human plasma, spinal cord and cerebrospinal fluid

In cases of heart failure, the plasma level of immunoreactive human brain natriuretic peptide (IR-hBNP) measured by radioimmunoassay increased 6- to 46-fold over normal level (4.1 +/- 1.0 pg/ml), depending upon the severity. These levels did not significantly correlate to the levels of IR-human atrial natriuretic peptide in individuals. A 4-kDa IR-hBNP, corresponding to authentic hBNP (1-32), was predominant in normal plasma. In cases of cardiac disease, larger molecules which were assumed to be precursors of the 4-kDa form were accumulated in plasma. IR-hBNP was detected in spinal cords (7-24 pg/mg protein) and cerebrospinal fluid (8-19 pg/ml) of patients with noncardiac diseases. The major molecular form corresponded to the hBNP (1-32).

Pulmonary and urinary clearance of atrial natriuretic factor in acute congestive heart failure in dogs

Atrial natriuretic factor (ANF) is a peptide hormone of cardiac origin elevated in acute congestive heart failure (CHF), which is degraded by the enzyme neutral endopeptidase 24.11 (NEP). This study was designed to investigate the pulmonary and urinary clearance of ANF before and after the initiation of acute experimental CHF in dogs, and to assess the contribution of enzymatic degradation to these clearances in CHF. This study demonstrated a significant clearance of plasma ANF across the pulmonary circulation at baseline, and a tendency for pulmonary clearance to decrease in CHF (1115 +/- 268 to 498 +/- 173 ml/min, NS). The pulmonary extraction of ANF present at baseline was not altered with acute CHF (36.0 +/- 7.8 to 34.9 +/- 12.1%, NS). NEP inhibition (NEPI) abolished both the clearance and extraction of plasma ANF across the lung in CHF. Similarly, significant urinary clearance of ANF was present at baseline, and in acute CHF the urinary clearance of ANF decreased (0.14 +/- 0.02 to 0.02 +/- 0.01 ml/min, P less than 0.05). NEPI prevented the decrease in the urinary clearance of ANF, and enhanced the renal response to endogenous ANF, independent of further increases in plasma ANF during CHF. This study supports an important role for NEP in the pulmonary and urinary metabolism of endogenous ANF during acute CHF.

Combination of high-performance liquid chromatography and radioimmunoassay for the measurement of urodilatin and alpha-hANP in the urine of healthy males

Urodilatin (ANP-(95-126)), a natriuretic peptide in urine, and alpha-hANP (ANP-(99-126)) are crossreactive in the radioimmunoassay of alpha-hANP (ANP-RIA). We therefore developed a method to separate physiological amounts of urodilatin and alpha-hANP in urine by high-performance liquid chromatography (HPLC) followed by ANP-RIA of the separated fractions. We studied urine samples of 10 healthy adult males with a plasma alpha-hANP level of 41 +/- 21 pg/ml (mean +/- SD) and a total urinary ANP-RIA reactivity of 40 +/- 21 pg/ml. In all urine samples we found three peaks of ANP-RIA reactivity, the first one coeluting with synthetic urodilatin, the second one with the retention time of alpha-hANP and a late eluting ANP-RIA-reactive peak, possibly containing degradation products. The ratio of urodilatin/alpha-hANP was 0.77 +/- 0.17.

Synthesis and secretion of an atriopeptin-like protein in rat kidney cell culture

The synthesis and secretion of an atriopeptin(AP)-like prohormone (AP126ir) has been demonstrated in rat neonatal renal cell cultures. AP126ir could be detected in the cellular extract and the medium from cultured kidney cells of neonatal and adult rats using an enzyme immunoassay specific for cardiac AP prohormone. On reverse-phase high-performance liquid chromatography, the AP obtained from the extract and the medium comigrated with cardiac AP prohormone. Incubation of the renal AP in the medium with thrombin resulted in the generation of a single low molecular mass peak which migrated with the cardiac carboxy-terminal 28-amino acid AP. Neonatal kidney cells pulsed with [35S]methionine secreted radiolabeled AP126ir, which was detected by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis chromatography. Incubation of neonatal kidney cell cultures with the protein synthesis inhibitor cycloheximide resulted in a significant decrease in both the cellular and media AP. No decrease in cellular and media AP was detected when neonatal atrial cultures were treated with cycloheximide. These data demonstrate the de novo synthesis of an AP prohormone-like protein in neonatal rat kidney cultures. Furthermore, unlike the atria, kidney cells appear to secrete AP solely by constitutive means. In primary adult rat kidney cultures, most of AP126ir was detected in the cortical tubule fraction demonstrating that these cells secrete AP126ir in the adult rat kidney. We hypothesize that the renal AP may be important as an autocrine or paracrine regulator of renal function.

