Alpha-human Atrial Natriuretic Peptide Research Articles

OS 32-01 ATRIAL NATRIURETIC PEPTIDE IMPROVES URINE FLOW AT PROXIMAL TUBULES IN SEPTIC ACUTE KIDNEY INJURY

Objective: Carperitide, alpha-human atrial natriuretic peptide, is used in expectation of protecting the kidney during sepsis in internal care unit; however, the detailed mechanism of action has not been clarified yet. As septic acute kidney injury (AKI) does not induce characteristic histological damage, we aimed assess the effects of carperitide treatment on the decline of renal function during lipopolysaccharide-induced AKI by using real-time intravital imaging technique. Design and Method: The renal function was analyzed by the bolus-shot FITC-inulin kinetics method that visualizes the tubular flow after free filtration from glomeruli. Results: Both tubular flow and urine flow from bladder remarkably slowed down in LPS-treated rats in prior to the onset of hypotension and acidosis. The reduction of tubular flow was induced by the retention of the injected FITC-inulin at proximal tubules and, therefore, the tubular flow in the downstream nephron was markedly decreased, even at the phase in which both blood pressure and glomerular filtration were maintained. Fluid resuscitation improved the decreased tubular flow rate only in a part of nephron, displaying heterogeneity on the effect, although the urine flow rate from bladder was almost normalized. On the other hand, carperitide ubiquitously increased the tubular flow rate with normalizing urine flow from bladder. Conclusions: Carperitide improved the urine flow rate in the proximal tubules that are resistant to the fluid resuscitation in rat endotoxemic model.

Effects of Continuous Venovenous Hemofiltration on the Pharmacology of Carperitide, a Recombinant Human Atrial Natriuretic Peptide

Natriuretic peptides exert vasodilatory, natriuretic, and diuretic effects and inhibit renin and aldosterone secretion. Carperitide, a recombinant alpha-human atrial natriuretic peptide (hANP), is used for the treatment of cardiac failure. Patients with renal failure often require renal replacement therapy, and little is known about the pharmacokinetics of carperitide when used for renal replacement therapy. Eleven patients who received continuous carperitide infusion and needed continuous venovenous hemofiltration (CVVHF) for acute renal failure were observed. The plasma hANP concentration was noted and the hANP clearance during CVVHF was calculated. The results indicated that infused hANP was removed by CVVHF. Although the clearance of hANP by CVVHF was relatively lower than the expected whole body clearance, CVVHF slightly reduced plasma hANP and cyclic guanosine monophosphate concentrations and increased arterial pressure. CVVHF affects the pharmacology of infused hANP in critically ill patients. Some caution with respect to blood pressure may be necessary when carrying out CVVHF for critically ill patients receiving continuous infusion of natriuretic peptides.

Atrial Natriuretic Peptide Attenuates Ischemia/Reperfusion-Induced Renal Injury by Reducing Neutrophil Activation in Rats

Activated neutrophils have been implicated in the development of ischemia/reperfusion (I/R)-induced renal failure. Cytokine-induced neutrophil chemoattractant-1 (CINC-1), a major factor in acute inflammation, is responsible for the activation of neutrophils and for neutrophil chemotaxis to sites of injury. Atrial natriuretic peptide (ANP), a hormone synthesized by the cardiac atria, was shown to possess anti-inflammatory potential due to its potency to inhibit the production of inflammatory mediators. We examined whether the human form of ANP attenuates I/R-induced renal injury by reducing neutrophil activation in a rat model. Male Wistar rats weighing 200-240 g were observed for 24 h after reperfusion following 45-min renal ischemia. Rats were intravenously administered alpha-human ANP (alpha-hANP, 0.2 microg/kg/min) beginning immediately after ischemia and continuing for 2 h after reperfusion. CINC-1 and myeloperoxidase (MPO) concentrations were measured to assess activation of the infiltrating neutrophil. Blood urea nitrogen and serum creatinine and urinary N-acetyl beta-d-glucosaminidase (NAG) were measured as indicators of glomerular function and as a specific indicator of proximal tubular function, respectively. alpha-hANP significantly inhibited I/R-induced increases in renal CINC-1 and MPO concentrations. alpha-hANP also reduced I/R-induced increases in the concentrations of blood urea nitrogen and serum creatinine, and improved histopathologic changes, including acute tubular necrosis. These findings indicate that alpha-hANP attenuates I/R-induced acute renal injury, at least in part by reducing neutrophil activation, and may be useful in surgeries, associated with renal ischemia, as well as in renal transplantation.

