Natriuretic peptides and acute renal failure.

Atrial natriuretic peptides (ANPs) are a family of peptide hormones, e.g., ANP, long-acting natriuretic peptide, vessel dilator, and kaliuretic peptide synthesized by the ANP gene. Brain natriuretic peptide (BNP) and C-type natriuretic peptide are also members of this family but are synthesized by separate genes. Within the kidney, the ANP prohormone's posttranslational processing is different from that of other tissues, resulting in an additional four amino acids added to the NH2 terminus of ANP (e.g., urodilatin). Each of these natriuretic and diuretic peptides increases within the circulation with acute renal failure (ARF). Renal transplantation but not hemodialysis returns their circulating concentrations to those of healthy individuals. BNP and adrenomedullin, a 52-amino acid natriuretic peptide, have beneficial effects on glomerular hypertrophy and glomerular injury but do not improve tubular injury (i.e., acute tubular necrosis). Vessel dilator ameliorates acute tubular necrosis with regeneration of the brush borders of proximal tubules. Vessel dilator decreases mortality in ARF from 88 to 14% at day 6 of ARF, even when given 2 days after renal failure has been established.

Related papers:

title: The effects of low dose intravenous 99-126 atrial natriuretic factor infusion in patients with chronic renal failure.
abstract: The aim was to study the renal and hormonal effects of intravenous 99-126 atrial natriuretic factor (ANF) infusion in a mixed group of patients who had moderate to severe chronic renal failure (CRF) and who were not treated with dialysis. The peak mean plasma level of ANF achieved during the experiment was at the upper limit of an absolute range of basal values previously recorded in a larger group of patients with similar degrees of renal impairment. A significant tissue effect was confirmed by rises in plasma and urinary cyclic guanosine monophosphate, the 'second-messenger' of ANF. ANF infusion increased sodium excretion rate by a mean of 68% compared with a fall of 40% in a placebo group, and significant increases in urinary albumin excretion occurred during the peptide infusion. Thus, the high levels of plasma ANF found in CRF may have a role in the maintenance of sodium balance. In addition, the proteinuric effect may be detrimental to long-term renal function.

title: Hospital-acquired renal insufficiency: a prospective study.
abstract: Twenty-two hundred sixty-two consecutive medical and surgical admissions were evaluated prospectively to determine the contribution of iatrogenic factors to the development of renal insufficiency in hospital. Of 2,216 patients at risk, some degree of renal insufficiency developed in 4.9 percent. Decreased renal perfusion, postoperative renal insufficiency, radiographic contrast media, and aminoglycosides accounted for 79 percent of the episodes. Iatrogenic factors, broadly defined, accounted for 55 percent of all episodes. Poor prognostic indicators included oliguria, urine sediment abnormalities and, most importantly, severity of renal insufficiency; with an increase in serum creatinine of 3 mg/dl or greater, the mortality rate was 64 percent. Age, admission serum creatinine levels, and the number of episodes of renal insufficiency did not significantly affect outcome. We conclude that there is a substantial risk of the development of renal failure in hospital and that the mortality rate due to hospital-acquired renal insufficiency remains high.

title: Prevention of drug-induced nephrotoxicity in the intensive care unit.
abstract: Acute renal failure (ARF) occurs in 5% to 25% of all admissions to an intensive care unit (ICU). The development of ICU-associated ARF increases the average mortality from about 15% to more than 60%. ARF is also associated with significant prolongation of hospital stay as well as substantial expense. Recent studies suggest that a significant percent of hospital-acquired ARF is caused by nephrotoxins. This brief review will discuss the frequency of occurrence, pathophysiology, risk factors, clinical course, and prevention of nephrotoxicity that may occur after exposure to aminoglycosides, nonsteroidal anti-inflammatory drugs, and radiographic contrast agents.

title: Norepinephrine-induced acute renal failure: beneficial effects of atrial natriuretic factor.
abstract: The effect of the atrial natriuretic factor (ANF) on early norepinephrine-induced acute renal failure (ARF) was investigated. In anaesthetized female Sprague-Dawley rats, weighing 247 +/- 36 g, ARF of the left kidneys was induced by 40-min intrarenal arterial infusion of norepinephrine (NE; 0.75 micrograms/kg body weight). In each case the right kidney served as a control organ. Inulin clearance was used as an estimate of glomerular filtration rate (GFR). Urine volume (V), GFR and fractional excretion rates of sodium, potassium and chloride were studies in both kidneys. Immediately after NE-induced ARF one group received ANF (alpha-hANaP) and the other groups 5% glucose or isotonic saline; all infusions were administered intrarenally. In the experimental kidney NE-infusion induced anuria. ANF infusion was able to induce complete reversal of the NE effect, and GFR and diuresis improved markedly in the experimental kidney. In addition, a tremendous rise in fractional excretion rates of sodium and potassium after administration of ANF was observed. In the control kidney an additional increase of GFR and diuresis was seen. Following 5% glucose or isotonic sodium chloride infusion, no profound effects were obtained in both kidneys. The results of the present study demonstrate that ANF provides beneficial effects on the functional damage of NE-induced ARF. We conclude that the NE-antagonistic effect of ANF and the consecutive amelioration of GFR may play an important role in the recovery of impaired renal function.

title: MOLECULAR BIOLOGY AND BIOCHEMISTRY OF NATRIURETIC PEPTIDE FAMILY
abstract: The natriuretic peptide family consists of three endogenous ligands; atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C‐type natriuretic peptide (CNP), and is involved in the regulation of cardiovascular homeostasis. Both ANP and BNP act mainly as cardiac hormones and are produced predominantly by the atrium and ventricle, respectively. Expression of the BNP and ANP genes is greatly augmented in patients with congestive heart failure and animal models of ventricular hypertrophy or cardiomyopathy. In the heart, the BNP gene expression is regulated differently from the ANP gene expression both at transcriptional and post‐transcriptional levels. Transgenic technology has provided the direct evidence that BNP as well as ANP is involved in the chronic blood pressure control. Contrasting with ANP and BNP, CNP does not act as a cardiac hormone but as a neuropeptide or an endothelium‐derived autocrine/paracrine regulator. Endothelial production of CNP is remarkably augmented by various cytokines and growth factors such as transforming growth factor‐β and tumour necrosis factor‐α, suggesting the pathophysiological significance of CNP in the process of various vascular disorders. Chromosomal mapping of natriuretic peptides has revealed that the CNP gene is localized on mouse chromosome 1, while ANP and BNP are tightly linked on mouse chromosome 4, suggesting that CNP, a local regulator, is functionally and evolutionarily distinct from ANP and BNP, both of which are cardiac hormones. Understanding the molecular biology and biochemistry of the natriuretic peptide family will lead to the better understanding of its physiological and pathophysiological implication, and the clinical application in cardiorenal regulation.

title: Atrial natriuretic factor and related peptide hormones.
abstract: I. PERSPECTIVES AND SUMMARY 230 II. CLASSIFICATION OF CARDIAC PEPTIDE HORMONES """"""""""" " "" 231 Type A Natriuretic Peptides . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 Type B Natriuretic Peptides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 Type C Natriuretic Peptides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 III. MOLECULAR BIOLOGY OF ANF GENE EXPRESSION 235 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 Factors that Regulate ANF Gene Transcription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 Cis-Acting Sequences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 Cardiac Trans-Acting Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 IV. PEPTIDE PROCESSING AND RELEASE... ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 ANF Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 ANF Rele·ase.. . . . . . . . . . .. . .. . . . . . . . . . . . . . . . . . ........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 V. BIOCHEMISTRY OF PHARMACOLOGIC ACTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 ANF Receptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 Physiologic Effects of ANF """"""""""""""""""""""""""""""""" ' "

title: Atrial Natriuretic Peptide Prohormone Gene Expression: Hormones and Diseases That Upregulate its Expression
abstract: Atrial natriuretic peptides consist of a family of peptide hormones that are synthesized by three separate genes and then stored as three different prohormones (i.e., 126‐amino acid [a.a.]) atrial natriuretic peptide (ANP), 108‐a.a. brain natriuretic peptide (BNP), and 126‐a.a. C‐natriuretic peptide (CNP) prohormones. The gene encoding for the synthesis of the atrial natriuretic peptide prohormone (proANP) consists of three exons and two introns. Exon 1 encodes the signal peptide and the first 16 a.a. of the ANP prohormone. These 16 a.a. form the N ‐terminus of a peptide hormone named long‐acting natriuretic hormone (LANH). A valine‐to‐methionine substitution in LANH results in a 2‐fold increased incidence of strokes in humans. Exon 2 of the proANP gene encodes for three peptide hormones, i.e., vessel dilator, kaliuretic hormone, and ANP. Each of the proANP gene products have vasodilatory, diuretic, natriuretic, and/or kaliuretic properties. Stretch, glucocorticoids, thyroid hormone(s), mineralocorticoids, and calcium enhance proANP gene expression. Enhanced proANP gene expression is found in congestive heart failure, hypertension, and cirrhosis with ascites. The proANP gene is present with invertebrates and plants as well as in humans and other vertebrates.

title: C-Type Natriuretic Peptide
abstract: C-type natriuretic peptide is a 22-amino acid peptide that was initially identified in the central nervous system. The distribution of C-type natriuretic peptide, which has structural homology with atrial and brain natriuretic peptides, is wide and includes the endothelium, myocardium, gastrointestinal, and genitourinary tracts. The biological effects of this peptide are being elucidated in a number of sites in a number of species; however, the novel endothelial site of production of C-type natriuretic peptide and the proximal situation of its receptor in vascular smooth muscle suggest that this vascular natriuretic peptide system may play a role in concert with other local systems in the control of vascular tone.

title: Natriuretic peptides and the kidney: current concepts.
abstract: The field of study of natriuretic peptides becomes more complex as we enter the second decade since their discovery. The attractive hypothesis that a single peptide secreted by the atria could regulate the physiological responses to salt and water loading has proven simplistic. Rather the atrial natriuretic peptide story has opened the door on a whole family of peptides, secreted from the atria, the ventricles, the brain, and even the kidney itself, all working in concert to achieve this regulation. The regulation of renal function by natriuretic peptides is presumably the result of the integration of these different peptides effects. Thus while atrial derived NP circulates and has direct effects on the glomerulus, other sources of NP (such as the kidney) may be responsible for some of the tubular effects of NP. Further definition of the mechanisms of regulation of the kidney derived NP are needed before any further conclusions can be drawn.

title: Adrenomedullin: potential in physiology and pathophysiology.
abstract: Adrenomedullin (ADM), a 52-amino acid ringed-structure peptide with C-terminal amidation, was originally isolated from human pheochromocytoma. ADM mediates vasodilatory and natriuretic properties through the second messenger cyclic adenosine 3',5'-monophosphate (cAMP), nitric oxide and the renal prostaglandin system. ADM immunoreactivity and its gene are widely distributed in cardiovascular, pulmonary, renal, gastrointestinal, cerebral and endocrine tissues. ADM is also synthesized and secreted from vascular endothelial and smooth muscle cells. When injected intravenously, ADM increases flow rates predominantly in organs in which the ADM gene is highly expressed, suggesting that ADM acts as a local autocrine and/or paracrine vasoactive hormone. In addition, ADM is a circulating hormone and its plasma concentration is increased in various cardiorenal diseases such as hypertension, chronic renal failure and congestive heart failure. Current evidence suggests that ADM plays an important role in fluid and electrolyte homeostasis and cardiorenal regulation, however further investigations are required to address the importance of ADM under various physiological and pathophysiological conditions.

title: BRAIN NATRIURETIC PEPTIDE IN HEART FAILURE
abstract: cause tissue damage by local deposition of toxic eosinophil proteins. The combination of long-term corticosteroid inhaler use, frequent asthmatic attacks (with increased air trapping and pressure), and the detrimental effect of eosinophils on tissues may lead to the development of laryngocele and laryngopyocele, as seen in this particular patient. Observational and case series studies are needed to further define the association among these factors.

title: Adrenomedullin and the control of fluid and electrolyte homeostasis.
abstract: Two potent hypotensive peptides, adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP), are encoded by the adrenomedullin gene. AM stimulates nitric oxide production by endothelial cells, whereas PAMP acts presynaptically to inhibit adrenergic nerves that innervate blood vessels. Complementary, but mechanistically unique, actions also occur in the anterior pituitary gland where both peptides inhibit adrenocorticotropin release. In the adrenal gland both AM and PAMP inhibit potassium and angiotensin II-stimulated aldosterone secretion. Natriuretic and diuretic actions of AM reflect unique actions of the peptide on renal blood flow and tubular function. In the brain AM inhibits water intake and, in a physiologically relevant manner, salt appetite. Both AM and PAMP act in the brain to elevate sympathetic tone, effects that mirror the positive inotropic action of AM in the heart. Cardioprotective actions in the brain and heart may be important counter-regulatory actions that buffer the extreme hypotensive actions of the peptides when released in sepsis. Thus the biologic actions of the proadrenomedullin-derived peptides seem well coordinated to contribute to the physiologic regulation of volume and electrolyte homeostasis.

title: Atrial natriuretic peptides in pathophysiological diseases.
abstract: Time for primary review 32 days. 

Atrial natriuretic peptides (ANPs) consist of a family of peptides which are synthesized and then stored as three different prohormones (i.e., 126 amino acid [a.a.] atrial natriuretic peptide (ANP), 108 a.a. brain natriuretic peptide (BNP), and 126 a.a. C-natriuretic peptide prohormones (CNP) prohormones) . The present review will concentrate on atrial peptides and especially on the natriuretic peptides originating from the ANP prohormone in pathophysiological conditions. There are several excellent recent reviews on the biochemistry and molecular biology of the natriuretic peptides [2,3] and their physiology [4–6] so these aspects will not be reviewed in detail in the present review.

 molecular biology of natriuretic peptides

To understand which of the atrial natriuretic peptides may be associated with cerebrovascular accidents (i.e., strokes) [7,8] and other cardiovascular disease states, it is necessary to briefly review the molecular biology of how the respective atrial natriuretic peptides are synthesized. The gene encoding for the synthesis of atrial natriuretic peptide preprohormone consists of three exons (coding) sequences separated by two intron (intervening) sequences  [9–12]. Exon 1 encodes the signal peptide which is cleaved from the preprohormone (152 a.a.) in the endoplasmic reticulum to form a prohormone of 126 a.a., which is the storage form of the various atrial peptide hormones within tissues [11–13]. Exon 1 also encodes for the first 16 amino acids of this prohormone [9–12] which after proteolytic processing of the ANP prohormone is also the first 16 a.a. of a peptide hormone named long acting natriuretic peptide (LANP) . Exon 3 encodes for the terminal tyrosine (i.e., a.a. 126 of the ANP prohormone) in humans and 3 a.a. (Try-Arg-Arg) in rat, mouse, rabbit, and cow [9–13]. Exon 2 encodes for the rest of the prohormone (i.e., a.a. 17–125 in humans) [9–13].