Atrial natriuretic peptide in the dog with mitral regurgitation

The concentration and molecular form of the plasma atrial natriuretic peptide (ANP) in dogs with mitral regurgitation was investigated. Plasma ANP concentration in dogs with mitral regurgitation was significantly increased (29.4 +/- 1.88 pmol litre-1, n = 40) compared to that in the controls (14.5 +/- 0.62 pmol litre-1, n = 20, P less than 0.01). Molecular forms of plasma ANP were determined by the gel permeation chromatogram. A single peak corresponding to alpha-ANP was detected in the plasma from the controls. However, a peak corresponding to beta-ANP and, or, gamma-ANP was detected in the plasma of the dogs with mitral regurgitation in addition to alpha-ANP. These results suggest that the process of ANP synthesis was altered and excretion of ANP from the heart was enhanced in dogs with mitral regurgitation.

The N-terminus, C-terminus, and vessel dilator of the ANF prohormone are present in the urine and increase with ventricular fibrillation

The N-terminus consisting of amino acids (a.a.) 1-98 (i.e., proANF 1-98), C-terminus (i.e., ANF; a.a. 99-126) and midportion of N-terminus consisting of a.a. 31-67 (proANF 31-67; Vessel Dilator) of the 126 a.a. ANF prohormone were present in the urine in 5-to-8-fold increased concentrations versus their plasma concentrations in 6 dogs under basal conditions. With acute coronary occlusion the right atrial plasma concentrations of these peptides increased two-to-three-fold, while in the urine only proANF 31-67 increased (3.5-fold). Ventricular fibrillation caused a 4-to-10-fold increased secretion into the right atrial chamber with a simultaneous 3-to-4.7-fold increase in the urine of proANF 1-98, proANF 31-67, and ANF. This investigation demonstrates that proANF 1-98, proANF 31-67 and ANF are normally present in urine and increase in the urine with cardiac stimuli that cause their release from the heart.

Effects of continuous negative extrathoracic pressure ventilation on renal function and alpha-atrial natriuretic peptide in normal individuals

Continuous negative extrathoracic pressure ventilation (CNETPV) may induce atrial distention by augmenting venous return, resulting in the increased secretion of atrial natriuretic peptide (ANP) and natriuresis. To clarify this hypothesis, we investigated the effect of CNETPV on renal function and plasma ANP level. Nine male healthy volunteers were studied during three successive 60-minute periods under (1) spontaneous breathing, (2) CNETPV with continuous negative extrathoracic pressure of -10 cm H2O, and (3) spontaneous breathing again. Continuous negative extrathoracic pressure ventilation induced a transient increase in plasma ANP level, but changes in plasma ANP level were not statistically significant. Although there was no significant difference in urine volume and urinary sodium excretion among three successive periods, a slight but significant increase in creatinine clearance was noticed during CNETPV. These results indicate that CNETPV with continuous negative extrathoracic pressure of -10 cm H2O does not induce the major change in ANP secretion and renal function in normal subjects.

Immobilization of alpha-human atrial natriuretic peptide on insoluble supports and affinity purification of specific antibodies from a polyclonal goat anti-alpha-human atrial natriuretic peptide serum

alpha-Human atrial natriuretic peptide (alpha-hANP) was covalently coupled via single attachment onto two different insoluble matrices. Controlled-pore glass-alpha-hANP matrices were well suited for the purification of monospecific antibodies, whereas Enzacryl AA-alpha-hANP did not withstand the inevitable chemical and physical stresses during affinity purification.