Atrial Natriuretic Peptide Reduces Ischemia/Reperfusion-Induced Spinal Cord Injury in Rats by Enhancing Sensory Neuron Activation

We recently demonstrated that calcitonin gene-related peptide (CGRP) released from sensory neurons reduces spinal cord injury (SCI) by inhibiting neutrophil activation through an increase in the endothelial production of prostacyclin (PGI(2)). Carperitide, a synthetic alpha-human atrial natriuretic peptide (ANP), reduces ischemia/reperfusion (I/R)-induced tissue injury. However, its precise therapeutic mechanism(s) remains to be elucidated. In the present study, we examined whether ANP reduces I/R-induced spinal cord injury by enhancing sensory neuron activation using rats. ANP increased CGRP release and cellular cAMP levels in dorsal root ganglion neurons isolated from rats in vitro. The increase in CGRP release induced by ANP was reversed by pretreatment with capsazepine, an inhibitor of vanilloid receptor-1 activation, or with (9S, 10S, 12R)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]-benzodiazocine-10-carboxylic acid hexyl ester (KT5720), an inhibitor of protein kinase A (PKA), suggesting that ANP might increase CGRP release from sensory neurons by activating PKA through an increase in the cellular cAMP level. Spinal cord ischemia was induced in rats using a balloon catheter placed in the aorta. ANP reduced mortality and motor disturbances by inhibiting reduction of the number of motor neurons in animals subjected to SCI. ANP significantly enhanced I/R-induced increases in spinal cord tissue levels of CGRP and 6-keto-prostaglandin F(1alpha). a stable metabolite of PGI(2). ANP inhibited I/R-induced increases in spinal cord tissue levels of tumor necrosis factor and myeloperoxidase. Pretreatment with 4'-chloro-3-methoxycinnamanilide (SB366791), a specific vanilloid receptor-1 antagonist, and indomethacin reversed the effects of ANP. These results strongly suggest that ANP might reduce I/R-induced SCI in rats by inhibiting neutrophil activation through enhancement of sensory neuron activation.

Efficacy of Low-Dose Continuous Infusion of .ALPHA.-Human Atrial Natriuretic Peptide (hANP) During Cardiac Surgery Possibility of Postoperative Left Ventricular Remodeling Effect

The aim of the present study was to evaluate the efficacy of alpha-human atrial natriuretic peptide (hANP) in cardiac surgery under cardiopulmonary bypass (CPB). A prospective randomized study was conducted with 150 patients who underwent scheduled coronary artery bypass grafting to compare a group of patients receiving 0.02 microg x kg(-1) x min(-1) of hANP from the initiation of CPB with a group not receiving hANP. Hemodynamics, levels of atrial and brain natriuretic peptides (BNP), angiotensin-II and aldosterone, renin activity, and left ventricular (LV) function were examined. The hANP group showed significantly lower renin activity and lower levels of angiotensin-II and aldosterone during the early postoperative period, compared with the non-hANP group. The incidence of postoperative ventricular arrhythmia and the postoperative peak level of creatine kinase-MB were significantly lower in the hANP group. BNP at 1 month after surgery and measures of LV function were also significantly lower in the hANP group. Low-dose continuous infusion of hANP during cardiac surgery not only had a compensatory effect for the imperfections of CPB during the early postoperative period but also an inhibitory effect on postoperative LV remodeling and a reduction in ischemia/reperfusion injury. hANP should be part of the postoperative care for cardiac surgery.

