Cloning and sequence analysis of cDNA encoding a precursor for human atrial natriuretic polypeptide

Gene for the rat atrial natriuretic peptide is regulated by glucocorticoids in vitro

Glucocorticoids regulate the expression of the gene for atrial natriuretic peptide (ANP) in neonatal cardiocytes. Dexamethasone (Dex) increased cytoplasmic ANP mRNA levels and media ANP immunoreactivity in a dose-dependent fashion. These effects were not shared by the other classes of steroid hormones and were reversed by the glucocorticoid antagonist RU 38486. The effect on ANP mRNA levels resulted, at least in part, from enhanced transcription of the gene. Dex effected a two-fold increase in ANP gene activity assessed using a run-on transcription assay. The turnover of the ANP transcript was approximated using a standard pulse-chase technique. The half-life of the ANP mRNA was 18 h in hormone-free media. In the presence of Dex this half-life increased modestly to 30 h, although the increase relative to the control did not reach statistical significance. The effect of Dex at the level of the individual myocardial cell was assessed by in situ hybridization analysis using a specific [3H]cRNA probe. These studies demonstrated a significant level of ANP expression within a subpopulation of cells in the cultures. Exposure of the cells to Dex for 24 h did not recruit additional cells into the expressing pool (27.3% cells/high power field vs. 31.3% for the control) but did increase the level of expression (i.e., grain density) within individual cells. These findings indicate that glucocorticoids stimulate expression of the ANP gene directly at the level of the myocardial cell. This results predominantly from transcriptional activation in cells already expressing the gene rather than through recruitment of previously quiescent cells.

Expression of atrial natriuretic factor as a cleavable fusion protein with chloramphenicol acetyltransferase in Escherichia coli

Recombinant fusion proteins containing human atrial natriuretic factor, ANF(1-28) joined to chloramphenicol acetyltransferase (CAT) via cleavable linker sequences have been produced in Escherichia coli. The linker sequences were designed to allow the release of authentic ANF(1-28) following proteolytic cleavage by enterokinase or thrombin, or chemical cleavage with 2-(2-nitrophenylsulphenyl)-3-methyl-3'-bromoindolenine. Proteins, containing ANF(1-28) fused to the carboxyl-terminal region of CAT (using the ScaI restriction site in the cat gene), were largely soluble in E. coli and were obtained in higher yield than analogues containing ANF(1-28) linked to shorter CAT sequences. The longer derivatives also retained CAT activity allowing subsequent purification by affinity chromatography.

Atrial natriuretic factor-responding and cyclic guanosine monophosphate (cGMP)-producing cells in the rat hippocampus: a combined micropharmacological and immunocytochemical approach

Atrial natriuretic factor (ANF)-responding, cyclic guanosine monophosphate (cGMP)-producing cells were visualized in the hippocampus of the rat applying cGMP immunocytochemistry to hippocampal tissue slices incubated in vitro. These cells were found scattered throughout the hippocampus with their highest density in the hilus fascia dentata. Staining with an antibody against glial fibrillary acidic protein showed a completely different pattern, suggesting a non-glial nature of the ANF-responding cells. cGMP accumulation assayed biochemically was observed already at 10 microM ANF and was sensitive to inhibition by Methylene blue. The immunocytochemical data were fully supported by the biochemical measurements of cGMP under these conditions. Our results show for the first time a response to ANF of individual, cGMP-producing cells in the CNS of the rat.

Plasma atrial natriuretic polypeptide concentrations during and after reversion of paroxysmal supraventricular tachycardias

Plasma concentrations of immunoreactive atrial natriuretic polypeptide were raised in 22 of 23 patients with paroxysmal supraventricular tachycardia and in all seven patients with atrial flutter. Plasma concentrations of atrial natriuretic polypeptide rose soon after the onset of supraventricular tachycardia. A sample taken 30 minutes after reversion to sinus rhythm (pharmacological or non-pharmacological) showed a significant fall in 19 of the 23 patients with paroxysmal supraventricular tachycardia and all seven patients with atrial flutter. Because atrial natriuretic polypeptide has powerful natriuretic and diuretic properties, an increase may contribute considerably to the polyuria that is often associated with episodes of supraventricular tachycardia.