Plasma endothelin levels in hypertension and chronic renal failure

Endothelin-1 is a novel endothelium-derived vasoconstrictive peptide. Using a highly specific and sensitive radioimmunoassay for endothelin-1, plasma levels of immunoreactive endothelin-1 were measured in 32 research subjects with normal renal function (21 normal subjects and 11 patients with essential hypertension), 24 patients with nondialyzed chronic renal failure, and 51 patients undergoing maintenance hemodialysis. Although there was no significant difference in plasma immunoreactive endothelin-1 levels among the three groups, patients with essential hypertension had significantly higher plasma endothelin-1 levels than normal subjects (2.29 +/- 1.09 vs. 1.41 +/- 0.50 pg/ml, p less than 0.025). When nondialyzed and hemodialyzed patients were divided into hypertensive and normotensive groups, the nondialyzed hypertensive group (n = 17) had higher plasma endothelin-1 levels than the comparable normotensive group (n = 7) (3.08 +/- 3.43 vs. 0.73 +/- 0.34 pg/ml, p less than 0.05), and the hemodialyzed hypertensive group (n = 18) had higher plasma endothelin-1 levels than the comparable normotensive group (n = 33) (2.66 +/- 1.92 vs. 1.35 +/- 0.73 pg/ml, p less than 0.005). Plasma atrial natriuretic factor, arginine vasopressin, renin activity, and aldosterone concentration did not show significant differences between hypertensive and normotensive individuals or a correlation with plasma endothelin-1 levels. These data suggest that circulating endothelin-1 may be partly involved in the development or maintenance of hypertension in humans.

Hemodynamic changes by recombinant erythropoietin therapy in hemodialyzed patients

Recombinant human erythropoietin therapy was given to 15 patients undergoing long-term hemodialysis with normal cardiac function. None of the patients had hypertension before the erythropoietin therapy and had received no antihypertensive agents. Before and after the erythropoietin therapy M-mode and pulsed Doppler echocardiographic studies, measurements of plasma volume by radioiodinated human serum albumin, and measurements of atrial natriuretic factor were carried out. After 6 weeks of erythropoietin therapy, hematocrit increased from 20.0 to 33.0%. Cardiac output, stroke volume, left ventricular diastolic dimensions, and left ventricular wall stress were all significantly decreased. Total peripheral resistance, interventricular septal thickness, and left ventricular posterior wall thickness were significantly increased. In Doppler echocardiographic studies, the mean velocity of aortic ejection flow and left ventricular acceleration time were decreased. The blood volume derived from plasma volume and hematocrit was not changed, whereas plasma atrial natriuretic factor concentration was significantly decreased. These data suggest that recombinant human erythropoietin administration suppressed the hyperdynamic cardiac state that was required to maintain oxygen delivery to the peripheral tissues in severe uremic anemia.

Presence of immunoreactive atrial natriuretic peptides in pericardial fluid of human subjects with congenital heart diseases

The epicardial release of immunoreactive atrial natriuretic peptides (ir-ANPs) in inside-out perfused rabbit atria has been reported. In order to determine the presence of ir-ANPs in pericardial fluid and to evaluate their biochemical characteristics, we measured the concentration of ir-ANPs in pericardial fluid obtained from the patients with congenital heart diseases during open heart surgery. Serial dilution curves made with the extrats of pericardial fluid using Sep-Pak C18 cartridges were parallel with standard curve. The concentration of ir-ANPs in pericardial fluid was significantly lower than the corresponding plasma concentration. On gel permeation and reverse-phase high performance liquid chromatography, the ir-ANPs in pericardial fluid, plasma and atrial appendage showed both high and low molecular weights. The major peak of ir-ANPs in plasma was observed at the corresponding fraction to the alpha-human ANP and considerable amount of high molecular weight form of ir-ANPs was observed in pericardial fluid. However, the major peak of ir-ANPs in atrial appendage was observed at the corresponding fraction to the rat pro-ANP. The data suggest that ir-ANPs exist both high and low molecular weight forms in pericardial fluid.