The Influence of Diastolic Function on Angiotensin Receptor Blockade in Patients with Mild Left Ventricular Dysfunction

Purpose: The aim of this study was to examine the influence of diastolic function on angiotensin II type I receptor blocker (ARB) in patients with mild left ventricular (LV) dysfunction already treated with angiotensin converting enzyme (ACE) inhibitors. Method: Diastolic function and neurohumoral variables were evaluated in 15 patients with mild LV dysfunction already treated with ACE inhibitors before and 4 weeks after administration of the ARB, telmisartan 40 mg. Diastolic function was determined by Doppler derivatives of mitral inflow (E/A ratio, deceleration time of early inflow) and pulmonary venous flow velocity (S/D ratio). B-natriuretic peptide (BNP), alpha-human atrial natriuretic peptide (HANP), plasma renin and plasma aldosteron were measured. Result: Arterial blood pressure decreased significantly after telmisartan (p 0.01). MV-E/A, deceleration time and isovolmic relaxation time did not changed after telmisartan. But pulmonary venous flow velocity improved significantly from 43 4 from 37 3 after telmisartan (p 0.05). Moreover, BNP decreased significantly from 143 85 to 76 47 pg/mL after telmisartan (p 0.05). Plasma renin, plasma aldosteron and HANP did not change after telmisartan. Conclusion: ARB telmisartan improves diastolic dysfunction in patients with mild LV dysfunction already treated with ACE inhibitors.

Multicenter Prospective Investigation on Efficacy and Safety of Carperitide for Acute Heart Failure in the 'Real World' of Therapy

Efficacy and safety assessments for carperitide (alpha-human atrial natriuretic peptide) in previous clinical trials have not mentioned its limitations in practice as therapy for acute heart failure. A 6-year prospective open-label registry analysis was conducted in the 'real world' of therapy for 3,777 patients with acute heart failure (male 57%, median age 73) treated with 0.085 microg . kg(-1) . min(-1) (median, interquartile 0.05-0.1) of carperitide for 65 h (median, interquartile 22-142); 51% were assessed as class III or IV according to the Killip classification; 82% of the patients were assessed as clinically improved after carperitide treatment. The efficacy limitation was related to the underlying disease (acute myocardial infarction), severity of Killip classification (Class IV), and renal function disturbance. The efficacy was significantly higher in patients with decompensated chronic heart failure (ie, cardiomyopathy, valvular diseases, and hypertensive heart disease). Incidence of adverse events was 16.9%, the most frequent being blood pressure lowering (9.5%), which occurred in the first 3 h of infusion, with 96% of patients recovering or improving without specific treatment. Logistic regression analysis revealed that factors predicting mortality (11.4%) during 7 days of follow-up were age, Killip classification, renal function disturbance, low blood pressure and use of vasopressors. The clinical condition improved in 82% of patients treated with carperitide. Based on these findings, minute strategy will be established for carperitide therapy within the strata of patient characteristics that may predict the prognosis.

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.

Preischemic infusion of alpha-human atrial natriuretic peptide elicits myoprotective effects against ischemia reperfusion in isolated rat hearts.