Fig. 1 
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* Tel.: +1-813-972-7624; fax: +1-813-972-7623 vesely.david_l{at}tampa.va.gov

title: Effect of proANF-(31--67) on sodium excretion in conscious monkeys.
abstract: The purpose of this study was to determine the effect of proANF-(31--67) on renal function in conscious, chronically instrumented monkeys (Macaca fascicularis). The experimental protocol consisted of a 30-min control period followed by 60 min of peptide infusion and a 30-min recovery period. Atrial natriuretic factor (ANF)-(99--126), proANF-(31--67), of a combination of ANF-(99--126) plus proANF-(31--67) was infused at 15 pmol.kg-1.min-1. ANF-(99--126) caused sodium excretion to increase from 12.5 +/- 3 to a peak of 37.9 +/- 10.4 mueq/min, whereas fractional sodium excretion (FENa) increased from 0.69 +/- 0.2 to 2.3 +/- 0.43%. ProANF-(31--67) increased sodium excretion from 12.7 +/- 5 to a peak of 23.3 +/- 9.0 mueq/min and FENa from 0.56 +/- 0.07 to a peak of 1.15 +/- 0.4%. When ANF-(99--126) and proANF-(31--67) were infused in combination, sodium excretion increased from 9.6 +/- 3 to a peak of 5.19 +/- 12.5 mueq/min, whereas FENa increased from 0.97 +/- 0.4 to 3.9 +/- 1.1%. Mean arterial pressure decreased by approximately 10 mmHg in all three groups. These findings indicate that intravenously administered proANF-(31--67) causes an increase in sodium excretion and that when proANF-(31--67) and ANF-(99--126) are given in combination, they act in an additive fashion to increase renal sodium excretion.

title: ATRIAL NATRIURETIC PEPTIDE FRAGMENTS IN DOGS WITH EXPERIMENTAL HEART FAILURE
abstract: 1. This study in the canine arteriovenous (AV) fistula model of high‐output heart failure (HOHF) evaluated the chronic temporal changes in plasma ANF and pro ANF 31–67 and their relationship to body‐fluid balance and the renin‐aldosterone axis. In addition, the haemodynamic, hormonal and renal excretory effects of synthetic pro ANF 31–67 infusions were examined in normal and AV fistula dogs with compensated HOHF.

title: Three peptides from the ANF prohormone NH(2)-terminus are natriuretic and/or kaliuretic.
abstract: The present investigation was designed to determine whether peptides derived from the NH(2)-terminal portion of the 126-amino acid prohormone (pro) of atrial natriuretic factor (ANF) have natriuretic and diuretic properties similar to ANF. Three peptides consisting of amino acids 1-30 [(proANF-(1-30)], 31-67 [proANF-(31-67)], and 79-98 (proANF-(79-98)] of the ANF prohormone were tested and compared with the COOH-terminus peptide (ANF) with respect to their ability to increase urine volume, urine sodium and potassium excretion, and glomerular filtration rate (GFR) in anesthetized Munich-Wistar rats. Each of these peptides except proANF-(79-98) caused a significant diuresis (P less than 0.05) when infused at their respective 100 ng.kg body wt-1.min-1 concentrations for 120 min. ProANFs-(1-30), (31-67), (79-98), and (99-126) (ANF) increased sodium excretion by 231, 973, 167, and 1,405%, respectively. The fractional excretion of sodium compared with control was significant at P less than 0.05, P less than 0.01, and P less than 0.05 for proANFs (1-30), (31-67), and (99-126), respectively. ProANF-(79-98) did not significantly increase the fractional excretion of sodium, but it was the only peptide from the NH(2)-terminus of the prohormone that significantly increased the fractional excretion of potassium's ProANF-(31-67) did not increase urinary potassium excretion. ProANF-(1-30), (79-98), and ANF significantly (P less than 0.05) increased urinary potassium excretion. None of these peptides significantly enhanced GFR. In conclusion, three peptides from the NH(2)-terminus of the ANF prohormone as well as ANF (the COOH-terminus) have either natriuretic, kaliuretic, and/or diuretic properties, but the respective ability of each of these peptides to produce these effects varies considerably.

title: Atrial natriuretic prohormone peptides 1-30, 31-67, and 79-98 vasodilate the aorta.
abstract: Human prohormone atrial natriuretic peptides 1-30, 31-67, and 79-98 caused vasodilation of porcine aortas which began in 30 seconds and was maximal at 10 minutes. These three peptides were found to be equally potent to atrial natriuretic factor in their vasodilatory activity which was found with or without endothelium present. This vasodilation was associated with a 4 to 5 fold increase in cyclic GMP in the aorta secondary to activation of particulate guanylate cyclase [E.C. 4.6.12]. These data demonstrate that three N-terminal peptide segments of the atrial natriuretic factor prohormone cause vasodilation.

title: Hemodynamic and renal effects of ProANF31-67 in hypertensive rats.
abstract: It has been demonstrated previously that the atrial natriuretic factor prohormone fragment 31-67 (ProANF31-67) circulates in animals and possesses natriuretic and vasodilating actions. Although the plasma levels of the peptide are reportedly elevated in patients with high blood pressure, its role and actions in hypertension are unknown. In the present study, synthetic human ProANF31-67 was infused intravenously at doses of 0, 10, 30, and 100 ng/kg/min into respective groups of anesthetized normotensive and spontaneously hypertensive rats. Mean arterial pressure (MAP), urine flow rate (UV), and sodium excretion (UNaV) were measured during two consecutive 30-min periods. In both strains of rats, reductions in MAP with ProANF31-67 were similar in magnitude and dose-related. Sodium excretion responses to the peptide infusions also were remarkably similar in both normotensive and hypertensive rats, and the responses demonstrated 3- to 5-fold (P < 0.05) increments compared to control at the doses of 10 and 30 ng/kg/min. However, in the two strains of rats, attenuation of natriuresis occurred with the highest infusion dose of 100 ng/kg/min and was probably related to the large decreases in MAP of 17-23 mmHg at this dose of the peptide. The present results indicate the ProANF31-67 has important hemodynamic and renal effects in hypertension and may represent one compensatory mechanism involved in this disease.

title: REGULATION OF COLLECTING DUCT Na+ REABSORPTION BY ANP 31–67
abstract: 1. The bulk of studies of the actions of atrial natriuretic peptides (ANP) have focussed on the carboxyterminal derivative (ANP 99–126) of the prohormone (ANP 1–126), but recent evidence indicates that an additional peptide derived from ANP 1–126, namely, ANP 31–67 also circulates, and has natriuretic actions.

title: Comparison of vessel dilator and long-acting natriuretic peptide in the treatment of congestive heart failure.
abstract: Long-acting natriuretic peptide (LANP; proANF 1-30) and vessel dilator (proANF 31-67) enhance sodium and water excretion in healthy human beings. The current investigation was designed to compare the beneficial effects of LANP and vessel dilator in persons with congestive heart failure (CHF).



LANP and vessel dilator (100 ng/kg body weight/min, respectively) were given intravenously for 60 minutes to subjects with New York Heart Association class III CHF (n = 17) while their urine volume and sodium and potassium excretion were monitored. Vessel dilator increased urine flow more than 5-fold, which was still increased (P <.001) 3 hours after stopping its infusion. Vessel dilator enhanced sodium excretion 3-fold in subjects with CHF (P <.01), which was still significantly (P <.01) elevated 3 hours after infusion. The effects of LANP were diminished, with urine flow only increasing 2-fold (P <.05). The fractional excretion of sodium increased maximally 6-fold secondary to vessel dilator and 3-fold with LANP. The CHF control patients had no changes in the above parameters. Part of the diminished response to LANP was found to be caused by its rapid decrease in the circulation of individuals with CHF.



These results indicate that vessel dilator has significant beneficial diuretic and natriuretic properties, which are not diminished, whereas the effects of LANP are diminished in human beings with CHF compared with healthy individuals.

title: Vessel dilator enhances sodium and water excretion and has beneficial hemodynamic effects in persons with congestive heart failure.
abstract: Vessel dilator, a 37-amino acid peptide hormone synthesized in the heart, enhances urine flow 4- to 12-fold and sodium excretion 3- to 6-fold in healthy humans. The present investigation was designed to determine whether vessel dilator might have similar beneficial effects in persons with congestive heart failure (CHF).



Vessel dilator (100 ng/kg body weight per minute) given intravenously for 60 minutes to NYHA class III CHF subjects increased urine flow 2- to 13-fold, which was still increased (P<0.001) 3 hours after its infusion was stopped. Vessel dilator enhanced sodium excretion 3- to 4-fold in CHF subjects (P<0.01), which was still significantly (P<0.01) elevated 3 hours after infusion. Vessel dilator decreased systemic vascular resistance 24%, pulmonary vascular resistance 25%, pulmonary capillary wedge pressure 33%, and central venous pressure 27% while increasing cardiac output 34%, cardiac index 35%, and stroke volume index 24% without significantly affecting heart rate or pulmonary artery pressure in the CHF subjects. The control CHF patients did not have any changes in the above parameters.



These results indicate that vessel dilator has significant beneficial diuretic, natriuretic, and hemodynamic properties in humans with congestive heart failure.

title: Negative feedback of atrial natriuretic peptides.
abstract: The present investigation was designed to determine whether atrial natriuretic peptides consisting of amino acids 1-30 [i.e. pro-ANF-(1-30)], 31-67 [i.e. pro-ANF(31-67)], 79-98 [i.e. pro-ANF-(79-98)], and 99-126 [i.e. atrial natriuretic factor (ANF)] of 126-amino acid ANF prohormone have a negative feedback on their own and each others' release. Thirty healthy human subjects were studied with infusion of 100 ng/kg BW.min for 60 min of each of the respective peptides. Pro-ANF-(1-30) decreased the circulating concentrations of pro-ANF-(31-67) and ANF 51% and 89%, respectively. Pro-ANF-(31-67) decreased the circulating concentration of ANF by 55% and the peptides immunologically recognized by the pro-ANF-(1-30) RIA by 58% [this assay recognizes pro-ANF-(1-30) (50%) and pro-ANF-(1-98) (50%)]. Pro-ANF-(79-98) decreased the circulating concentration of ANF by 40%, pro-ANF-(31-67) by 31%, and the peptides recognized by the pro-ANF-(1-30) RIA by 46%. ANF decreased the circulating concentration of pro-ANF-(31-67) by 40% and the peptides recognized by pro-ANF-(1-30) RIA by 38%. Infusion of pro-ANF-(1-30), -(31-67), -(79-98), and -(99-126) also decreased the excretion of the other atrial natriuretic peptides measured in the urine by 32-84%. Infusion of vehicle only did not result in any decrease in these atrial natriuretic peptides in either plasma or urine. These data taken together indicate that each of the respective atrial natriuretic peptides inhibits the release, rather than breakdown, of each other, as increased breakdown would have resulted in their urinary concentrations being increased. This study further indicates that because pro-ANF-(1-98) was decreased in the circulation secondary to pro-ANF-(31-67) and pro-ANF-(79-98) infusions, they inhibit their own release, as they are both derived from pro-ANF-(1-98).

title: Three Peptides From the Atrial Natriuretic Factor Prohormone Amino Terminus Lower Blood Pressure and Produce Diuresis, Natriuresis, and/or Kaliuresis in Humans
abstract: BackgroundThree peptides consisting of amino acids 1-30, 31-67, and 79-98 of the 126–amino acid atrial natriuretic factor prohormone (proANF), which have blood pressure-lowering, diuretic, natriuretic, and/or kaliuretic properties in animals, were investigated to determine if they have similar properties in humans. Methods and ResultsThirty-six healthy, normotensive human volunteers (18 men and 18 women, ages 20 to 58 years) were divided into six similar groups based on age, sex, weight, blood pressure, and heart rate. After a 60-minute baseline period, 100 ng of proANFs 1-30, 31-67, 79-98, or ANF/kg body wt per minute was given intravenously for 60 minutes followed by a 3-hour postinfusion data collection period. Each of the atrial natriuretic peptides decreased systolic and diastolic blood pressures (P<.05), with proANF 31-67 causing the largest decrease. Urine flow increased 4- to 12-fold and was still significantly increased (P<.01) for 2 to 3 hours after stopping the respective infusions of proANFs 1-30, 31-67, and 79-98. Atrial natriuretic factor (ANF) increased urine flow 4- to 11-fold but by 2 hours after infusion was significantly increased in only 1 of 6 subjects. Sodium excretion increased 3-to 8-fold, 3- to 6-fold, 0- to 2-fold (NS), and 3- to 11-fold, respectively, with proANFs 1-30, 31-67, 79-98, and ANF. Natriuretic effects of proANFs 1-30 and 31-67 were significantly prolonged (P<.001) compared with ANF. ProANFs 1-30, 31-67, 79-98, and ANF increased potassium excretion 2- to 3-fold, 0-fold, 3- to 4-fold, and 2-fold, respectively. High-performance gel permeation chromatography followed by the respective radioimmunoassays revealed that proANFs 1-30, 31-67, 79-98, and 68-98, as well as ANF circulate as distinct peptides. ConclusionsProANFs 1-30, 31-67, and 79-98, as well as ANF have significant blood pressure-lowering and diuretic properties. ProANFs 1-30 and 31-67 also have natriuretic properties in humans that are significantly (P<.001) prolonged compared with ANF. ProANF 79-98, although not possessing any natriuretic property, is the strongest stimulator of potassium excretion of the four atrial natriuretic peptides.