Differential expression of carcinoembryonic antigen and nonspecific crossreacting antigen genes in human colon adenocarcinomas and normal colon mucosa

The level of mRNA for carcinoembryonic antigen (CEA) and nonspecific crossreacting antigen (NCA) in human colon adenocarcinomas and normal colon mucosa was analyzed by Northern blot hybridization using as probes 32P-labeled CEA cDNA and synthetic oligodeoxyribonucleotides specific to CEA and NCA mRNA sequences. The major 3.5-kb mRNA and a minor 4.2-kb mRNA are shown to be CEA-specific and expressed in both tissues, albeit at slightly different degrees, suggesting that the expression of CEA is regulated posttranscriptionally. Another minor mRNA of 2.9 kb is NCA-specific and expressed predominantly in cancerous tissues, suggesting its usefulness as a marker for colon cancer.

A new natriuretic peptide in porcine brain

Atrial natriuretic peptide (ANP), a hormone secreted from mammalian atria, regulates the homoeostatic balance of body fluid and blood pressure. ANP-like immunoreactivity is also present in the brain, suggesting that the peptide functions as a neuropeptide. 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 ANP, 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.

Atrial natriuretic factor-SV40 T antigen transgenes produce tumors and cardiac arrhythmias in mice

Transgenic mice that carry fusions between the transcriptional regulatory sequences of atrial natriuretic factor (a hormone intimately involved in the regulation of blood pressure) and those encoding SV40 T antigen (an oncoprotein) were generated. Although both atria express the fusion gene, the pathological response to T antigen is asymmetrical. The right atrium undergoes a several hundredfold increase in mass while the left atrium remains relatively normal in size. Hyperplasia is accompanied by a progressive increase in both the frequency and severity of abnormalities in the atrial conduction system, which ultimately result in death.

Primary structure of nonspecific crossreacting antigen (NCA), a member of carcinoembryonic antigen (CEA) gene family, deduced from cDNA sequence

A cDNA containing the entire coding region for a member of carcinoembryonic antigen (CEA) gene family has been cloned from cDNA library of HLC-1 cells by immunochemical screening with the antibody specific to nonspecific crossreacting antigen (NCA). The cDNA encodes a precursor form of a polypeptide consisting of a 34-residue signal sequence, a 108-residue N-terminal (N-) domain, a 178-residue domain (NCA-I domain) and a 24-residue domain rich in hydrophobic amino acids (M-domain). Each domain has a distinct but homologous amino acid sequence to that of the corresponding domain of CEA. Unlike the coding sequences, the 3'-untranslated sequences differ markedly in the NCA and CEA cDNAs facilitating the preparation of probes that will discriminate between nucleotide sequences for CEA and NCA.

Renal response to atrial natriuretic peptide in patients with advanced liver cirrhosis

Sodium retention in liver cirrhosis is thought to be due to, among other things, lack of a natriuretic factor or failure to respond to one. alpha-Human-atrial natriuretic peptide is a peptide that accounts partly or entirely for the circulating natriuretic activity in man. In the present study, we have evaluated the effects of the bolus administration of synthetic alpha-human-atrial natriuretic peptide (1 microgram per kg) to patients with liver cirrhosis and variable degrees of sodium retention. alpha-Human-atrial natriuretic peptide induced rapid and marked increases of diuresis and natriuresis in patients without sodium retention or with moderate retention. The results were comparable to those obtained in six healthy control subjects. Conversely, the diuretic and natriuretic effects of alpha-human-atrial natriuretic peptide were attenuated or completely blunted in patients with avid sodium retention. The two groups of patients differed not only in basal sodium excretion, but also in plasma renin activity and in plasma aldosterone levels, suggesting that the reduced responsiveness to atrial natriuretic peptide might be due to excessive antagonism by antinatriuretic factors. The direct relationship between baseline sodium excretion rate and that stimulated by human-atrial natriuretic peptide administration was consistent with this interpretation. In none of the subjects did plasma renin activity peptide and cortisol levels change after human-atrial natriuretic peptide, while plasma aldosterone slightly declined in cirrhotics. Blood pressure fell after the administration of the peptide, with the drug greater in cirrhotic than in normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of specific binding of atrial natriuretic peptide (ANP) to rat PC12 phaeochromocytoma cells

Specific binding sites for atrial natriuretic peptide have been identified in membrane of the phaeochromocytoma cell line PC12. Scatchard analysis of binding studies revealed a Kd of 794 pM and a density (Bmax) of 254 fmol/mg protein. Hormones unrelated to ANP such as angiotensin II, bradykinin and arginine-8-vasopressin did not complete for the binding sites. Of the ANP-related peptides which competed for the binding sites, the following order of affinity was established; rANP (8-33) greater than rANP (28 amino acid) greater than rat atrial peptide fragment (13-28) greater than a-hANP (28 amino acid) greater than atrial peptide fragment (1-11) greater than atriopeptin I.