Carperitide, a synthetic alpha-human atrial natriuretic peptide (ANP) is a newly developed drug for the treatment of heart failure. However, effects of carperitide on susceptibility to ischemia reperfusion injury are left to be determined. Isolated rat hearts were subjected to Langendorff perfusion. Six hearts received 0.1 microM of carperitide for 10 min, 6 hearts received 1 mM of a NO synthetase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) for 5 min before the infusion of carperitide, 6 hearts received 0.02 microM of a PKC synthetase inhibitor chelerythrine chloride for 5 min before the infusion of carperitide, 6 hearts received 100 microM of a selective mitochondrial ATP-sensitive potassium (KATP) channel blocker 5-dehydroxydecanoate (5HD) before the infusion of carperitide, 6 hearts received 10 microM of a soluble guanylate cyclase inhibitor methylene blue for 5 min before the infusion of carperitide, and 6 hearts served as a control with no drug infusion. All hearts were then subjected to 20 min of global ischemia followed by 120 min of reperfusion. Left ventricular pressures and coronary flow were measured throughout the experiment and infarct size was detected at the end of experiment. Both plasma and tissue cGMP levels were also determined. The results showed: (1) Carperitide significantly reduced infarct size compared to control (26.1 +/- 2.8 vs. 42.7 +/- 2.3%, carperitide vs. control, p < 0.05). This effect was reversed by L-NAME, chelerythrine and 5HD, but not methylene blue. (2) Plasma cGMP levels were increased in carperitide-treated group. This effect was reversed by L-NAME (0.16 +/- 0.03 vs. 1.04 +/- 0.09* vs. 0.28 +/- 0.02 nmol/L, control vs. carperitide vs. L-NAME, *p < 0.01 vs. control). We conclude that preischemic infusion of carperitide exerts cardioprotective effects possibly through NO-PKC dependent pathway followed by mitochondrial KATP channel activation.

Properties and modulation of alpha human atrial natriuretic peptide (α-hANP)-formed ion channels

Using the lipid bilayer technique we have optimized recording conditions and confirmed that alpha human atrial natriuretic peptide [alpha-hANP(1-28)] forms single ion channels. The single channel currents recorded in 250/50 mM KCl cis/trans chambers show that the ANP-formed channels were heterogeneous, and differed in their conductance, kinetic, and pharmacological properties. The ANP-formed single channels were grouped as: (i) H202- and Ba2+-sensitive channel with fast kinetics; the nonlinear current-voltage (I-V) relationship of this channel had a reversal potential (Erev) of -28.2 mV, which is close to the equilibrium potential for K+ (EK = -35 mV) and a maximal slope conductance (gmax) of 68 pS at positive potentials. Sequential ionic substitution (KCl, K gluconate and choline Cl) of the cis solution suggests that the current was carried by cations. The fast channel had three modes (spike mode, burst mode, and open mode) that differed in their kinetics but not in their conductance properties. (ii) A large conductance channel possessing several subconductance levels that showed time-dependent inactivation at positive and negative membrane potentials (Vm). The inactivation ratio of the current at the end of the voltage step (Iss) to the initial current (Ii) activated immediately after the voltage step, (Iss/Ii), was voltage dependent and described by a bell-shaped curve. The maximal current-voltage (I-V) relationship of this channel, which had an Erev of +17.2 mV, was nonlinear and the value of gmax was 273 pS at negative voltages. (iii) A transiently-activated channel: the nonlinear I-V relationship of this channel had an Erev of -29.8 mV and the value of gmax was 160 pS at positive voltages. We propose that the voltage-dependence of the ionic currents and the kinetic parameters of these channel types indicate that if they were formed in vivo and activated by cytosolic factors they could change the membrane potential and the electrolyte homeostasis of the cell.

The effects of alpha-human atrial natriuretic peptide and milrinone on pial vessels during blood-brain barrier disruption in rabbits.

The effects of alpha-human atrial natriuretic peptide (HANP) and milrinone on cerebral pial vessels, especially during blood-brain barrier (BBB) disruption, are not clear. We studied topical HANP (10(-14), 10(-12), and 10(-10) M) or milrinone (10(-7), 10(-5), and 10(-3) M), and IV HANP (0.1, 0.2, and 1.0 microg. kg(-1). min(-1)) or milrinone (0.5, 5.0, and 20.0 microg. kg(-1). min(-1)) with or without hyperosmolar BBB disruption, using a rabbit cranial window preparation. At 10(-12) and 10(-10) M topical HANP produced significant arteriolar (16%, 20%, respectively), but no venular dilation. Topical milrinone (10(-3) M) produced significant arteriolar and venular dilation (21%, 8%, respectively). IV HANP produced no arteriolar or venular changes at any dose except during BBB disruption, when it caused a significant arteriolar (16%, 16%, and 17%, respectively), but no venular dilation. In contrast, IV milrinone caused small but significant arteriolar and venular dilation without BBB disruption (arterioles, 6%, 7% and 8%, respectively; venules, 6% at 20.0 microg. kg(-1). min(-1)). During BBB disruption, these responses to milrinone were similar. Although HANP and milrinone each have a direct vasodilator effect on arterioles, their systemic administration at clinical doses could induce different effects. BBB disruptive conditions could increase the response of pial vessels to systemically administered HANP. Although alpha-human atrial natriuretic peptide (HANP) and milrinone each have a direct vasodilator effect on cerebral pial arterioles, their systemic administration at clinical doses could have different effects and blood-brain-barrier disruptive conditions could alter the response of pial vessels to HANP, but not to milrinone.