title: Analysis of peptides derived from Pro Atrial Natriuretic Peptide that circulate in man and increase in heart disease.
abstract: The present investigation was designed to determine the levels and circulating forms of peptides derived from Pro Atrial Natriuretic Peptide (ProANP) and to assess their usefulness as markers for severity of heart disease. A sensitive and specific "two-site" immunoradiometric assay (IRMA) for the measurement of C-terminal ProANP 99-126 (alpha ANP) and two radioimmunoassays (RIAs) for the measurement of N-terminal ProANP 31-67 and ProANP 79-98 were developed. Immunoassays were validated by measurement of circulating peptide concentrations in 15 normal volunteers and 44 patients with varying degrees of heart disease. Mean concentrations of immunoreactive (ir) alpha ANP, ProANP 79-98 and ProANP 31-67 in normal volunteers (n = 15) were 8.5 +/- 1.1, 143 +/- 16 and 587 +/- 83 pmoles/l, respectively, increasing in patients with mild heart disease (NYHA I to II; n = 22) to 17.1 +/- 2.1, 691 +/- 197 and 2160 +/- 540 pmoles/l with greatest increases being observed in patients with severe heart disease (NYHA III to IV; n = 22) of 103 +/- 23, 4550 +/- 590 and 10,600 +/- 1350 pmoles/l, respectively. RP-HPLC of pooled plasma revealed peaks corresponding to alpha ANP, beta ANP, ProANP 1-126, ProANP 1-98, ProANP 31-67 and ProANP 79-98, all apparently increased in heart disease. In conclusion, using a series of immunoassays, we observed the graded increase of alpha ANP, irProANP 31-67 and irProANP 79-98 with increasing severity of heart disease. All peptides proved useful markers, but only ProANP 79-98 levels were able to distinguish patients with mild heart disease (NYHA I) from normals. Finally, RP-HPLC analysis indicated that ProANPs 31-67 and 79-98 circulate as distinct entities, in addition to ProANP 1-98.

title: Increased Release of the N-Terminal and C-Terminal Portions of the Prohormone of Atrial Natriuretic Factor During Immersion-Induced Central Hypervolemia in Normal Humans 1
abstract: The role of peptides from the N terminus and C terminus of the 126 amino acid atrial natriuretic factor (ANF) prohormone in modulating renal sodium and water handling has not been defined. Since water immersion to the neck (Nl) provides an acute central volume expansion identical to that produced by 2 liters of saline but without plasma compositional change, immersion to the neck was used to assess the N-terminal and C-terminal portions of the ANF prohormone response to acute central blood volume expansion in seven seated sodium-replete normal subjects. Both the C terminus, which contains amino acids 99– 126 and is identical to ANF, and the whole N terminus (i.e., amino acids 1–98) increased promptly with Nl and peaked after 1 hr of immersion. A M, 3900 peptide from the midportion of the N terminus consistent with amino acids 31–67 (i.e., pro-ANF-31–67) also increased with Nl and followed a pattern of increasing circulating concentration nearly identical to that of the whole N terminus of the prohormone, except that its maximal concentration was at the second hour of the 3 hr of Nl. With cessation of immersion, ANF decreased to preimmersion levels within 1 hr whereas the N terminus and pro-ANF-31–67, although their circulating concentrations were decreasing, were still significantly elevated at 1 hr. These findings suggest that the increase in plasma ANF, the N terminus of the ANF prohormone, and pro-ANF-31–67 from the midportion of the N terminus, with natriuretic properties similar to ANF, contribute to the natriuretic response to Nl, implying a physiologic role for these atrial peptides in modulating volume homeostasis in humans.

title: Effect of haemodialysis on plasma levels of brain natriuretic peptide in patients with chronic renal failure.
abstract: 1. Plasma human brain natriuretic peptide-like immunoreactivity (hBNP-li) was measured in ten patients with chronic renal failure before and after 4 h of haemodialysis. 2. Plasma hBNP-li was elevated in all patients before dialysis (mean +/- SEM 21.0 +/- 3.8 pmol/l) compared with healthy control subjects (1.3 +/- 0.2 pmol/l, n = 11), but showed considerable inter-patient variability. Before dialysis plasma hBNP-li bore no relationship to the serum creatinine level or to the mean blood pressure. 3. Plasma hBNP-li fell significantly (P = 0.04) during 4 h of haemodialysis. The fall in plasma hBNP-li correlated significantly with the degree of postural blood pressure drop (r2 = 0.44, P = 0.05) and with the fall in body weight (r2 = 0.64, P less than 0.01) after haemodialysis. In all patients, plasma hBNP-li at the end of treatment remained above that in healthy subjects. 4. There was no significant correlation between the fall in plasma hBNP-li and the fall in serum creatinine level, and between the fall in plasma hBNP-li and the fall in supine systolic or diastolic blood pressure, during haemodialysis. 5. We have shown that plasma hBNP-li is elevated in patients with chronic renal failure and is decreased during haemodialysis. The fact that the plasma hBNP-li was not reduced to normal by haemodialysis despite restoration to normovolaemia gives tentative support to the view that, in addition to hypervolaemia, another factor may also be responsible for the elevated plasma hBNP-li seen in these patients.

title: Inhibition of aldosterone production by an atrial extract.
abstract: Crude extracts of rat atria reduced the basal amount of aldosterone released from rat zona glomerulosa cells and partially inhibited aldosterone stimulation by adrenocorticotropic hormone and angiotensin II. The destruction of this activity by trypsin suggests that the active factor is a peptide, possibly atrial natriuretic factor. These data suggest that atrial natriuretic factor affects sodium excretion by the kidneys both directly and through the inhibition of aldosterone production.

title: Effects of auriculin (atrial natriuretic factor) on blood pressure, renal function, and the renin-aldosterone system in dogs.
abstract: Auriculin is a potent vasoactive and natriuretic peptide that was recently isolated and purified from rat atrial tissue. Since this peptide could be of great importance for renal, cardiovascular, and volume homeostasis, its functional properties have been characterized in dogs. The effects of synthetic auriculin on renal function, mean blood pressure, plasma renin activity, renin secretory rate, and plasma aldosterone levels were determined. Auriculin was administered intravenously as a prime (1.0 microgram/kg body weight) and constant infusion (0.1 microgram per minute/kg body weight for one hour) to five anesthetized dogs. In addition, two conscious dogs were used to verify some of the results obtained in anesthetized dogs. Auriculin decreased mean blood pressure from 134 +/- 5 to 122 +/- 4 mm Hg (p less than 0.05, paired t test) and increased glomerular filtration rate (25.5 +/- 2.7 to 32.4 +/- 4.1 ml per minute per kidney, p less than 0.05), diuresis (0.21 +/- 0.03 to 1.06 +/- 0.14 ml per minute per kidney, p less than 0.05), natriuresis (38 +/- 0.6 to 187 +/- 35 mueq per minute per kidney, p less than 0.05), and kaliuresis (14.8 +/- 1.6 to 35.7 +/- 6.3 mueq per minute per kidney, p less than 0.05). These effects were sustained throughout the infusion of auriculin and were entirely reversible. Renal plasma flow increased transiently for one to two minutes, and then returned to or below control levels. Urine osmolality decreased by 40 percent (p less than 0.05) whereas free water clearance remained unchanged (p less than 0.05). Auriculin reversibly decreased plasma renin activity (11.6 +/- 2.3 to 3.6 +/- 1.2 ng/ml per hour, p less than 0.05), renin secretory rate (895 +/- 313 to 255 +/- 28 ng per hour per minute, p less than 0.05), and plasma aldosterone levels (8.4 +/- 1.6 to 3.6 +/- 0.7 ng/dl, p less than 0.05), whereas plasma cortisol levels remained unchanged. These results demonstrate that auriculin has a unique combination of functional properties, increasing glomerular filtration rate, diuresis, and natriuresis, without a sustained increase in total renal blood flow, and lowering blood pressure, plasma renin levels, renin secretory rate, and plasma aldosterone levels. These properties suggest an important potential role for atrial natriuretic peptides in the regulation of renal function, extracellular volume, and blood pressure.

title: Effect of synthetic atrial natriuretic factor on aldosterone secretion in the rat.
abstract: Direct in vivo measurements of aldosterone secretion were made before and after infusion of synthetic rat atrial natriuretic factor (ANF) into anesthetized rats with markedly different levels of plasma renin activity. Infusion of ANF peptide at 350 ng . kg-1 . min-1 significantly decreased aldosterone secretion by 32% and plasma renin activity by 55% in rats that had been maintained on a normal-sodium diet. Similar reductions in aldosterone secretion and plasma renin activity were observed in hyperreninemic rats after chronic sodium restriction. Infusion of ANF at 350 ng . kg-1 . min-1 into anephric rats with low circulating levels of renin did not significantly decrease the secretion of aldosterone. Increasing the ANF peptide infusion dose fivefold in these anephric rats did result in a significant reduction in aldosterone secretion, but this higher dose also produced significant decreases in blood pressure not observed with the lower dose of ANF. These results demonstrate that infusion of synthetic ANF decreases the secretion rate of aldosterone in the rat, but the ability of ANF to decrease aldosterone secretion is attenuated when circulatory levels of renin and hence angiotensin II are very low. The data suggest that although ANF can exert a direct inhibitory effect on the adrenal glomerulosa in larger doses that also produce systemic cardiovascular effects, one physiological mechanism by which ANF suppresses aldosterone secretion may be related indirectly to the inhibition of renin release.

title: Kaliuretic peptide and long acting natriuretic peptide as well as atrial natriuretic factor inhibit aldosterone secretion.
abstract: The present investigation was designed to determine whether atrial natriuretic peptides consisting of amino acids 1-30 (long acting natriuretic peptide), 31-67 (vessel dilator) and 79-98 (kaliuretic peptide) as well as 99-126 (atrial natriuretic factor (ANF)) of the 126 amino acid ANF prohormone inhibit aldosterone secretion. Thirty healthy human subjects were studied following infusion of 100 ng/kg body weight/min for 60 min of each of the respective peptides. Kaliuretic peptide decreased plasma aldosterone concentration by the greatest amount (6-fold) and plasma aldosterone was still significantly decreased (P < 0.001) three hours after stopping the infusion. In contrast, within 30 min of cessation of the ANF infusion, plasma aldosterone levels had returned to pre-infusion values. Long acting natriuretic peptide also significantly (P < 0.01) decreased plasma aldosterone levels which remained significantly (P < 0.001) decreased 3 h after cessation of infusion. Vessel dilator did not decrease plasma aldosterone levels. Kaliuretic peptide, ANF and long acting natriuretic peptide also decreased (P < 0.01) urinary aldosterone concentrations. None of these peptides changed the plasma potassium concentration. We conclude that two new peptide hormones (long acting natriuretic peptide and kaliuretic peptide) inhibit aldosterone secretion. The length of time that aldosterone secretion is inhibited following kaliuretic peptide and long acting natriuretic peptide infusion is significantly longer (P < 0.001) than following ANF infusion.

title: Modulation of renin secretion by atrial natriuretic factor prohormone fragment 31-67.
abstract: Earlier studies have indicated that the atrial natriuretic factor prohormone fragment 31-67 (Pro ANF31-67) has important effects for the promotion of sodium excretion and vasodilation in several animal species. However, the mechanisms for the natriuretic actions of Pro ANF31-67 are not completely defined. In the present study, the effects of synthetic Pro ANF31-67 on renin secretion were examined in sodium-depleted, anesthetized dogs with a single intact kidney (n = 5).



After 3 20-minute control renal clearance periods, synthetic dog Pro ANF31-67 was given intrarenally at a sustained dose of 0.03 microg/kg/min for 3 20-minute experimental intervals, and after discontinuation of the peptide infusion, 3 final 20-minute recovery periods were determined.



Sustained intrarenal infusions of the Pro ANF31-67 produced striking decrements (p<0.05) in renin secretion, from a control value of 1418 +/- 243 to 401 +/- 223 ng of angiotensin I/min. This 66% fall in renin secretion was associated with significant (P < 0.05) increases in creatinine clearance (40%), renal blood flow (8%), urine flow (50%), and sodium excretion (17%).