The physiological and biological significances of human atrial natriuretic peptide in neonates

The purpose of our study was to analyze the physiological and biological significances of the high human atrial natriuretic peptide (hANP) levels during early post-natal period. The absolute values or changes of plasma hANP concentrations did not correlate with the absolute values or changes of body weight, blood pressure, urinary sodium/creatinine and urinary aldosterone/creatinine ratios. Gel permeation chromatography of samples from two neonates revealed the presence of two molecular forms of hANP, alpha and beta, both in the plasma and urine. In the plasma, the beta-hANP was predominant on the 3rd day of life and the alpha-hANP on the 6th day of life. The change from one form to another was independent of the absolute value of hANP. We obtained no evidence suggestive of a physiological role of the high plasma hANP concentration during the early post-natal period. However, because of biological differences between these two fractions, their distribution must be taken into account when attempting to interpret the high hANP values observed in neonates.

Degradation and clearance of atrial natriuretic factors (ANF)

Atrial natriuretic factor, the first well defined natriuretic hormone is synthesized in the human heart as 151 aminoacid (AA) preprohormone and stored as 126 AA prohormone in atrial granules. Upon appropriate stimulation, the prohormone is cleaved into a 98 AA N-terminal fragment and a 28 AA C-terminal fragment, the biological active ANF(99-126), both circulating in plasma. Circulating ANF(99-126) is cleared by various organs, such as lung, liver and intestine, kidney and upper and lower limbs. Reported arterial-venous extraction ratios vary greatly, but are not much different between organs, the average extraction ratio being about 35%. Due to marked differences of organ blood flow, the contribution of various organs to total body ANF clearance differs considerably. Major mechanisms for ANF clearance are uptake by clearance receptors and degradation by an endoprotease (EC 3.4.24.11.). Clearance receptors, distinct from the receptors mediating the biological actions of ANF, have been demonstrated in various organs. Characterization of the ANF degrading enzyme activity has been performed in kidney tissue. Whether and how pathophysiological states affect ANF clearance is still poorly understood. Inhibition of clearance by ANF analogues binding to clearance receptors and by inhibitors of degrading peptidase can increase the biological action of circulating ANF. This may prove to be a therapeutic approach in diseases with smooth muscle contraction or volume overload.

Enkephalinase (EC 3.4.24.11) inhibitors: protection of endogenous ANF against inactivation and potential therapeutic applications

Atrial natriuretic factor (ANF) is a cardiac hormone exerting potent cardiovascular and renal effects but its poor intestinal absorption and rapid inactivation have prevented so far its therapeutic utilisation. However inhibition of endogenous ANF metabolism progressively emerges as a novel therapeutic approach in cardiovascular and renal disorders. The critical role played by enkephalinase (membrane metalloendopeptidase, EC 3.4.24.11) in ANF inactivation was deduced from the effects of inhibitors. These compounds not only protect partially exogenous ANF from hydrolysis by some tissue preparations in vitro but also, in vivo, they increase the half-life of the exogenous hormone in plasma and, even more markedly, its recovery in intact form in kidney, a major target organ. In addition, enkephalinase inhibitors increase by two- to three-fold the circulating level of endogenous ANF, even when the latter is already markedly elevated, such as in patients with chronic heart failure. Finally, enkephalinase inhibitors induce a series of ANF-like responses such as natriuresis, diuresis or increase in cGMP excretion which are attributable to the hormone. These pharmacological observations, as well as preliminary clinical trials, suggest that enkephalinase inhibitors may represent a novel class of therapeutic agents with potential applications in congestive heart failure, essential hypertension and various sodium-retaining states.