Plasma concentration and urinary excretion of N-terminal proatrial natriuretic peptides in patients with kidney diseases

Biologically active N-terminal fragments such as proANP(1-30), proANP(31-67), and proANP(1-98) derive from the prohormone of alpha-human atrial natriuretic peptide [proANP(99-126) or alpha-ANP]. No systematic data are available for patients with different kidney diseases. Specific immunoassays were developed to determine plasma and urine concentrations of these fragments in 121 patients with different degrees of kidney function and urinary protein excretion, respectively. In patients with kidney disease and normal renal function without proteinuria, circulating proANP(1-30) and proANP(31-67) increased 2.8-fold and 6.5-fold, respectively. Urinary excretion of proANP(31-67) increased by a factor of 7.7 in these patients, whereas proANP(1-30) was not affected. Patients with impaired renal function had a dramatic increase of urinary proANP(31-67) excretion even before serum creatinine levels started to rise. The progression of renal failure caused a significant rise of circulating proANP(1-30) (4.3-fold) and proANP(31-67) (3.0-fold) compared with patients with normal renal function. Urinary excretion of proANP peptides significantly increased, particularly when the serum creatinine level was> 5.0 mg/dL [proANP(1-30) 26-fold, proANP(31-67) 8.4-fold]. Urinary excretion of proANP(1-30) increased up to 4.4-fold and urinary excretion of proANP(31-67) increased up to 2.4-fold in patients with proteinuria in excess of 3 g/24 h. Plasma concentrations and urinary excretion of proANP(1-30) and proANP(31-67) are affected by kidney disease and function, but not by proteinuria per se. It is proposed that the diseased kidney increases early urinary excretion of proANP fragments to participate in the regulation of renal function as well as sodium and water excretion.

Alpha-human atrial natriuretic peptide, carperitide, reduces infarct size but not arrhythmias after coronary occlusion/reperfusion in dogs.

Carperitide, a recombinant form of alpha-hANP, possesses potent diuretic, natriuretic, and vasodilatory activity, and inhibits the renin-aldosterone system and sympathetic nervous activity. However, its beneficial effects on ischemic myocardium have not been studied fully. We examined carperitide's effects on infarct size, hemodynamics, and arrhythmia frequency in anesthetized dogs (n = 20) subjected to a 90-min coronary artery occlusion/6-h reperfusion protocol. Intravenous infusion of carperitide (0.2 microg/kg/min) commenced 15 min after occlusion and continued during occlusion/reperfusion. Ventricular fibrillation developed in two of 10 control versus three of 10 treated dogs (p = NS). Hemodynamics, collateral blood flow to the ischemic wall measured 10 min after occlusion, and extent of area at risk were comparable for the two groups. Infarct size/area at risk was smaller in treated than in control dogs (4.5 +/- 2.1% vs. 27.8 +/- 7.8%, respectively; p < 0.05). During occlusion, carperitide tended to increase collateral blood flow (+39%) and significantly decreased left ventricular systolic pressure (-13%) and end-diastolic pressure (-40%) compared with baseline. In control dogs, collateral blood flow tended to decrease (-8.3%), whereas most hemodynamic parameters did not change significantly with respect to baseline. The number of arrhythmias recorded during occlusion/reperfusion was similar in the two groups. Intravenous administration of carperitide limited infarct size, but did not reduce incidence of ventricular arrhythmias after 90-min coronary occlusion/6-h reperfusion in anesthetized dogs. Although the beneficial effects of carperitide may be attributable to concomitant changes in hemodynamics and collateral blood flow, the precise mechanisms require further investigation.