It is suggested that this inhibition of renin secretion was mediated, at least in part, in response to a ProANF31-67-induced increment in the sodium load delivered to the macula densa. An interaction of the peptide with the renal vascular receptor for suppression of renin release is also possible. ProANF31-67 may represent an important hormonal mechanism involved in the regulation of body-fluid balance.

title: Effects of kaliuretic peptide on sodium and water excretion in persons with congestive heart failure.
abstract: Kaliuretic peptide, a 20-amino acid peptide hormone synthesized in the heart, enhances urine flow twofold, whereas atrial natriuretic peptide (ANP) enhances urine flow four- to 11-fold in healthy persons. The present investigation was designed to (1) determine whether kaliuretic peptide may have beneficial diuretic effects in persons with congestive heart failure (CHF), and (2) compare its beneficial effects with ANP in the treatment of CHF. Kaliuretic peptide (100 ng/kg body weight/min) given intravenously for 60 minutes to subjects with New York Heart Association class III CHF increased urine flow fourfold (p <0.001), which was maximal 212 hours after its infusion was stopped. Kaliuretic peptide enhanced sodium excretion threefold in subjects with CHF (p <0.01). Kaliuretic peptide increased the urinary excretion rate of potassium ion and fractional excretion of potassium 3.5- and twofold (p <0.05), respectively. ANP (same concentration) did not significantly enhance urine flow. ANP enhanced sodium excretion two- to sixfold in half of the CHF subjects, whereas it had no effect on sodium excretion in the other half. ANP did not significantly increase fractional excretion of sodium but did increase fractional excretion of potassium (p <0.05) during the first 20 minutes of its infusion. ANP-infused patients with CHF became hypotensive. None became hypotensive secondary to kaliuretic peptide. These data indicate that the diuretic properties of kaliuretic peptide in persons with CHF, as opposed to those of ANP, are not diminished (but rather are increased) compared with their effects in healthy persons. In patients with CHF, kaliuretic peptide causes a natriuresis-a feature not observed in those without sodium retention.

title: Isolation and structural analysis of “Urodilatin”, a new peptide of the cardiodilatin-(ANP)-family, extracted from human urine
abstract: SummaryTwo 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 1 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.

title: Atrial Natriuretic Peptide Increases Urodilatin in the Circulation
abstract: Urodilatin is a 32-amino-acid (AA) peptide formed in the kidney.  High-performance gel permeation chromatography and high-pressure liquid chromatography evaluation of plasma followed by sensitive urodilatin and atrial natriuretic peptide (ANP) assays revealed that urodilatin does circulate distinctly from ANP.  Urodilatin circulates at very low levels (i.e 9–12 pg/ml). Infusion of ANP increased the circulating concentration of urodilatin 135-fold (p < 0.001), suggesting that some of the effects of ANP may be mediated by urodilatin while long-acting natriuretic peptide, vessel dilator, and kaliuretic peptide did not affect urodilatin in healthy humans (n = 30). Only ANP decreased the renal clearance of urodilatin (60–75%, p < 0.01). Urodilatin was metabolized into peptides smaller than 5 AAs as well as excreted intact into urine.  Urodilatin circulates and is increased by ANP in humans.

title: A new natriuretic peptide in porcine brain
abstract: Atrial natriuretic peptide (ANP), a hormone secreted from mammalian atria, regulates the homoeostatic balance of body fluid and blood pressure13. ANP-like immunoreactivity is also present in the brain, suggesting that the peptide functions as a neuro-peptide4,5. We report here identification in porcine brain of a novel peptide of 26 amino-acid residues, eliciting a pharmacological spectrum very similar to that of ANP, such as natriuretic-diuretic, hypotensive and chick rectum relaxant activities. The complete amino-acid sequence determined for the peptide is remarkably similar to but definitely distinct from the known sequence of ANP1,3,6, indicating that the genes for the two are distinct. Thus, we have designated the peptide 'brain natriuretic peptide' (BNP). The occurrence of BNP with ANP in mammalian brain suggests the possibility that the physiological functions so far thought to be mediated by ANP may be regulated through a dual mechanism involving both ANP and BNP

title: Disposition of vessel dilator and long-acting natriuretic peptide in healthy humans after a one-hour infusion.
abstract: The present investigation was designed to determine half-lives, distribution phases and metabolic clearance of two new cardiac peptide hormones in humans. Long-acting natriuretic peptide (LANP) and vessel dilator were infused at 100 ng/kg of b.wt./min concentrations for 60 min with their respective concentrations measured by specific radioimmunoassays in plasma during and for 3 hr after infusion. The half-life of vessel dilator was 107 min, whereas the half-life of LANP was 28 min. The average time that the respective peptides were retained in the body (mean residence time) was 214 +/- 34 min for vessel dilator and 178 +/- 12 min for LANP, which indicates that they are widely distributed outside the initial space (i.e., circulation). The metabolic clearance normalized to 1.73 m2 body surface area was 241 ml/min for vessel dilator and 249 ml/min for LANP. The total body clearance normalized to 1.73 m2 body surface area was 130 ml/min for vessel dilator and 293 ml/min for LANP. The significantly (P < .001) longer half-lives and slower metabolic clearance of LANP and vessel dilator compared with atrial natriuretic factor (half-life, 2.5 min, metabolic clearance, 582-2,581 ml/min/1.7 m2) explain why these peptides circulate at concentrations 15- to 24-fold higher than atrial natriuretic factor in healthy humans.

title: C-type natriuretic peptide (CNP): a new member of natriuretic peptide family identified in porcine brain.
abstract: Two types of natriuretic peptide, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), very similar to each other in structure and in pharmacological effect, are known to be present in mammalian heart and brain. In our present survey for unidentified peptides in porcine brain extracts, we found a new peptide of 22 amino acid residues, eliciting a potent relaxant activity on chick rectum. The amino acid sequence determined for the peptide shows remarkable similarity to those of ANP and BNP, especially in the 17-residue sequences flanked by two cysteine residues. The peptide shows a pharmacological spectrum similar to ANP and BNP. Thus, the peptide was designated "C-type natriuretic peptide (CNP)", the third member to join the natriuretic peptide family. In contrast to ANP and BNP, CNP terminates in the second cysteine residue, lacking a further C-terminal extension.

title: Characterization of immunoreactive brain natriuretic peptide in human cardiac atrium.
abstract: Based on cDNA sequence data for human brain natriuretic peptide (BNP) precursor (1), a radioimmunoassay (RIA) system highly specific to human BNP (hBNP) was developed and used to characterize immunoreactive (ir-) hBNP in cardiac atrium. Gel filtration of ir-hBNP in atrium indicated that ir-hBNP was mainly comprised of two molecular forms of 13-15K and 4K. In reverse phase high performance liquid chromatography (HPLC), the low molecular weight (MW) ir-hBNP emerged as a single peak at an elution time identical to that of synthetic hBNP-32. The high MW ir-hBNP was also eluted as a single peak. On the other hand, tissue concentrations of ir-hBNP in cardiac atria were found to be 9.98-593.22 pmol/g in 13 specimens, being about 1/150 the concentration of ir-human atrial natriuretic peptide (hANP). These results demonstrate that hBNP is present as a peptide in human heart, suggesting that hBNP is secreted from heart and functions together with hANP as a hormone.

title: Ameliorated glomerular injury in mice overexpressing brain natriuretic peptide with renal ablation.
abstract: Brain natriuretic peptide (BNP) is a cardiac hormone produced by the ventricle, and its secretion is markedly increased in heart failure, hypertension, and renal failure. Transgenic mice that overexpress BNP in the liver (BNP-Tg) were recently generated, resulting in low BP. To elucidate the role of BNP in renal pathophysiology, the effect of chronic excess of BNP in transgenic mice on glomerular injury after subtotal nephrectomy induced by resection of the renal poles was examined. After nephrectomy, glomerular cross-sectional areas in control nontransgenic mice markedly increased as compared with those in sham-operated mice (+81 +/- 7%), whereas there was only a modest increase in BNP-Tg (+10 +/- 6%). Expansion of the mesangial area and increase in the intraglomerular cell number were also inhibited in BNP-Tg. Glomerular expressions of transforming growth factor-beta and fibronectin were increased with hypertrophy and were significantly suppressed in BNP-Tg. Furthermore, increases in the urinary albumin excretion and BP were significantly ameliorated in BNP-Tg. Chronic hydralazine treatment in nephrectomized nontransgenic mice failed to inhibit glomerular hypertrophy. These findings indicate that the chronic excess of BNP in mice ameliorates glomerular hypertrophy and mesangial expansion after renal ablation. The results also suggest that the observed effects of natriuretic peptides under reduced renal mass are not due merely to systemic BP reduction and may be therapeutically applicable in various renal diseases.

title: Endogenous ANP augments fractional excretion of Pi, Ca, and Na in rats with reduced renal mass.
abstract: Atrial natriuretic peptide (ANP) infusion increases fractional excretion of many solutes including sodium, chloride, bicarbonate, phosphate, calcium, and magnesium. Because fractional excretion of these solutes increases with advancing renal disease, and because plasma ANP levels are known to be elevated in chronic renal failure, we sought to determine whether ANP mediates increased solute excretion rates per nephron in rats following extensive renal ablation, a model of chronic renal failure. Because sodium restriction decreases plasma ANP levels in the setting of reduced renal mass, we also determined the effect of sodium restriction on sodium, phosphate, calcium, and magnesium excretion rates in rats with 5/6 nephrectomy (NX). We also assessed whether high endogenous ANP levels influence fractional sodium, phosphate, calcium, and magnesium excretion in rats with 5/6 NX, by inhibiting ANP action via infusion of a high-affinity ANP antiserum. Whole-kidney glomerular filtration rate in 5/6 NX rats averaged approximately one-third that of shams, and plasma ANP levels were significantly elevated in these rats above those of shams, but to a lesser extent in rats on low- vs. high-salt intakes. Fractional sodium, phosphate, and calcium, but not magnesium excretion rates were significantly greater in 5/6 NX rats on the higher sodium intake compared with those in 5/6 NX rats on the lower sodium intake. Moreover, in 5/6 NX rats on the higher sodium intake, ANP antiserum significantly reduced fractional sodium, phosphate, and calcium excretion, but was without effect on magnesium excretion. These data implicate endogenous ANP in promoting the adaptive increase in sodium, phosphate, calcium, but not magnesium excretion per nephron in chronic renal disease.

title: Upregulation of atrial natriuretic peptide gene expression in remnant kidney of rats with reduced renal mass.
abstract: Atrial natriuretic peptide (ANP) is synthesized in the kidney but its physiologic significance there is unclear. To determine whether renal expression of the ANP gene is regulated, renal ANP mRNA expression was assessed in remnant kidneys after 5/6 nephrectomy in Munich-Wistar rats. In normal sodium intake groups, ANP mRNA expression in the remnant kidney was significantly increased by 5.0 +/- 0.8-fold (n = 7, mean +/- SEM) at 4 d when compared with sham-operated controls (n = 6, all sham-operated groups) (*P < 0.001 by Scheffe's test) and by 28.3 +/- 5.1-fold at 14 d. This latter response was markedly diminished to 7.6 +/- 2.1-fold (n = 7, versus sham) in rats maintained on a low sodium diet. At 4 d, on the other hand, no significant downregulation was observed with dietary sodium restriction. Because natriuretic peptides have previously been shown by us to play a major role in the adaptive responses of remnant nephrons to renal mass ablation, these data suggest that ANP of renal origin may contribute to the overall mechanism for enhancing sodium excretion in the face of declining nephron number.

title: Effects of natriuretic peptide receptor inhibition on remnant kidney function in rats.
abstract: To identify the contribution of natriuretic peptide (NP) activity to the adaptative increases in glomerular filtration rate (GFR), effective renal plasma flow rate (ERPF) and fractional sodium excretion (FENa) observed in the remnant kidney, we investigated the acute effects of administering HS-142-1 (HS), a potent NP receptor antagonist, in 5/6th nephrectomized (NPX) rats. In addition to normal sodium intake, high or low sodium intakes were used to stimulate or suppress, respectively, endogenous NP activity in NPX rats. In rats three days after NPX on high sodium, HS (20 mg/kg bolus i.v.) reduced GFR from 0.55 +/- 0.05 to 0.35 +/- 0.04 ml/min; ERPF from 1.83 +/- 0.19 to 1.53 +/- 0.16 ml/min; and FENa from 7.1 +/- 1.1 to 1.6 +/- 0.4%, without affecting MAP. Similar changes of lesser magnitude were observed in NPX rats on normal sodium intake. By contrast, GFR, ERPF, FENa and MAP were unchanged following HS in NPX rats on low sodium intake, suggesting that the magnitude of responses to HS is dependent upon the expected levels of activity of NP. We conclude that in anesthetized rats, natriuretic peptides contribute to the compensatory increases in GFR, ERPF and FENa observed in the remnant kidney under normal and salt-replete conditions.

title: Low-dose C-type natriuretic peptide does not affect cardiac and renal function in humans.
abstract: In experimental animals, C-type natriuretic peptide (CNP) has vasodilating, hypotensive, and natriuretic activities. The role of circulating CNP in the overall regulation of cardiac and renal function in humans is less defined, in both health and disease. We measured cardiac volumes, diastolic and systolic functions, systemic (Doppler echocardiography) and renal hemodynamics, intrarenal sodium handling (lithium clearance method), plasma and urinary cGMP, plasma renin concentration, and plasma aldosterone level in six healthy volunteers (mean age, 33+/-3 years) receiving CNP (2 and 4 pmol/kg per minute for 1 hour each) in a single-blind, placebo-controlled, random-order, crossover study. During CNP infusion, plasma CNP increased from 1.17+/-0.23 to 41.52+/-4.61 pmol/L (ie, 4- to 10-fold higher levels than those observed in disease states) without affecting plasma and urinary cGMP, cardiac volumes, dynamics of left and right heart filling, cardiac output, arterial pressure, renal hemodynamics, intrarenal sodium handling, sodium excretion, or plasma levels of renin and aldosterone. The finding that increments in plasma CNP within the pathophysiological range have no effects on systemic hemodynamics, renal function, or the renin-angiotensin system do not support the hypothesis that CNP may act as a circulating hormone in humans.

title: Bioactivity and metabolism of C-type natriuretic peptide in normal man.
abstract: C-Type natriuretic peptide (CNP) is a recently identified member of the natriuretic peptide family with potent vasodepressor activity in experimental animals. Specific CNP receptors and gene transcripts have been identified in human vascular tissues, but the bioactivity and metabolism of CNP in humans are unknown. Accordingly, we have studied the renal, hormonal, and hemodynamic responses in nine normal men (seated, nonfasting) receiving a morning infusion (2 h) of synthetic human CNP-22 (5 pmol/kg.min) or placebo in single blind, random order. To determine the vasodepressor action, the effect of a second identical (afternoon) infusion on the pressor and hormone responses to angiotensin-II (2, 4, and 8 ng/kg.min each for 30 min) was also studied. In the morning infusion, plasma CNP increased from undetectable baseline levels to plateau levels (mean, 60 +/- 6 pmol/L) at 30-120 min. The mean MCR was 4.8 +/- 0.7 L/min, and the t 1/2 (plasma) was 2.6 min. Compared with the effects of placebo, there were significant increases in plasma cGMP (P = 0.001) and plasma atrial natriuretic peptide (ANP; P = 0.02) and a significant decrease in plasma aldosterone (P = 0.007). No significant hemodynamic action or natriuresis was observed. During coinfusion of angiotensin-II, the expected pressor and aldosterone responses were not significantly altered by CNP. In contrast to atrial and brain natriuretic peptide, short term infusion of CNP in humans, achieving supraphysiological levels in plasma, are not vasodepressor or natriuretic. Increases in plasma ANP and plasma cGMP and inhibition of aldosterone may be due in part to competitive displacement by CNP of ANP in common degradative pathways.