Atrial natriuretic peptide: blood levels in human disease and their measurement

The atrial hormonal system consists of 126 amino acid-containing prohormone (proANP) stored in the secretory granules of atrial myocytes and 28 amino acid-containing hormone (ANP) that is secreted into the bloodstream in response to raised atrial pressure. ANP participates in the homeostasis of body fluid volume through its main receptor-mediated effects; natriuresis, inhibition of renin and aldosterone secretion, and vasodilation. It counteracts the renin-angiotensin system with the putative primary role of regulating the circulating blood volume. Although in man, the physiologic volume stimuli lead to relatively modest increases of ANP secretion, its plasma level undergoes striking changes in pathology. Marked elevations in conditions accompanied by fluid retention, most conspicuously in heart failure and renal failure, have been explained as a compensatory reaction to volume overload. The recent data suggest a decreased target organ responsiveness as one of the causes of a relative inefficiency of the high circulating levels of ANP in inducing an appropriate natriuresis in these volume overload conditions. The well established radioimmunoassay and the more recent methods of plasma ANP measurement are reviewed, and the authors' results with a commercial RIA are presented.

Atrial natriuretic peptide and vasopressin in human plasma

Using a specific radioimmunoassay for atrial natriuretic peptide (ANP), plasma immunoreactive ANP was measured in 17 normal subjects and 83 patients with various diseases. Plasma ANP concentration in normal subjects was 14.1 +/- 1.7 pg/ml (mean +/- S.E.). Relatively high plasma ANP concentrations were detected in patients with diabetes mellitus, hyperthyroidism, atrial fibrillation and liver cirrhosis. Plasma ANP concentrations in the patients correlated positively with mean arterial blood pressure and plasma AVP concentrations. Plasma ANP concentrations in the patients also had positive correlations with left atrial dimension and left ventricular diastolic dimension determined by echocardiography. Another positive correlation was observed in the patients between plasma AVP concentrations and mean arterial blood pressure. These results suggest that ANP is a volume regulatory hormone but also that ANP may be involved in the blood pressure regulating system.

Ventricular atrial natriuretic factor in the cardiomyopathic hamster model of congestive heart failure

Cardiac atria are thought to be the principle source of plasma atrial natriuretic factor (ANF), a potent natriuretic and diuretic peptide. Whether other ANF production sites are recruited in disease states exhibiting elevated plasma ANF levels is not known. Accordingly, in the cardiomyopathic hamster, an animal model of congestive heart failure with high circulating levels of ANF, contribution of ventricular tissue to total cardiac ANF production and storage was investigated. Measurements were made of immunoreactive ANF in plasma and in atrial and ventricular extracts as well as ANF mRNA levels in the atria and ventricles from normal and cardiomyopathic golden Syrian hamsters. Plasma ANF levels were higher in cardiomyopathic than in control animals. The atrial concentration of ANF (per milligram atrial weight) was 50% and 83% lower in moderate and severe congestive heart failure, respectively, when compared with controls, while atrial ANF mRNA content of cardiomyopathic hamsters was not significantly different from normal hamsters. The ventricular concentration of ANF was 3 times and 7 times higher in animals in moderate and severe heart failure when compared with controls. In severe heart failure, ventricular ANF accounted for 23% of total cardiac stores of ANF. Ventricular ANF mRNA levels were 7 times and 13 times higher in hamsters in moderate and severe heart failure as compared with control animals. Therefore, significant increases in both ANF content and ANF mRNA in ventricles of hamsters in moderate to severe heart failure suggest that the ventricle could be an important source of ANF in congestive heart failure.

Protective effect of alpha-human atrial natriuretic polypeptide (alpha-hANP) on chemical-induced pulmonary edema

It has been established that alpha-hANP, the newly discovered peptide extracted from human cardiac atria, has potent natriuretic and hypotensive actions. Our present investigation is the first to demonstrate that alpha-hANP is capable of protecting against pulmonary edema caused by various chemicals, using isolated perfused guinea pig lung system. Lungs were perfused via pulmonary artery with Krebs-Ringer bicarbonate buffer at 5.0 ml/min, and wet weight of lungs and perfusion pressure of pulmonary artery (Pa) were monitored. Bolus injection of Triton-X or CHAPS into cannulated pulmonary artery produced edema as indicated by a massive increase in wet weight and a slight increase in Pa. Constant infusion of alpha-hANP through pulmonary artery at 200 ng/ml was effective in causing decrease in wet weight of lung. Perfusion of lung with paraquat or PGF2 alpha, and repeated bolus injection of arachidonic acid or PGE2 caused elevation in both wet weight of lung and Pa. The treatment with alpha-hANP similar to that described above also protected against edema caused by paraquat or arachidonic acid. Bolus administration of epinephrine induced a slight increase in wet weight and Pa, and alpha-hANP was effective in decreasing the elevated lung wet weight and Pa of lungs. Infusion or bolus administration of alpha-hANP into control lungs increased cGMP level in outflow perfusate as well as in lung tissue significantly. In lungs with edema which were induced by Triton-X or paraquat, there was a slight increase in cGMP level in Triton-X treated and no increase in paraquat treated lung tissues. In either cases, was there any increase in cGMP level in perfusate. The specific binding study of [125I]alpha-hANP revealed that the lack of increase in cGMP was not due to a loss of receptor in Triton-X or paraquat treated lungs. Thus our study demonstrated that alpha-hANP had a direct anti-edematic action(s) in lung which was not secondary to the systemic natriuretic and/or hypotensive action(s).