Ratio between aldosterone and atrial natriuretic peptide in pregnancy

The possibility of evaluating the ratio between aldosterone and atrial natriuretic peptide (ANP) instead of the two hormones by themselves in studying sodium handling in normal pregnancy and in preeclampsia in the steady state and following albumin infusion was examined in this study. In 32 normal pregnancies monitored monthly, the highest aldosterone/ANP ratio was observed in the last weeks (28.7 +/- 12), and dropped in the first postpartum week (3.6 +/- 2.8), without changes in fractional excretion of sodium. In 18 preeclamptic patients, the ratio was significantly lower than in normal pregnancy at the same gestational ages, and it was coupled with absolute reduction in the sodium excretion. Among preeclamptic patients, a significant inverse correlation (P less than 0.025) was revealed between the ratio and sodium excretion. Natriuresis in response to acute volume expansion with albumin infusion occurred only in 50% of preeclamptic patients, and was associated with an ANP increase, an aldosterone decrease, and a further decrease in the ratio. A blunted natriuresis was observed in cases with a particularly low prealbumin value of this ratio. Furthermore, in preeclampsia, a particularly low ratio seemed to be typical of the patients who showed poorer placental flows and fetal outcomes. These results suggest that the balance between aldosterone and ANP may be a useful index in understanding sodium homeostasis in these settings.

Extracorporeal circulation influence on plasma atrial natriuretic peptide concentration in cardiac surgery patients

An attempt was made to clarify the change of plasma human atrial natriuretic peptide (hANP) concentration before, during, and after cardiac surgery in heart failure with extracorporeal circulation. Plasma hANP concentration did not significantly decrease during total aortic cross clamping (ACC) with complete clamping of the superior and inferior vena cavae. This finding may be explained by the suppression of endopeptidase activities and the response of hANP receptors due to the low body temperature. Plasma hANP concentration strongly increased from 56.6 +/- 8.4 to 208.9 +/- 40.7 pg/ml (n = 5) by the release of total ACC. This strong increase of hANP in the plasma may occur due to the rapid increase of atrial pressure from zero to 12.5 mm Hg caused by releasing the total ACC. The molecular form of plasma hANP obtained after the release of total ACC was alpha-hANP alone, which was estimated by gel permeation chromatography and reverse HPLC.

Brain natriuretic peptide-like immunoreactivity is present in human plasma

A highly specific and sensitive radioimmunoassay (RIA) for a novel porcine brain natriuretic peptide (BNP) has been established to elucidate whether BNP-like immunoreactivity (LI) is present in human plasma. The antibody used was specific for BNP without any crossreactivities with known human atrial natriuretic peptides (hANP). After extraction of human plasma with Sep-Pak cartridge, this assay allowed for detection of BNP-LI as low as 0.1 fmol/tube. In 12 healthy subjects, the mean concentrations of plasma BNP-LI were 1.5 fmol/ml. Reverse-phase HPLC coupled with BNP RIA revealed that the single major component with BNP-LI, corresponding to porcine BNP(1 26), was apparently distinct from that of alpha-hANP. These data indicate that a small molecular mass form with BNP-LI circulates in human blood.

Diurnal change of plasma atrial natriuretic peptide concentrations in patients with congestive heart failure

Diurnal change of plasma atrial natriuretic peptide (ANP) concentration was observed in 14 patients with congestive heart failure (CHF) and in eight healthy control subjects. Blood pressure, heart rate, and plasma concentration of ANP were obtained at intervals of 4 hours beginning immediately after midnight. In the CHF group, plasma ANP concentrations at the time of blood sampling were all higher than those in the control group. Patients with severe CHF had higher plasma ANP concentrations than those in patients with less severe CHF. Plasma ANP concentration in the control group was highest at 4:00 AM and was lowest at 4:00 PM. The percent change of ANP secretion (% delta ANP): [(ANP at 4:00 AM-ANP at 4:00 PM)/ANP at 4:00 PM] x 100%, increased in the control group, while it decreased in the CHF group. Moreover, % delta ANP was much lower in patients with severe CHF than it was in patients with less severe CHF. There was a possible relation between the severity of CHF and the increase of ANP secretion associated with the relative diminution of nocturnal ANP secretion. Thus the present data imply that the diurnal change in ANP was lost in patients with CHF.