title: C-type natriuretic peptide in chronic renal failure and its action in humans.
abstract: We have previously reported that C-type natriuretic peptide (CNP), the third member of the natriuretic peptide family, is produced in vascular endothelial cells and acts as an endothelium-derived relaxing peptide. To clarify the clinical significance of CNP in renal disorders, we examined the plasma level of CNP in patients with various cardiovascular diseases, including chronic renal failure (CRF) patients who were under hemodialysis therapy. We also investigated biological effects of intravenously-administered CNP (0.43 nmol/kg) by bolus injection from the peripheral vein in healthy volunteers and measured systemic hemodynamic variables, plasma levels of CNP, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), cGMP, aldosterone and also urine volume, urinary excretions of sodium, potassium, chloride and cGMP. The plasma CNP levels in healthy humans (N = 13) was 1.4 +/- 0.6 fmol/ml. In CRF patients, the plasma CNP significantly increased up to 3.0 +/- 1.1 fmol/ml. The administration of CNP elicited significant increase of plasma cGMP level (from 4.77 +/- 1.25 to 8.33 +/- 1.59 pmol/ml 15 min after the administration) and of urinary cGMP excretion (from 30.7 +/- 4.3 to 74.9 +/- 13.4 nmol/30 min). Intravenously-administered CNP exerted significant diuretic (% increase: +117 +/- 85.0), natriuretic, kalliuretic and chloriuretic actions with the increase of endogenous creatinine clearance. CNP also elicited significant hypotensive actions (delta BPs/delta BPd: -4.3 +/- 1.3/-4.1 +/- 1.0 mm Hg) with the concomitant increase of heart rate (+7.6 +/- 2.6 bpm). Plasma aldosterone concentration significantly decreased from 45.4 +/- 2.3 to 35.4 +/- 4.9 pg/ml 30 minutes after the administration. Taken together, these results suggest a role for CNP in human renal function.

title: Adrenomedullin: a novel hypotensive peptide isolated from human pheochromocytoma.
abstract: A novel hypotensive peptide was discovered in human pheochromocytoma by monitoring the elevating activity of platelet cAMP. Since this peptide is abundant in normal adrenal medulla as well as in pheochromocytoma tissue arising from adrenal medulla, it was designated "adrenomedullin". The peptide, consisting of 52 amino acids, has one intramolecular disulfide bond and shows slight homology with calcitonin gene related peptide. It was found to elicit a potent and long lasting hypotensive effect. The peptide circulates in blood in a considerable concentration, but it was not found in brain. These data suggest that adrenomedullin is a new hormone participating in blood pressure control. Occurrence of adrenomedullin indicates the possible existence of a novel system for circulation control.

title: Atrial natriuretic peptide increases adrenomedullin in the circulation of healthy humans.
abstract: Adrenomedullin (ADM) is a new 52 amino acid peptide originally isolated from extracts of human pheochromocytoma. ADM's biologic properties are nearly identical to those of atrial natriuretic peptides. Thus, the 4 peptide hormones originating from amino acids 1-30 [long acting natriuretic peptide], 31-67 [vessel dilator], 79-98 [kaliuretic peptide] and 99-126 [atrial natriuretic factor; ANF] of the 126 amino acid ANF prohormone as well as ADM have blood pressure lowering and diuretic properties. The present investigation was designed to determine if one or more of these 4 atrial natriuretic peptides increase adrenomedullin within the circulation of healthy humans. Infusion of 100 ng/kg body weight/minute for 60 minutes of the respective atrial peptides resulted in a 4-fold (P < 0.001) increase in the circulating concentration of adrenomedullin secondary to the ANF infusion but no increase in adrenomedullin with the long acting natriuretic peptide, vessel dilator, or kaliuretic peptide infusions. The four-fold increase of adrenomedullin in the circulation persisted throughout the infusion of ANF, but returned to pre-infusion levels within 30 minutes of stopping the ANF infusion. Infusion of 10 pg/kg body weight/minute for 60 minutes of ANF resulted in a 2 1/2-fold increase (P < 0.05) in the circulating concentration of adrenomedullin. There was a significant (P < 0.01) diuresis and blood pressure lowering effect with each of the atrial natriuretic peptides in the present investigation. This investigation suggests that 1) atrial natriuretic factor increases the release of adrenomedullin and 2) that the diuretic and blood pressure lowering effects previously attributed to atrial natriuretic factor may be partially due to adrenomedullin since both increased during the ANF infusion and both have similar biologic effects. As opposed to atrial natriuretic factor, adrenomedullin was not increased by long acting natriuretic peptide, vessel dilator, or kaliuretic peptide suggesting that their biologic effects do not involve adrenomedullin.

title: Secretion of Adrenomedullin by Renal Tubular Cell Lines
abstract: Adrenomedullin (AM) is a novel and potent vasodilator peptide originally isolated from human pheochromocytoma. The present study was designed to study whether AM is produced by and secreted from renal tubular cell lines and whether arginine vasopressin (AVP) affects AM secretion from these cell lines. Three renal tubular cell lines derived from different species (LLCPK1, MDCK, and MDBK) secrete AM-like immunoreactivity (AM-LI) into culture medium, the immunological and physicochemical properties of which are similar to that of synthetic human AM as evaluated by reverse-phase high-performance liquid chromatography. Among the three cell lines, AVP in combination with a phosphodiesterase inhibitor (isobutylmethylxanthine) stimulated AM-LI secretion most potently from MDCK cells in a time- and dose-dependent manner. In MDCK cells, a V2 receptor agonist (deamino-D-Arg8-vasopressin) dose-dependently stimulated AM-LI secretion in the same manner as AVP. Furthermore, the AVP-induced AM-LI secretion was blocked by a V2 receptor antagonist (OPC31260), but not by a V1 receptor antagonist (OPC21268). These data indicate that AM is secreted from renal tubular cell lines and that AVP stimulates AM secretion via V2 receptors, suggesting its autocrine/paracrine role in renal function.

title: Presence of Dendroaspis natriuretic peptide-like immunoreactivity in human plasma and its increase during human heart failure.
abstract: To determine whether Dendroaspis natriuretic peptide (DNP), a novel peptide isolated from the venom of the Dendroaspis angusticeps snake that contains a 17-amino acid disulfide ring structure similar to that in atrial, brain, and C-type natriuretic peptides, is present in normal human plasma and myocardium and whether, like the other natriuretic peptides, DNP-like immunoreactivity (DNP-LI) is activated in human congestive heart failure (CHF).



Circulating DNP-LI was assessed in 19 normal human subjects and 19 patients with CHF (New York Heart Association class III or IV) with a specific and sensitive radioimmunoassay for DNP with no cross-reactivity with the other natriuretic peptides. Immunohistochemical studies that used polyclonal rabbit anti-DNP antiserum were performed on human atrial myocardial tissue obtained from four patients with end-stage CHF who were undergoing cardiac transplantation and from three donor hearts at the time of transplantation.



We report that DNP-LI circulates in normal human plasma and is present in the normal atrial myocardium. In addition, DNP-LI is increased in the plasma of patients with CHF.



This study demonstrates, for the first time, the presence of a DNP-like peptide in normal human plasma and in the atrial myocardium. Additionally, these studies demonstrate increased plasma DNP-LI in human CHF. These results support the possible existence of an additional new natriuretic peptide in humans, which may have a role in the neurohumoral activation that characterizes human CHF.

title: Renal actions of synthetic dendroaspis natriuretic peptide.
abstract: Dendroaspis natriuretic peptide (DNP), recently isolated from the venom of the green Mamba snake Dendroaspis angusticeps, is a 38 amino acid peptide containing a 17 amino acid disulfide ring structure similar to that of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). DNP-like immunoreactivity (DNP-LI) was reported to be present in human plasma and atrial myocardium and to be elevated in human congestive heart failure. Although previously named DNP, it remains unknown if DNP is natriuretic or if is it present in canine plasma, urine, and atrial myocardium.



Studies were performed in vivo in anesthetized dogs (N = 6) using intravenous infusion of synthetic DNP at 10 and 50 ng/kg/min. Employing a sensitive and specific radioimmunoassay for DNP, the presence of DNP-like peptide was assessed in the canine plasma and urine before, during, and following the administration of exogenous synthetic DNP. Additionally, we performed immunohistochemical studies using the indirect immunoperoxidase method with polyclonal DNP antiserum in normal atrial myocardium (N = 10). Atrial concentrations of DNP-LI were also assessed.



We report that DNP is markedly natriuretic and diuretic, which, like ANP and BNP, is associated with the increase in urinary and plasma cGMP. DNP-like peptide is also detected in canine plasma, urine, and atrial myocardium.



These studies establish that DNP is a potent natriuretic and diuretic peptide with tubular actions linked to cGMP and that DNP may play a physiological role in the regulation of sodium excretion.

title: Immunocytochemical localization of proANF 1-30, proANF 31-67 and atrial natriuretic factor in the kidney.
abstract: ProANF [1-30 first 30 amino acids (a.a) of the 126 a.a atrial natriuretic factor (ANF) prohormone], ProANF 31-67 (a.a 31-67) as well as atrial natriuretic factor (a.a 99-126), of the ANF prohormone localized to the sub-brush border of the pars convoluta and pars rectus of the proximal tubules of hydrated and dehydrated rat kidneys with immunoperoxidase staining. Immunofluorescent studies revealed that each of these peptides and especially ProANF 31-67 had a strong predilection for the perinuclear region in the proximal and distal tubules. ProANFs 1-30, 31-67, and 99-126 (that is, ANF) also localized with both immunoperoxidase and immunofluorescent staining to the cortical collecting ducts, glomeruli, peritubular, and interstitial blood vessels. ProANF 31-67 immunoperoxidase staining was particularly striking in the elastica of the small and large interstitial arteries. The whole prohormone being present was suggested by immunological recognition in the rat kidney of both the N-terminus and C-terminus of the ANF prohormone by radioimmunoassays. The concentration of the N-terminus in the kidney was 1.0 +/- 0.03 ng/g of kidney weight, while the C-terminus of the ANF prohormone concentration was 0.4 +/- 0.01 ng/g of kidney tissue. These findings of a sub-brush border and perinuclear location of the N-terminal and C-terminal ANF prohormone peptides suggest that the atrial natriuretic factor prohormone may be synthesized in and/or the respective peptides are captured by the proximal tubules, but also to a lesser extent by the distal tubules of the kidney.

title: Immunocytochemical localization of ProANF 1-30, ProANF 31-67, atrial natriuretic factor and urodilatin in the human kidney.
abstract: Whether ProANF 1-30 [first 30 amino acids (a.a.) of the 126-a.a. atrial natriuretic factor (ANF) prohormone] and ProANF 31-67 (a.a. 31-67 of this prohormone) with their natriuretic and diuretic properties are present within the human kidney is unknown. In the present investigation, ProANFs 1-30 and 31-67 as well as ANF (a.a. 99-126) of the ANF prohormone localized to the subbrush border of the pars convoluta and pars recta of the proximal tubules of the human kidney with immunoperoxidase staining. Immunofluorescent studies revealed that each of these peptides had a strong inclination for the perinuclear region in the proximal and distal tubules. ProANFs 1-30, 31-67 and 99-126 (i.e. ANF) also localized with both immunoperoxidase and immunofluorescent staining to the coritcal collecting ducts, glomeruli, and peritubular and interstitial blood vessels. ANF immunoperoxidase staining was particularly striking in the endothelium of interstitial arteries and vasa recta. In the glomeruli, prominent staining was noted in the peripheral glomerular capillary wall and in some of the visceral epithelial cells. In contrast, urodilatin (i.e. a.a. 95-126 of the ANF prohormone) was not found in the proximal tubules, but weak staining was found in the distal tubules and interstitial vessels with some but not all glomeruli, peritubular vessels, cortical collecting tubules and outer medullary nephrons weakly staining by immunoperoxidase and immunofluorescent methods. The whole prohormone being present in the kidney was suggested by immunological recognition of both the N- and C-termini of the ANF prohormone by radioimmunoassays.(ABSTRACT TRUNCATED AT 250 WORDS)

title: Congestive heart failure: increased cardiac and extracardiac atrial natriuretic peptide gene expression.
abstract: The present investigation was designed to determine if atrial natriuretic peptide (ANP) gene expression increases in extracardiac as well as within the heart in congestive heart failure.



Congestive heart failure (CHF) was induced by producing cardiac hypertrophy secondary to an aortocaval fistula in Sprague-Dawley rats. To characterize this model, control and CHF rats had cardiac catheterizations and transthoracic echocardiography. ANP messenger RNA was measured by RNAase protection analysis in atria, ventricles, liver, colon, and stomach of CHF and sham rats and quantitated by 2-D scanning. The product of ANP gene expression was determined in each of these tissues with high performance-gel permeation chromatography. To help determine if increased degradation of atrial natriuretic peptides occur in congestive heart failure, the circulating concentrations and the excretion of the atrial natriuretic peptides into urine were measured by specific radioimmunoassays.



ANP steady-state mRNA increased 4.2 +/- 0.05 and 4.3 +/- 0.06-fold, respectively, in the antrum of the stomach and within the heart ventricle of CHF rats compared with age-matched sham rats. ANP gene expression was present but not increased in atria, liver, and gastrointestinal tract of the CHF rats. High-performance gel permeation chromatography revealed that the product of this ANP gene expression within the stomach and heart ventricle in CHF animals was the ANP prohormone. There was not any decrease in the metabolism of these peptides by the kidney in CHF.