Identification of alpha atrial natriuretic peptide [4-28] and [5-28] in porcine brain

Although atrial natriuretic peptide (ANP) has recently been verified to function as a neuropeptide in the central nervous system, its definite identification has not been done so far. We have isolated two ANP-related peptides from porcine brain by utilizing alpha-ANP specific radiommunoassay coupled with immunoaffinity chromatography and reverse phase HPLC. By structural analyses, these two peptides were determined to be alpha-ANP [4-28] and alpha-ANP [5-28]. They were found to elicit chick rectum relaxant activity comparable to alpha-ANP. These results indicate that proteolytic processing of ANP precursor in the central nervous system takes place in a manner different from that in heart and plasma, where gamma-ANP and alpha-ANP are known to be the main components of ANP, respectively.

Central venous pressure--a physiological stimulus for secretion of atrial natriuretic peptide in humans?

A sensitive radio-immunoassay (RIA) for the measurement of human alpha-atrial natriuretic peptide (ANP) in extracted plasma was developed and used in a study of the possible effect of posture on the concentration of ANP in plasma. The least detectable quantity was less than 2 pg per tube equivalent to 5 pg ml-1 plasma. In the middle sensitivity range (approximately 50 pg per tube), the within-assay and between-assay coefficients of variation were 4.0 and 2.8%, respectively. The recovery of ANP added to plasma prior to extraction was 95-101%. High pressure liquid chromatography (HPLC) of plasma extracts revealed that endogenous ANP was eluted in the same fractions as synthetic ANP. In order to investigate the effect of posture on the concentration of ANP in plasma six healthy volunteers were exposed to five positions in the following sequence: supine, standing, sitting, supine and 10 degrees head-down tilt on a tilt-table. The concentration of ANP was lower in the standing and sitting position than in the supine and head-down tilted position. In another study six healthy volunteers were subjected to passive tilting on a tilt-table in order to evaluate the effect of tilting on blood pressure (BP), heart rate, central venous pressure (CVP) and the concentration of ANP in plasma. It was found that a fall in CVP was accompanied by a significant decrease in the concentration of ANP and that a rise in CVP was accompanied by a rapid increase in the concentration of ANP in plasma. The results are in agreement with the hypothesis that CVP is a physiological stimulus for the secretion of ANP.

Localization of atrial natriuretic peptide mRNA and immunoreactivity in the rat heart and human atrial appendage

The localization of mRNA encoding preproatrial natriuretic peptide was investigated in tissue sections and cultures of rat heart and in sections of human right atrial appendage using the technique of in situ hybridization with 32P- and 35S-labeled RNA probes. Rat atrial natriuretic peptide (ANP) transcripts were demonstrated in numerous atrial myocytes and, to a lesser extent, in ventricular myocytes in both tissue sections and newborn rat heart cultures. These findings are consistent with those obtained by RNA blot analysis of rat heart total RNA, indicating that a single prepro-ANP transcript of approximately 900 nucleotides was present in the ventricles as well as the atria. Using a 35S-labeled RNA probe for human ANP mRNA, ANP transcripts were also localized to the majority of myocytes in the human right atrial appendage. Only background levels of autoradiographic labeling were obtained when RNA probes identical to the coding sequence of rat or human ANP mRNA were used. A close correlation was found between the distribution of ANP immunoreactivity and prepro-ANP mRNA in these preparations. These results provide unequivocal evidence for the expression of the ANP gene in the rat ventricles, as well as the atria, because myocytes in these tissues have been established as the sites of both ANP localization and precursor biosynthesis. The combined use of cardiac cultures and in situ hybridization may be of value in future studies investigating the regulation of ANP synthesis in cardiac myocytes.