Human atrial natriuretic factor (ANF). Characterisation of a monoclonal antibody panel and its use in radioimmunoassay

The production of nine monoclonal antibodies to human atrial natriuretic factor (ANF 1-28) is described. All possible combinations of two antibodies failed to reveal any which could simultaneously bind ANF. Studies with ANF analogues and the antibodies having the three highest affinity values (KD = 5, 25 and 21 pM) indicated that the antibodies are directed to the central portion of the antigen molecule. The highest affinity antibody was able to replace polyclonal antisera in the radioimmunoassay of ANF in extracts of plasma.

Plasma human atrial natriuretic peptide levels in patients with liver cirrhosis

Plasma levels of human atrial natriuretic peptide (hANP) were investigated in patients with liver cirrhosis, and the relationships between plasma hANP levels and the following factors were studied: presence of ascites, serum and urine electrolytes, plasma renin activity, angiotensin I and II, aldosterone, catecholamines, prostaglandin derivatives, conventional liver function tests and circulating blood volume. Plasma hANP level was significantly (P less than 0.05) elevated in patients with ascites (mean = 58.6 pg/mL, s.e.m. = 8.8) compared with cases without ascites (mean = 36.6 pg/mL, s.e.m. = 2.6). With the disappearance of ascites, the level fell to normal in most cases. Urine sodium excretion was positively correlated with plasma hANP in patients without ascites, but not in patients with ascites. The plasma hANP level was disproportionately high for the rate of urinary Na excretion in cirrhotics with ascites. The plasma hANP level was not correlated with any of the other factors such as blood volume, renin-angiotensin-aldosterone levels, catecholamines and liver function tests. These results suggest that plasma hANP levels are elevated in cirrhotic patients especially with ascites, but the natriuretic response of the kidney to this raised hANP level can be impaired in patients with liver cirrhosis and ascites.

A hypothesis of the pathogenesis of preeclampsia

The Atrial Natriuretic Factor discovered by De Bold in 1981, is currently being investigated by biochemists, physiologists and cardiologists. The physiological effects of this hormone closely resemble the normal changes occurring in pregnancy. Based on the experimental data published, the rise in the concentration of Atrial Natriuretic Factor in normal pregnancies may explain the physiological changes of pregnancy. It is postulated that the failure to induce a rise in the plasma concentration of Atrial Natriuretic Factor with its protective effects against the renin-angiotensin-aldosterone system will cause preeclampsia. A prospective study to compare serial Atrial Natriuretic Factor plasma concentrations with the pregnancy outcome from the point of view of preeclampsia is proposed to test this hypothesis.

Plasma concentrations of atrial natriuretic peptide in children with persistent hypertension

Plasma concentrations of human atrial natriuretic peptide (hANP) were determined in children with persistent hypertension and in age-matched normotensive controls. We studied 40 children 6-7 years of age (Group A), and 74 children 13-14 years of age (Group B). There was no significant difference in plasma hANP concentration between hypertensives and normotensives in group A. In group B, the plasma hANP concentration in hypertensives (86.5 +/- 44.9 pg/ml: mean +/- SD) was significantly higher than in normotensives (58.8 +/- 40.4 pg/ml) (p less than 0.01). In group B, 24-hour urinary excretion of sodium and fractional excretion of sodium were not significantly different between hypertensives and normotensives. The plasma hANP correlated significantly with the fractional excretion of sodium (p less than 0.05) and the 24-hour urinary excretion of sodium (p less than 0.01) in normotensives. No such correlation was evident in the case of the hypertensives. The pathogenesis of increased plasma hANP concentration in older children with persistent hypertension remains to be investigated. In regard to the effects of hANP on renal function, hANP may contribute to the regulation of sodium handling in normotensive adolescents, whereas other regulatory mechanisms need to be considered in the case of hypertensives.