ANP steady-state mRNA increases in extracardiac (i.e., stomach antrum) tissue as well as in the ventricle of the heart in CHF. The product of the ANP gene expression, i.e., the ANP prohormone is the same in the extracardiac tissues as within the heart. Whether the increased extracardiac ANP steady-state mRNA and its resultant increased atrial natriuretic peptides helps prevent bowel wall edema in CHF needs to be elucidated.

title: Increased atrial natriuretic peptide mRNA expression in the kidney of diabetic rats.
abstract: To investigate whether renal synthesis of atrial natriuretic peptide (ANP) is influenced in diabetes, we measured renal ANP mRNA levels, urine volume, urinary ANP and sodium excretion rates in streptozotocin (STZ)-induced diabetic rats. By using reverse transcription-polymerase chain reaction (RT-PCR) followed by Southern blot analysis, we found that renal cortical and outer medullary ANP mRNA levels in untreated diabetic rats were markedly increased as early as the second day after the onset of hyperglycemia and remained elevated for the entire 42-day study period. Plasma ANP concentrations in untreated diabetic rats were increased on the 42nd day, whereas plasma renin activity were suppressed. The urine volume, urinary ANP and sodium excretion rates in untreated diabetic rats were also significantly elevated on the second day and remained elevated for the entire 42-day study period. Urinary ANP excretion rates were well correlated with urine volume, and urinary sodium excretion rate in normal rats and diabetic rats on days 2, 4, 7, 14 and 42. Our results indicate that renal ANP mRNA expression is enhanced in diabetic rats, and that renal-synthesized ANP as one of regulators to handle water and sodium balance in diabetic rats is worthy of further investigation.

title: Localization, synthetic regulation, and biology of renal atriopeptin-like prohormone.
abstract: We recently demonstrated the synthesis and secretion of an atriopeptin (AP)-like prohormone in rat neonatal and adult cortical kidney cell cultures. However, these cultures contained proximal as well as distal tubular epithelial cells; thus characterization of the peptide synthetic cell was not possible. Also, by immunohistochemical techniques, we localized this AP-like prohormone to the distal cortical nephron in adult rat kidney. In this study, we examined further details of the kidney cortical cell type that expresses and secretes this AP-like peptide in adult renal cortical cell cultures, its regulation by adenylate cyclase via adenosine 3',5'-cyclic monophosphate (cAMP) generation, and its ability to stimulate guanylate cyclase. Tubular fragments were derived from cortical tissue of adult Sprague-Dawley rats and separated into four fractions on Percoll density gradient. Cell cultures generated from fraction 3 secreted 5- to 10-fold the amount of this renal peptide compared with fractions 2 and 4. Further cell culture characterization was performed by agonist-stimulated cAMP formation, kallikrein localization, and prostaglandin E2 formation. From these analyses, it was determined that tissue band 3 was enriched for distal cortical connecting tubules. To further evaluate whether mammalian distal nephron synthesizes an AP-like protein, we determined that two immortalized mouse cell lines, derived from either the distal convoluted tubule or cortical collecting tubule, synthesized a radiolabeled AP after being pulsed with [35S]-methionine.(ABSTRACT TRUNCATED AT 250 WORDS)

title: Plasma concentrations of immunoreactive-atrial natriuretic polypeptide in patients on hemodialysis.
abstract: Plasma concentrations of immunoreactive (IR)-atrial natriuretic polypeptide (ANP) were measured before and after hemodialysis (HD) as well as isolated ultrafiltration (UF) in 9 patients with end-stage renal disease. There were significant falls in plasma concentrations of IR-ANP during both UF (from 78.6 +/- 109.7 to 45.4 +/- 56.8 pg/ml; mean +/- SD; p less than 0.025) and HDs (from 84.7 +/- 48.6 to 35.0 +/- 28.4 (p less than 0.01) on first HD; from 73.7 +/- 74.2 to 31.8 +/- 21.8 pg/ml (p less than 0.01) on later HD). There were distinct positive correlations between blood pressures and plasma concentrations of IR-ANP. These results support the view that ANP is secreted mainly by the expansion of blood volume. The fall in plasma concentrations of IR-ANP after HD seems to be caused by the decrease of blood volume, but not by removal due to dialysis of the peptide. However, the physiological role of ANP in patients with end-stage renal disease remains unknown.

title: Change in plasma immunoreactive N-terminus, C-terminus, and 4,000-dalton midportion of atrial natriuretic factor prohormone with hemodialysis.
abstract: Plasma concentrations of the immunoreactive N-terminus, C-terminus and 4,000-dalton midportion of the N-terminus of the atrial natriuretic factor (ANF) prohormone were measured before and after hemodialysis in 13 patients with end-stage renal disease. There was a significant (p less than 0.001) fall in the mean plasma concentration of the C-terminus (i.e. ANF, amino acids 99-126 of the prohormone) from 123 +/- 25 to 80 +/- 22 fmol/ml (mean +/- SEM) with dialysis. The whole N-terminus, on the other hand, increased from 9,336 +/- 2,011 to 11,021 +/- 2,134 fmol/ml after dialysis (p less than 0.002). Pro ANF 31-67 (i.e. amino acids 31-67 of the prohormone) increased postdialysis from 27,775 +/- 4,300 to 31,040 +/- 4,840 fmol/ml (p less than 0.003). Only 1.5% of pro ANF 1-98 and pro ANF 31-67 were cleared by the dialyzer membrane while 15% of ANF crossed the membrane. Thus, with hemodialysis the C-terminus decreases while the N-terminus and pro ANF 31-67 from the midportion of the N-terminus of the ANF prohormone increase in plasma which is partially explained by their respective abilities to cross the dialyzer membrane.

title: Plasma concentrations and comparisons of brain natriuretic peptide and atrial natriuretic peptide in normal subjects, cardiac transplant recipients and patients with dialysis-independent or dialysis-dependent chronic renal failure.
abstract: 1. We have developed a radioimmunoassay for the measurement of immunoreactive brain natriuretic peptide (1-32) in human plasma. Simultaneous measurements of atrial natriuretic peptide have also been carried out to allow for direct comparison between circulating brain natriuretic peptide and atrial natriuretic peptide. Plasma levels of immunoreactive brain natriuretic peptide (means +/- SEM) were 1.1 +/- 0.1 pmol/l in 36 normal healthy subjects and were significantly elevated in cardiac transplant recipients (18.8 +/- 3.9 pmol/l, n = 12) and in patients with dialysis-independent (8.8 +/- 1.5 pmol/l, n = 11) or dialysis-dependent (41.6 +/- 8.8 pmol/l, n = 14) chronic renal failure. Similarly, in these groups of patients plasma levels of atrial natriuretic peptide were also significantly raised when compared with those in the group of normal healthy subjects. 2. The plasma level of atrial natriuretic peptide was significantly higher than that of brain natriuretic peptide in normal subjects and in patients with dialysis-independent chronic renal failure, with ratios (atrial natriuretic peptide/brain natriuretic peptide) of 2.8 +/- 0.2 and 2.2 +/- 0.3, respectively. However, in both cardiac transplant recipients and patients on dialysis plasma levels of atrial natriuretic peptide and brain natriuretic peptide were similar, with ratios of 1.3 +/- 0.2 and 1.0 +/- 0.1, respectively, in these two groups. 3. Plasma levels of brain natriuretic peptide and atrial natriuretic peptide were significantly correlated in the healthy subjects and within each group of patients. When all groups were taken together, there was an overall correlation of 0.90 (P < 0.001, n = 73).(ABSTRACT TRUNCATED AT 250 WORDS)

title: Circulating natriuretic peptide concentrations in patients with end-stage renal disease: role of brain natriuretic peptide as a biomarker for ventricular remodeling.
abstract: To determine levels of natriuretic peptides (NPs) in patients with end-stage renal disease (ESRD) and to examine the relationship of these cardiovascular peptides to left ventricular hypertrophy (LVH) and to cardiac mortality.



One hundred twelve dialysis patients without clinical evidence of congestive heart failure underwent plasma measurement of NP concentrations and echocardiographic investigation for left ventricular mass index (LVMI).



Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations correlated positively with LVMI and inversely with left ventricular ejection fraction, whereas C-type NP and Dendroaspis NP levels did not correlate with LVMI. In dialysis patients with LVH (LVMI >125 g/m2), plasma ANP and BNP concentrations were increased compared with those in dialysis patients without LVH (both P<001). In a subset of 15 dialysis patients without LVH or other concomitant diseases, plasma BNP concentrations were not significantly increased compared with those in 35 controls (mean +/- SD, 20.1+/-13.4 vs 13.5+/-9.6 pg/mL; P=.06), demonstrating that the BNP concentration was not increased by renal dysfunction alone. Furthermore, the BNP level was significantly higher in the 16 patients who died from cardiovascular causes compared with survivors (mean +/- SD, 129+/-13 vs 57+/-7 pg/mL; P<.003) and was significantly associated with greater risk of cardiovascular death in Cox regression analysis (P<.001), as was the ANP level (P=.002).



Elevation of the plasma BNP concentration is more specifically related to LVH compared with the other NP levels in patients with ESRD independent of congestive heart failure. Thus, BNP serves as an important plasma biomarker for ventricular hypertrophy in dialysis patients with ESRD.

title: Plasma levels and dialysance of atrial natriuretic peptide in terminal renal failure.
abstract: Plasma immunoreactive atrial natriuretic peptide (irANP) levels, their chromatographic profile, relationship with hemodynamic variables, and responses to hemodialysis (HD) or postural changes were investigated in HD patients. Peripheral venous supine plasma irANP averaged 167 +/- 31 (+/- SEM) pg/ml in 12 normal subjects (age 63 +/- 2 yr). In 42 HD patients (mean age 65 +/- 1 yr), plasma irANP in peripheral arterio-venous fistulae was high (447 +/- 50 pg/ml, P less than 0.01) before HD and decreased (P less than 0.001) to 164 +/- 24 pg/ml after HD. The latter reduced body weight by -2.3 +/- 0.2 kg (P less than 0.001) and blood pressure from 139/77 +/- 4/2 to 126/73 +/- 4/2 mm Hg (P less than 0.01). Pre-dialysis plasma irANP in right atrium, pulmonary artery or avfistula correlated with pulmonary capillary wedge pressure (N = 10, r = 0.66 to 0.73; P less than 0.05); HD-induced changes in these variables were also correlated (r = 0.80 to 0.90; P less than 0.05 to less than 0.01). Compared with supine values, upright posture decreased plasma irANP in 12 normal subjects and 8 HD patients (-40 and -42%, respectively, P less than 0.01). IrANP clearance from plasma averaged 24 +/- 5 ml/min across the hemodialyzer (N = 6) and 46 +/- 3 ml/min across the hemofilter (N = 4). We conclude that in terminal renal failure, circulating irANP consists largely of alpha ANP, is often elevated before HD, decreases with the change from recumbency to standing, falls after removal of excess fluid, and may depend strongly on left atrial and pulmonary arterial pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

title: Change in plasma immunoreactive atrial natriuretic peptide during sequential ultrafiltration and haemodialysis.
abstract: Plasma immunoreactive human atrial natriuretic peptide (Ir-ANP) levels were measured in eight patients with chronic renal failure who were volume-expanded and during treatment by sequential ultrafiltration and haemodialysis. One patient was studied at two separate treatment sessions. Plasma Ir-ANP levels were raised in all patients (mean +/- SE 184 +/- 44 pmol/l, n = 9) compared with healthy controls (11 +/- 1.4 pmol/l), but showed considerable inter-patient variability. Plasma Ir-ANP levels fell with fluid removal during ultrafiltration (123 +/- 30 pmol/l, n = 9, P less than 0.02) and again as fluid was removed during haemodialysis (76 +/- 20 pmol/l, n = 9, P less than 0.02). Seven patients studied 48 h later, before their next dialysis treatment, had regained weight and showed a coincident rise in circulating plasma Ir-ANP (130 +/- 33 pmol/l, n = 7). Our data would support the hypothesis that the secretion of ANP is determined by volume or by a stimulus related to volume. However, it does not exclude the possibility that a factor other than extracellular fluid volume expansion contributes to the raised plasma Ir-ANP levels in chronic renal failure.

title: Atrial natriuretic factor in renal failure and posthemodialytic postural hypotension.
abstract: Atrial natriuretic factor (ANF) levels were ten times normal in hemodialysis patients before dialysis. ANF was not cleared by the dialyzer membrane but plasma levels decreased 47% by the end of dialysis. Patients undergoing peritoneal dialysis had plasma ANF levels four times normal and had detectable ANF in their dialysate. Hemodialysis patients with a marked fall in BP after dialysis had higher ANF levels (P less than 0.05) and lower norepinephrine (NE) levels (P less than 0.05) associated with a failure to increase NE in response to dialysis. Elevated ANF levels are associated with postdialysis hypotension in hemodialysis patients.

title: The rise and fall of atrial natriuretic peptide for acute renal failure
abstract: Atrial natriuretic peptide can increase glomerular filtration rate and filtration fraction and can promote natriuresis, effects that would logically seem to improve renal function after acute tubular necrosis from ischemic or toxic injury. Early human trials suggested a beneficial effect of atrial natriuretic peptide on creatinine clearance, and a reduction in the need for dialysis in treated patients. However, randomized, placebo-controlled trials have failed to show a clinically relevant benefit on survival, dialysis-free survival, or renal function in patients treated with this agent.

title: Effects of atrial natriuretic peptide in clinical acute renal failure.
abstract: Fifty-three consenting patients meeting clinical and urine composition criteria for established intrinsic ARF were assigned to two treatment groups. Group I patients were treated with human atrial natriuretic peptide (ANP) with or without diuretics. Groups II patients were treated with or without diuretics and with no ANP. Age, sex, etiology of ARF, entry serum creatinines (SCr) (Group I, 5.3 +/- 1.8; Group II, 5.1 +/- 2.1 mg/dl) and creatinine clearances (CCr) (Group I, 9.9 +/- 2.1; Group II, 9.2 +/- 2.1 ml/min) were similar. Thirty patients received ANP [0.20 micrograms/kg/min i.v. x 24 hr (N = 20) or 0.08 micrograms/kg/min i.a. x 8 hr (N = 10)] and furosemide, 0.5 mg/kg/hr x 24 hr or mannitol, 12.5 g every six hours x 4, or no diuretic; 23 Group II patients received diuretics as above or no diuretic in a similar distribution to Group I. CCr (verified with simultaneous inulin clearances x 12, r = 0.93, P < 0.001) increased significantly by eight hours of ANP treatment to 17.1 +/- 3.2 ml/min and by 24 hours after discontinuing ANP to 21.0 +/- 4.4 ml/min (both P < 0.05). There was no corresponding increase in CCr in Group II. Dialysis was required in 23% of Group I and in 52% of Group II patients (different at P < 0.05). Mortality rates of 17% for Group I and 35% for Group II were not significantly different (P = 0.11). It is concluded that parenteral ANP increases CCr and reduces need for dialysis in patients with established intrinsic ARF.