N-terminal fragments of the proatrial natriuretic peptide in patients before and after hemodialysis treatment

Fragments derived from the prohormone of alpha-human atrial natriuretic peptide (alpha-ANP) in patients with cardiac failure are more closely related to the disease state than intact alpha-ANP. Specific immunoassays have been developed to detect proANP 1-30, proANP 31-67, and proANP 1-98. Plasma concentrations of these fragments were determined in 122 hemodialysis patients with and without cardiac dysfunction, with and without hypertension, as well as with and without dialysis-associated hypotensive episodes either before or after a regularly scheduled hemodialysis session. The effects of different dialyzer membranes were also evaluated. The results of these assays along with other markers of volume regulation such as alpha-ANP and cyclic 3',5' guanosine monophosphate (cGMP) were compared with those of healthy controls. Predialytic and postdialytic plasma concentrations of the proANP fragments were markedly higher in uremic patients than in controls (98-fold for proANP 1-98, 56-fold for proANP 31-67, and 35-fold for proANP 1-30). All proANP fragments, alpha-ANP, and cGMP decreased during hemodialysis. A strong linear correlation was found between predialytic and postdialytic plasma levels. There was no correlation, however, with the amount of fluid removed during hemodialysis. Patients with altered left ventricular hemodynamics displayed significantly higher plasma concentrations of all proANP fragments and alpha-ANP, but not cGMP, than patients with normal cardiac function. Hemodialysis patients with moderate or severe hypertension had higher concentrations of proANP fragments, alpha-ANP, and cGMP than patients with normal blood pressure or patients with only mild hypertension. There was no significant difference in circulating levels of proANP peptides, alpha-ANP, and cGMP between patients with and without frequent dialysis-associated hypotensive episodes. Cellulose-triacetate dialyzers reduced plasma levels of proANP 1-30, proANP 31-67, and proANP 1-98 significantly more than polysulfone dialyzers, but alpha-ANP and cGMP levels were not different. Circulating alpha-ANP and proANP fragments are influenced by a variety of factors such as end-stage renal disease, hemodialysis treatment, dialyzer membrane material, cardiac dysfunction, and hypertension. Therefore, these are not useful markers to accurately estimate volume status in hemodialysis patients.

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.

Beneficial Effect of Atrial Natriuretic Peptide on Pulmonary Gas Exchange in Patients With Acute Lung Injury

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. Prospective, randomized, comparable study. ICU of a university hospital. Forty patients with moderate acute lung injury (lung injury score > or = 2.0) who required mechanical ventilation with PEEP were studied. 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. 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. The results suggest that ANP infusion induces diuresis and improves pulmonary gas exchange in patients with acute lung injury during mechanical ventilation with PEEP.

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.

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

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

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.

Purification of an L‐asparaginase—atrial natriuretic peptide fusion protein expressed in Escherichia coli

A novel fusion protein designed to facilitate protein purification was expressed in Escherichia coli and purified separately by two different chromatography methods. L-Asparaginase from Erwinia chrysanthemi is fused to the N-terminus of a model peptide, alpha-human atrial natriuretic peptide (alpha-hANP). L-Asparaginase was chosen because of its selective affinity for L-asparagine and because of its unusually high isoelectric point(8.6). A gene construction without the L-asparaginase native signal sequence caused expression at a level of 8% of total cell protein, while gene construction with the native signal sequence resulted in over five time less expression. The hybrid protein expressed without the signal sequence was purified from clarified cell lysate byeither L-asparagine affinity chromatography or cation exchange chromatography. After digestion of the fusion protein with factor Xa protease, a peptide with a molecular weight corresponding to the theoretical molecular weight of alpha-hANP was observed by coupled HPLC/mass spectrometry. (c) 1995 John Wiley & Sons Inc.