Evaluation of a direct assay for atrial natriuretic peptide

A direct radioimmunoassay for the assessment of human atrial natriuretic peptide (ANP) in plasma, using a highly specific antibody and a well-defined monoiodotyrosyl-tracer was developed and evaluated by concurrent application of an extraction method. Sensitivity was 13.4 pg/ml; intra- and interassay variations were 3.1 and 5.5%, respectively; recovery averaged 99%; normal values ranged from 15-111 pg/ml (mean +/- SD = 59 +/- 25 pg/ml, n = 41). The results, including the effect of exercise, of the two methods correlated well. Pooling ANP values in normal subjects and patients with congestive heart failure gave a good correlation (p less than 0.01). However, due to processes in unextracted plasma, in the lower range the results from the direct method were erratic. Velocity and duration of centrifugation changed the number of platelets, but no effect on ANP levels, whether assessed by the direct or by the extraction method, was observed. Although the direct method is considerably less laborious than the extracted method its lack of reliability disqualifies it for most purposes.

Quantitative analyses of atrial myoendocrine cells and plasma atrial natriuretic peptides (ANP) of the rat with special reference to the twenty-four-hour variations in secretory granules and plasma ANP concentrations

Subcellular structures of atrial myoendocrine cells in the rat heart and plasma concentrations of atrial natriuretic peptides (ANP) were examined at six evenly-spaced time points over 24 h, using morphometric techniques and radioimmunoassay. Myofibrils and mitochondria of the cells occupied 73.3% of the cytoplasm; 2% of the cytoplasm was occupied by secretory granules, rough endoplasmic reticulum and Golgi complexes, structures characteristic of endocrine cells. Plasma ANP concentration was maximal at 08.00 h, when the individual volume of secretory granules was minimal. The numerical density of secretory granules was increased at 12.00 h. The plasma ANP concentration was minimal at 20.00 h, when the numerical density was minimal and the individual volume was maximal. The fluctuation in plasma ANP concentrations over 24 h was thus parallel to that in the numerical densities of secretory granules and inverse to that in individual volumes. These results suggest that in rats the secretory activity of atrial myoendocrine cells increases at the beginning of the resting period, whereas it decreases at the beginning of the active phase.

Isolation and structural analysis of "urodilatin", a new peptide of the cardiodilatin-(ANP)-family, extracted from human urine

Two major forms of cardiac peptides have been established in the last few years: (a) a prohormone of 126 amino acids (CDD/ANP-1-126) in the endocrine heart and (b) the circulating CDD/ANP-99-126 (= alpha ANP) in blood plasma. The method we applied earlier to isolate the circulating form of cardiodilatin from human blood was used to detect and analyze the biologically active, predominant form of the same polypeptide family excreted by the kidneys. Each step of the isolation procedure was followed up by a bioassay using an in vitro vascular smooth muscle relaxation test and a highly specific RIA against cardiodilatin (CDD-99-126) for the initial purification steps. The polypeptides excreted in 1000 l of normal human urine were adsorbed to 2.5 kg of alginic acid, and after elution and lyophilization processed on a G-25 Sephadex column. The obtained crude polypeptide fractions were applied to ion-exchange chromatography. Thereafter four steps of HPLC were carried out to purify the polypeptide which was the suggested form of cardiodilatin (CDD) in human urine. The amino acid analysis and gas phase sequence analysis showed that the main form of urinary cardiodilatin is a 32 amino acid residue containing molecule, cardiodilatin-95-126. The molecule is N-terminally extended compared to the circulating CDD-99-126. This suggests that the analyzed urinary peptide is not the residual plasma form, filtrated and renally cleared from blood, but probably a polypeptide produced and processed in the kidney tubules and cleaved by a different postranslational process. Therefore, this vasorelaxant polypeptide is called urodilatin.

Atrial natriuretic peptide in human urine

A highly sensitive radioimmunoassay to measure atrial natriuretic peptide (ANP) concentration in urine has been established, and its clinical usefulness is presented. ANP in urine was stable at 4 degrees C for several days and was easily measured by our radioimmunoassay. The average ANP excretion in 65 healthy persons was 25.0 +/- 1.4 ng/day (mean +/- SEM) and the fractional excretion of ANP was 0.7 +/- 0.05%. In 14 patients with congestive heart failure, the average ANP excretion was 119.2 +/- 29.4 ng/day, which decreased to 53.3 +/- 11.0 after successful treatment.