title: Renal sympathetic nerves attenuate the natriuretic effects of atrial peptide.
abstract: Low frequencies of renal sympathetic nerve stimulation increase renal tubular sodium reabsorption without causing renal hemodynamic changes. We tested the hypothesis that the natriuretic responses to synthetic atrial peptides (atriopeptin III [APIII], 24 amino acids) are modulated by the renal tubular actions of the renal nerves. Responses to intravenous infusions of APIII (0.5 and 2.0 micrograms/kg/min) were examined in three groups of chloralose-anesthetized rats. Bilateral renal function studies were done in all three groups in which the right kidney was denervated and the left kidney was either left innervated (group I, n = 10) or the distal portion of the transected left renal nerves was stimulated at 15 V, 1 msec, and 0.5 Hz (group II, n = 8) or 1.0 Hz (group III, n = 8). In groups I, II, and III, diuretic and natriuretic responses to APIII were significantly (p less than 0.05) less in the kidneys with intact innervation or low-frequency (0.5 and 1.0 Hz) renal nerve stimulation than in the denervated kidneys. In conclusion, renal excretory responses to APIII are substantially modulated by the renal tubular actions resulting from low-frequency renal nerve stimulation. We speculate that the decrease in renal excretory responses to atrial peptides in pathophysiologic states such as congestive heart failure, nephrotic syndrome, and cirrhosis may result in part from an increase in the prevailing level of renal sympathetic nerve activity.

title: Protective effect of prostaglandin [PGE2] and in glycerol-induced acute renal failure in rats.
abstract: 1. Acute renal failure was induced in female Sprague-Dawley rats by the subcutaneous injection of glycerol. 2. Four groups of rats were studied; all animals received a glycerol challenge. Group A (control) were sham-operated only, group B received an infusion of sodium chloride solution (150 mmol/l; saline) for 24 h, group C received an infusion containing prostaglandin E2 (PGE2, 1.7 micronmol/l) in saline and group D a solution containing PGE2 (3.4 micronmol/l) in saline. 3. All rats were killed 48 h after glycerol challenge. The degree of renal impairment was assessed by serum creatinine concentration, which did not differ in sham-operated animals and the group receiving saline alone. The group of rats receiving the lower dose dose of PGE2 has a significantly lower mean serum creatinine concentration than the saline-infused control rats (P less than 0.0025). Creatinine concentration was further lowered by the higher dose of PGE2 but there was not a significant difference in the number of rats showing severe tubular necrosis histologically. 4. The study demonstrates that intravenous infusion of prostaglandin E2 has a protective influence on glycerol-induced renal failure in the rat; the protection afforded may be due to the vasodilator effect of PGE2 and/or an effect on glomerular permeability.

title: Plasma atrial natriuretic factor and graft function in renal transplant recipients.
abstract: In order to determine the relationships between allograft function and the recipient's plasma concentrations of atrial natriuretic factor (ANF), plasma ANF was measured by radioimmunoassay for 14 days after cadaveric renal transplantation in 9 patients aged 19-64 years. All received immunosuppression with prednisolone, azathioprine, and cyclosporine. No patient was in heart failure. During the study period, six grafts functioned, and three were nonfunctioning--two due to rejection and one to acute tubular necrosis. Plasma ANF concentration at the time of transplantation was 48 +/- 16 pmol/L (mean +/- SEM) range 15-145 pmol/L. In the six patients with functioning grafts, ANF declined in parallel with the fall in serum creatinine (658 +/- 35 to 210 +/- 34 mumol/L). In the three with nonfunctioning grafts, serum creatinine and plasma ANF concentration both increased. There was overall a significant linear relation between serum creatinine and plasma ANF (r = 0.527, P less than 0.001). The changes in plasma ANF after renal transplantation bore no relationship to changes in body weight or blood pressure. However, plasma ANF concentration was related to allograft fractional sodium excretion (r = 0.687, p less than 0.001). We conclude that elevated plasma ANF concentrations in end-stage renal disease are restored to normal by successful renal transplantation, implying that renal function is a determinant of plasma ANF concentration. Circulating plasma ANF may also have a direct effect on allograft sodium excretion.

title: Atrial natriuretic factor does not improve the outcome of cadaveric renal transplantation.
abstract: Atrial natriuretic factor (ANF) ameliorates renal damage in animal models of acute ischemic renal failure. Consequently, ANF could blunt acute tubular necrosis related to ischemia that occurs frequently in cadaveric renal transplants. Ten pairs of cadaveric kidneys were transplanted into 20 recipients. Paired recipients received either alpha-human ANF (hANF) or vehicle alone in a prospective, double-blind protocol. Upon revascularization of the allograft, either hANF or vehicle was administered intravenously as a 50-micrograms bolus, followed by a 4-h infusion (0.1 microgram/kg/min). Glomerular filtration rate ([125I]iothalamate clearance) was measured between 4 and 7 days posttransplant and again between 14 and 21 days posttransplant. Serum creatinine was measured daily when patients were in the hospital, then twice weekly as patients were examined in the outpatient clinic. Between the groups, there was no significant difference in age of the recipients or donors, cold ischemia time, or histocompatibility leukocyte antigen match. Infusion of hANF had no adverse effects. When subjects receiving hANF were compared with those treated with vehicle alone, there were no significant differences in serum creatinine or glomerular filtration rate. Three hANF and four vehicle recipients required dialysis postoperatively. At 1 month posttransplant, 19 of 20 patients had functioning allografts; an allograft from one hANF recipient never functioned. It was concluded that hANF, when given by the protocol of this study, had no beneficial effect on the outcome of cadaveric renal transplantation in humans.

title: In vitro and in vivo protective effect of atriopeptin III on ischemic acute renal failure.
abstract: The effect of atriopeptin III (AP-III) on ameliorate ischemic acute renal failure was first examined in the isolated perfused kidney. Isolated rat kidneys were clamped for 1 h and reperfused for 30 min without therapy and then perfused with either 0 (control) or 100 micrograms/dl AP-III. In this system AP-III significantly improved renal plasma flow (39.6 +/- 2.4 vs. 32.2 +/- 2.1 ml/min per g; P less than 0.05) inulin clearance (182.6 +/- 49.2 vs. 24.6 +/- 6.2 microliters/min per g; P less than 0.05), urine flow (52.9 +/- 12.1 vs. 7.1 +/- 0.8 microliters/min per g, P less than 0.01), and net tubular sodium reabsorption (21.2 +/- 6.6 vs. 2.9 +/- 0.9 mumol/min per g, P less than 0.05) as compared with control. A second series of in vivo studies experiments were performed using 1 h of bilateral renal artery clamping followed by an intravenous infusion of either saline alone (control) or AP-III (0.20 microgram/kg per min) for 60 min. The results demonstrated that inulin clearance (244.4 +/- 25.1 vs. 15.8 +/- 8.2 microliters/min per 100 g; P less than 0.01), urine flow (23.1 +/- 5.9 vs. 1.1 +/- 0.5 microliters/min per 100 g; P less than 0.01), and net tubular sodium reabsorption (38.9 +/- 4.7 vs. 4.3 +/- 1.6 mumol/min per 100 g; P less than 0.01) were significantly higher in AP-III-treated rats than controls during the hour of AP-III infusion. In 1 h posttreatment study this significant protective effect of AP-III was documented to persist. In more chronic studies animals treated acutely with AP-III had lower serum creatinine concentration at 24 h (1.8 +/- 0.3 vs. 3.3 +/- 0.4 mg/dl; P less than 0.01) and 48 (1.0 +/- 0.2 vs. 2.4 +/- 4.0 mg/dl; P less than 0.01) after the 60 min of ischemia than controls. Renal adenosine triphosphate regeneration as assessed by P-31 nuclear magnetic resonance during reflow was also significantly improved in AP-III-treated animals at 1 h (3.03 +/- 0.30 vs. 1.45 +/- 0.40 mumol/g dry wt; P less than 0.05) and 2 h (3.98 +/- 0.46 vs. 1.80 +/- 0.05 mumol/g dry wt; P less than 0.01) or reflow as compared with control rats. Thus, AP-III significantly ameliorates ischemic acute renal failure both in vitro and in vivo in the rat.

title: Amelioration of postischaemic acute renal failure in conscious dogs by human atrial natriuretic peptide.
abstract: We studied the effect of human ANP (alpha-hANP)-99-126 on the course of postischaemic acute renal failure in unilaterally nephrectomised, conscious dogs subjected to 120 min of renal ischaemia. In contrast to a control group A (n = 7), the investigational group B (n = 9) received an intra-aortic bolus injection of 100 micrograms/kg alpha-hANP and an additional continuous infusion of 0.3 micrograms/kg per min x 180 min immediately after ischaemia. On days 1 and 2 after ischaemia, only the bolus injection was repeated. Administration of hANP resulted in a marked restoration of GFR (29 +/- 2 vs 18 +/- 4 ml/min, P less than or equal to 0.01), diuresis (0.8 +/- 0.1 vs 0.5 +/- 0.1 ml/min, P less than or equal to 0.05), and natriuresis (44 +/- 7 vs 25 +/- 4 mumol/min, P less than or equal to 0.05) on the first postischaemic day, which was mirrored by a reduction in nitrogen retention (Purea: 8 +/- 1 vs 12 +/- 2 mmol/l P less than or equal to 0.05, Pcrea: 137 +/- 20 vs 204 +/- 37 mumol/l). Renal perfusion, however, was only slightly improved on day 1 after ischaemia (198 +/- 20 vs 163 +/- 27 ml/min, N.S.). Our data clearly demonstrate that repeated bolus applications of hANP ameliorate postischaemic acute renal failure in conscious dogs. We assume that the observed beneficial effect on GFR might be the consequence of an increase in glomerular capillary pressure rather than an improvement of renal perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

title: Atrial natriuretic peptide protects against acute ischemic renal failure in the rat.
abstract: Because of its ability to increase glomerular filtration, antagonize the actions of vasoconstrictors, and produce vasodilation, alpha human atrial natriuretic peptide (alpha-hANP) was evaluated for its potentially beneficial effects in experimental ischemic renal failure induced by 45-60 min of renal artery occlusion in bilaterally or unilaterally renally intact Sprague-Dawley rats. After ischemia, a 4-h intrarenal infusion of alpha-hANP restored 14C-inulin clearances in bilaterally and unilaterally intact animals from 0.05 +/- 0.006 and 0.05 +/- 0.01 ml/min per 100 g to 0.314 +/- 0.04 and 0.25 +/- 0.01 ml/min per 100 g, respectively (P less than 0.001, n = 8), compared with normal values of 0.49 +/- 0.023 ml/min per 100 g. Histologically, there was a progressive decrease in medullary hyperemia and prevention of intratubular cell shedding and granulocyte margination as a result of the 4-h alpha-hANP infusion such that after 24 and 48 h the histological appearance of the tissue was essentially normal. The results show that a 4-h intrarenal infusion of alpha-hANP after renal ischemia can preserve glomerular filtration rate and reduce renal tissue damage.

title: Therapeutic use of the natriuretic peptide ularitide in acute renal failure.
abstract: Ularitide is a member of the natriuretic peptide family. This hormone exhibits an N-terminal extension by four amino acids compared with atrial natriuretic peptide. Ularitide was shown to exert strong diuretic and natriuretic effects when infused intravenously. Its main action sites are the glomerulum, inducing preglomerular vasodilation and postglomerular vasoconstriction and thereby elevating the glomerular filtration rate, and the tubular system inhibiting Na(+)-reabsorption. In initial uncontrolled clinical trials, this peptide was shown to have beneficial effects in patients suffering from oliguric acute renal failure.



We conducted a double-blind, placebo-controlled, multicenter, dose-finding trial recruiting 176 patients randomized into 4 different Ularitide doses groups (U5, U20, U40, and U80 ng/kg/min) and a placebo group (U0). Ularitide/placebo infusion was performed for 5 days with half the originally infused dose on day 5. The primary objective of the study was to test various doses of Ularitide in patients suffering from oliguric acute renal failure to avoid mechanical renal replacement therapy during the first 12 hours.



The results indicate that Ularitide does not reduce the incidence of mechanical renal replacement therapy compared with placebo-treated patients during the first 12 h of treatment (U0: 36 (20), U5: 35 (11), U20: 36 (9), U40: 28 (8), U80: 41 (12), (% (n) (p = 0.87)). Diuresis increased in the Ularitide-treated groups and the placebo group after onset of infusion and did not show any significant difference in the first 12 h collection period (U0: 576, U5: 514, U20: 500, U40: 360, U80: 158 ML/12h (Median), (p = 0.16)).



In summary, the incidence of mechanical renal replacement therapy in critically ill patients suffering from oliguric acute renal failure could not be altered positively by Ularitide administration according to our protocol. Further prospective clinical trials are needed to answer the question whether a different patient collective or a prophylactic administration of Ularitide are more promising approaches in the clinical setting of oliguric acute renal failure.

title: Toxic acute renal failure in the rat: effects of diltiazem and urodilatin on renal function.
abstract: Beneficial effects of natriuretic peptides have been reported in different models of acute renal failure (ARF). Calcium antagonists can also improve renal function, especially in ischemic models of ARF. The aim of our study was to investigate the effects of urodilatin and diltiazem alone and in combination in uranyl nitrate-induced toxic ARF in the rat. Three hours after induction of ARF glomerular filtration rate (GFR) was clearly diminished to about 50% compared to basal values. Intravenous infusion of diltiazem and urodilatin revealed a significant increase of GFR that even continued after cessation of drug delivery. Combined administration of urodilatin and diltiazem had no additional effect, probably due to a more pronounced fall in blood pressure in this group. Besides their vasorelaxing and blood pressure lowering effects both drugs also revealed diuretic activity. In conclusion both urodilatin and diltiazem are able to elevate GFR in the early phase of toxic ARF in the rat.

title: Urodilatin, not nitroprusside, combined with dopamine reverses ischemic acute renal failure.
abstract: The present study was undertaken to: (a) clarify the comparative renal potency of bolus injection of the natriuretic peptides urodilatin and ANF99-126 in the rat; (b) establish whether or not intravenous (i.v.) infusion of urodilatin (200 ng/min) combined with dopamine (UD) to maintain mean arterial pressure could improve GFR or renal histology in established experimental ischemic acute renal failure (ARF) induced by 30 minutes of bilateral renal artery clamping; (c) assess comparative efficacies of nitroprusside, an activator of soluble guanylate cyclase, combined with dopamine (ND) or control infusions of dopamine alone (DA), under equivalent conditions; and (d) determine effects of intra-renal arterial infusions of the stable cGMP analogue dibutyryl-cGMP immediately after renal artery clamping (RAC). After initial dose finding studies, i.v. infusion of UD 24 hours after 30 minutes of RAC improved GFR over five hours from 0.24 +/- 0.04 to 1.0 +/- 0.16 ml/min in association with a threefold rise in plasma cGMP and a 13-fold increase in urinary cGMP excretion. Plasma creatinine dropped by 41% from 230 +/- 16 to 135 +/- 18 microM/liter and was still reduced 24 hours later with values averaging 106 +/- 14 compared to 274 +/- 53 microM/liter in non-treated animals. During infusion, UV and FENa+ increased from 1.4 +/- 0.2 to 8.3 ml/min, and from 2.9 +/- 0.5 to maximum values of 15.8 +/- 2.4%. ND or DA alone were less effective, increasing GFR only to 14 and 20%, respectively, of normal values, but improvements were not sustained; in contrast to UD, ND did not alter plasma or urinary cGMP. In addition, DBcGMP was ineffective in improving GFR during early ARF. Histologically UD, but not ND, markedly reduced the incidence of granular casts, tubular desquamation and tubular necrosis in cortical areas and increased the incidence of medullary mitoses.

title: Anaritide in Acute Tubular Necrosis
abstract: Atrial natriuretic peptide, a hormone synthesized by the cardiac atria, increases the glomerular filtration rate by dilating afferent arterioles while constricting efferent arterioles. It has been shown to improve glomerular filtration, urinary output, and renal histopathology in laboratory animals with acute renal dysfunction. Anaritide is a 25-amino-acid synthetic form of atrial natriuretic peptide.  We conducted a multicenter, randomized, double-blind, placebo-controlled clinical trial of anaritide in 504 critically ill patients with acute tubular necrosis. The patients received a 24-hour intravenous infusion of either anaritide (0.2 microgram per kilogram of body weight per minute) or placebo. The primary end point was dialysis-free survival for 21 days after treatment. Other end points included the need for dialysis, changes in the serum creatinine concentration, and mortality.  The rate of dialysis-free survival was 47 percent in the placebo group and 43 percent in the anaritide group (P = 0.35). In the prospectively defined subgroup of 120 patients with oliguria (urinary output, < 400 ml per day), dialysis-free survival was 8 percent in the placebo group (5 of 60 patients) and 27 percent in the anaritide group (16 of 60 patients, P = 0.008). Anaritide-treated patients with oliguria who no longer had oliguria after treatment benefited the most. Conversely, among the 378 patients without oliguria, dialysis-free survival was 59 percent in the placebo group (116 of 195 patients) and 48 percent in the anaritide group (88 of 183 patients, P = 0.03).  The administration of anaritide did not improve the overall rate of dialysis-free survival in critically ill patients with acute tubular necrosis. However, anaritide may improve dialysis-free survival in patients with oliguria and may worsen it in patients without oliguria who have acute tubular necrosis.

title: Severe hypotension and bradycardia after continuous intravenous infusion of urodilatin (ANP 95–126) in a patient with congestive heart failure
abstract: The effects of a continuous i.v. infusion of urodilatin at a dose of 30 ng kg‐1 min‐1 were studied in a patient with congestive heart failure. After 30 min, urodilatin had induced a marked stimulation of plasma cyclic GMP concentrations. In parallel haematocrit increased. No significant diuresis and no change of invasive haemodynamics was observed. After 2 h the patient developed a profuse perspiration. Eighty minutes later he suffered from dizziness due to hypotension (blood pressure 80/40 mmHg) and a sudden bradycardia (50bpm). Urodilatin was discontinued and symtoms were relieved by bed tilt and rapid infusion of isotonic saline solution. Mechanisms contributing to these adverse effects may be fluid extravasation to the third space and sympathoinhibitory effects known to occur with natriuretic peptide infusion.

title: Prospective study of atrial natriuretic peptide for the prevention of radiocontrast-induced nephropathy.
abstract: Radiocontrast-induced nephropathy (RCIN) is a common cause of hospital-acquired acute renal failure and is associated with a high mortality rate. RCIN is potentially preventable, because administration of the radiocontrast agent is predictable, and a high-risk population has been identified. This multicenter, prospective, randomized, double-blind, placebo-controlled trial was performed to evaluate the efficacy of intravenous atrial natriuretic peptide (anaritide, ANP 4-28) to prevent RCIN. Patients with stable chronic renal failure (serum creatinine greater than 1.8 mg/dL or serum creatinine between 1.5 and 1.8 mg/dL with estimated creatinine clearance of < or = 65 mL/min) were assigned to receive either placebo or one of three doses of anaritide (0.01 microg/kg/min, 0.05 microg/kg/min, or 0.1 microg/kg/min) for 30 minutes before and continuing for 30 minutes after radiocontrast administration. All patients were given intravenous 0.45% saline for 12 hours before the radiocontrast procedure and continuing for 12 hours after the last dose of radiocontrast. Both ionic and nonionic radiocontrast agents were administered. RCIN was defined as either an absolute increase of serum creatinine of > or = 0.5 mg/dL or a percent increase of > or = 25% over baseline. Of the 247 patients who completed the study, 50% had diabetes mellitus. There were no statistical differences in baseline serum creatinine, change in serum creatinine, or the incidence of RCIN. The incidence of RCIN was placebo, 19%; anaritide (0.01), 23%; anaritide (0.05), 23%; anaritide (0.1), 25%. Patients with diabetes mellitus had a significantly greater incidence of RCIN: placebo, 26% versus 9%; anaritide (0.01), 33% versus 13%; anaritide (0.05), 26% versus 21%; anaritide (0.1), 39% versus 8% (diabetic v nondiabetic, P < 0.002). There was no effect in the diabetic or nondiabetic groups by anaritide on the incidence of RCIN. Comparison of the highest-risk group of patients, defined as patients with diabetes mellitus and a baseline serum creatinine > or = 1.8 mg/dL, with the lowest-risk group, defined as patients without diabetes mellitus and a baseline serum creatinine of 1.8 mg/dL or less, did not show a beneficial effect of anaritide administration. In conclusion, administration of intravenous anaritide before and during a radiocontrast study did not reduce the incidence of RCIN in patients with preexisting chronic renal failure, with or without diabetes mellitus.

title: Mechanism of ischemia-enhanced aminoglycoside binding and uptake by proximal tubule cells.
abstract: Preceding ischemia or concurrent hypotension is known to enhance aminoglycoside nephrotoxicity; however, the underlying mechanisms responsible have not been determined. To investigate the effect of preceding mild ischemia on cellular gentamicin handling, brush-border membrane vesicle binding and in vivo cellular gentamicin uptake were quantified using [3H]gentamicin as a tracer. Fifteen minutes of ischemia resulted in a marked increase in apical membrane gentamicin binding (2.8 +/- 0.4 vs. 4.9 +/- 0.8 nmol/mg protein, P < 0.01). This increase was associated with an increased number of binding sites (3.7 +/- 0.3 vs. 9.1 +/- 2.3 nmol/mg protein, P < 0.01) and a reduced binding affinity (11.8 +/- 2.2 vs. 27.7 +/- 10.4 microM, P < 0.01). This increase in gentamicin binding was accompanied by alterations in apical membrane phospholipids including a doubling of phosphatidylinositol (PI) levels (13.8 +/- 0.4 vs. 27.5 +/- 3.1 nmol/mg protein, P < 0.01). Furthermore, treatment of apical membrane vesicles with PI-specific phospholipase C markedly reduced the difference in gentamicin binding between paired control and ischemic membrane fractions. Increased gentamicin binding was associated with increased in vivo uptake of gentamicin by S1/S2 and S3 cells. Outer cortical uptake of gentamicin increased from 2.18 +/- 0.39 to 2.68 +/- 0.27 nmol/mg protein (P < 0.01) after 15 min of ischemia and 4 h of reperfusion. Juxtamedullary uptake also increased from 1.39 +/- 0.31 to 1.75 +/- 0.12 nmol/mg protein (P < 0.01). Immunocytochemical techniques, utilizing immunogold labeling, showed gentamicin was taken up via the receptor-mediated endocytic pathway by S1/S2 and S3 cells. After ischemic injury gentamicin was localized in abnormal intracellular accumulations in S3 but not S1 or S2 cells. Taken together, these data indicate ischemia results in a marked increase in apical gentamicin binding due to increases in apical PI content. This is associated with increased internalization by S1/S2 and S3 cells and abnormal intracellular compartmentalization of gentamicin within S3 cells.

title: Nitric oxide and prostanoids protect the renal outer medulla from radiocontrast toxicity in the rat.
abstract: Human radiocontrast nephrotoxicity is predicted by the presence of multiple risk factors, often associated with compromised renal circulation. To produce a simple model of radiocontrast nephropathy, rats were pretreated with indomethacin and N omega-nitro-L-arginine methyl ester (L-NAME, to inhibit nitric oxide synthesis) before the administration of iothalamate. Acute renal failure consistently developed, with a decline in creatinine clearance from 1.05 +/- 0.10 to 0.27 +/- 0.05 ml/min (P < 0.001) associated with selective necrosis of 49 +/- 9% of medullary thick ascending limbs. Hemodynamic studies using laser-Doppler probes revealed that when injected alone, iothalamate increased outer medullary blood flow to 196 +/- 25% of baseline (P < 0.001). Pretreatment by L-NAME or indomethacin both reduced basal medullary blood flow and transformed the medullary vasodilator response to radiocontrast into vasoconstriction, with a prolonged reduction of medullary blood flow to less then half of baseline. Combined administration of indomethacin, L-NAME, and iothalamate lowered medullary blood flow to 12 +/- 4% of baseline. We conclude that prostanoids and nitric oxide have an important protective role in the renal response to radiocontrast material. Reduced synthesis of these vasoactive substances in renal/vascular diseases may predispose patients to radiocontrast nephropathy.

title: Vasodilator prostaglandins (PG) prevent renal damage after ischemia.
abstract: Thromboxane (Tx) synthase but not cyclo-oxygenase inhibitors prevent acute tubular necrosis (ATN) after renal ischemia, a phenomenon believed to be due to stimulation of the endogenous production of vasodilating prostaglandins (PG). This study directly tests that vasodilating PG protect against the consequences of renal ischemia. Anesthetized, 500-g rats had right nephrectomy and 45 minutes of left renal pedicle clamping or sham clamping. The rats were treated with intravenous (I.V.) saline 1.9 mL/h starting 40 minutes after clamping or sham clamping. All rats except the sham group (N = 8) were pretreated 1 hour before ischemia with ibuprofen (12 mg/kg) to prevent prostanoid synthesis. Beginning 5 minutes before clamp release, the rats were treated intravenously for 2 hours with: saline vehicle (N = 9), PGE1 400 ng/kg/min (N = 6), nitroprusside 4 micrograms/kg/min (N = 8), or dopamine 3 micrograms/kg/min (N = 11). After 24 hours, sham rat creatinine level was 0.5 mg/dL and weight of the left kidney was 86.5% of the previously removed right kidney. Compared with sham rats, ischemia and saline treatment resulted in a rise in creatinine level to 2.7 mg/dL (p less than 0.05) and a rise in kidney weight to 101.9% (p less than 0.05); PGE1 led to a creatinine level of 1.1 mg/dL, a value lower than that of the rats treated with saline (p less than 0.05), and a kidney weight of 92.0%, a value similar to that of sham rats; nitroprusside and dopamine led to a rise in creatinine levels to 3.2 mg/dL (p less than 0.05) and 2.3 mg/dL (p less than 0.05), respectively, as well as a rise in kidney weight to 108.0% (p less than 0.05) and 105.4% (p less than 0.05), respectively. Histologic examination showed ATN in rats treated with saline, nitroprusside, and dopamine, but not in rats treated with PGE1. These results indicate that PGE1 protects the cyclo-oxygenase-treated kidney against ischemia-induced ATN.

title: Acute oliguric renal failure induced by indomethacin: possible mechanism.
abstract: A patient with compensated congestive heart failure suffered acute deterioration of her renal function and cardiac status, requiring peritoneal dialysis, in association with indomethacin therapy. Discontinuation of this inhibitor of prostaglandin synthesis led to a prompt improvement in both her renal function and cardiac status. The patient was rechallenged with indomethacin and again developed acute reduction of her glomerular filtration rate and severe volume retention, which were again totally reversed when the drug was stopped. Urinary prostaglandin E was measured by radioimmunoassay in this patient and five additional patients with congestive heart failure and prerenal azotemia. All patients were found to have elevated levels of urinary prostaglandin E. The possible role for renal prostaglandin E as a compensatory mechanism to the vasoconstrictive stimuli present in congestive heart failure is discussed. The potential danger of inhibitors of prostaglandin synthesis in patients with congestive heart failure and prerenal azotemia is emphasized.

title: Diuresis and improved renal hemodynamics produced by prostaglandin E1 in the dog with norepinephrine-induced acute renal failure.
abstract: Unilateral acute renal failure was induced in dogs by renal artery infusion of norepinephrine. Renal hemodynamics and function were studied before and 5 days after norepinephrine infusion, and during subsequent renal artery infusion of prostaglandin E1. After norepinephrine, the infused kidney exhibited decreased urine volume, sodium excretion, and creatinine clearance. Cortical blood flow, determined with radioactive microspheres, also decreased. No redistribution of intracortical blood flow occurred. Arteriographically, proximal vessels were constricted and the cortical nephrogram density diminished. During prostaglandin E1 infusion, urine volume, sodium excretion, and cortical blood flow increased. Creatinine clearance did not change significantly. Blood flow was redistributed from the outer third to the inner third of the cortex. Proximal vessels were dilated and the cortical nephrogram density was enhanced. The apparent dissociation of cortical blood flow from creatinine clearance suggests that prostaglandin E1-induced diuresis and natriuresis result from a mechanism other than increased glomerular filtration.