Presence of atrial natriuretic polypeptide in the pulmonary vein and vena cava

Striated muscle cells and storage granules observed in the atria were found in main branches of the pulmonary veins and superior and inferior venae cavae of the rat, pig, and ox. The presence of atrial natriuretic polypeptide (ANP) in these veins was examined by reverse-phase high-performance liquid chromatography coupled with a radioimmunoassay for ANP. The veins contained 0.6 to 8.0 ng ANP/mg wet tissue with the major molecular form being gamma-ANP. ANP was detected in the peripheral lung tissue in a small quantity, but was not detected in the pulmonary artery. The identification of gamma-ANP and storage granules stained with an anti-ANP antiserum in the pulmonary vein and vena cava suggest that the veins may participate in regulating volume status, blood pressure, and cardiovascular homeostasis through the release of ANP.

Binding of synthetic beta-human atrial natriuretic peptide to cultured rat vascular smooth muscle cells

We have studied the effects of synthetic beta-human atrial natriuretic peptide (beta-hANP), an antiparallel dimer of alpha-hANP, on receptor binding and cGMP generation in cultured rat vascular smooth muscle cells and compared the effects with those of alpha-hANP. Characteristics of temperature-dependent binding and degradation of 125I-beta-hANP were similar to those of 125I-alpha-hANP. Scatchard analysis indicated a single class of binding sites for beta-hANP with a maximal binding capacity one-half that of alpha-hANP. Parallel and antiparallel dimers were equipotent in inhibiting the binding and stimulating intracellular cGMP formation, of which the maximal effect was about one-half that of alpha-hANP. Reverse-phase high performance liquid chromatography revealed that most of beta-hANP added to cells was converted to a small molecular mass component corresponding to alpha-hANP after incubation. These data suggest that the less potent effect of beta-hANP in receptor binding and cGMP generation may be partly accounted for by the possible conversion of beta-hANP to alpha-hANP at the site of target cells.

The use of a monoclonal antibody for the determination of atrial natriuretic peptides in human plasma

A monoclonal antibody (mab) directed against alpha-human atrial natriuretic peptides (alpha-hANP) was produced. Using this mab a radioimmunoassay for the determination of hANP-like immunoreactivity in human plasma was established. To demonstrate the possible application of this radioimmunoassay for clinical diagnosis, plasma levels were measured in healthy subjects and in patients with renal failure before and after hemofiltration or hemodialysis. Plasma levels in healthy subjects ranged between less than 30 and 124 pg/ml. Mean plasma concentrations of hANP-IR in uremic subjects were 324 pg/ml before and 113 pg/ml after hemofiltration or hemodialysis.

Identification of atrial natriuretic factor receptor of neuroblastoma N4TG1 cells: binding characteristics and photoaffinity labeling

We have found specific receptors for atrial natriuretic factor (ANF) in cultured neuroblastoma cells (N4TG1) of peripheral ganglionic origin. Scatchard analysis of the displacement binding revealed noninteracting, single-class binding sites with a KD of 1 X 10(-10) M and a density (Bmax) of 110,000-150,000 sites/cell. The cell-bound 125I-ANF was displaced by unlabeled ANF in a dose-dependent manner. Hormones unrelated to ANF such as angiotensins, adrenocorticotropic hormone, or arginine vasopressin were ineffective in displacing the cell-bound radioactivity. Using azidobenzoyl-125I-ANF as a photoaffinity ligand, an ANF receptor with an apparent Mr of 138,000 was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The addition of unlabeled ANF (1 microM) to the incubation medium completely abolished the labeling of this protein band, but atriopeptin I (1 microM) or angiotensins I, II, and III (each 1 microM) were not effective in inhibiting the affinity labeling. The treatment of the neuroblastoma cells with ANF stimulated intracellular cyclic GMP levels in a dose-dependent manner with an EC50 of 5 nM. ANF (1 X 10(-7) M) stimulated cyclic GMP accumulation in less than 5 min by 30-fold as compared to the controls.

Conversion of beta-human atrial natriuretic polypeptide into alpha-human atrial natriuretic polypeptide in human plasma in vitro

Using synthetic beta-human atrial natriuretic polypeptide (beta-hANP), an antiparallel dimer of alpha-hANP, and radioimmunoassay (RIA) for alpha-ANP which also detects beta-hANP, we investigated the disappearance profile and the change in the molecular form of exogenously added beta-hANP in human plasma in vitro, compared with those of alpha-hANP. The ANP-like immunoreactivity (ANP-LI) level in beta-hANP-added human plasma exhibited slower disappearance than that in alpha-hANP-added plasma during the incubation at 37 degrees C. High performance-gel permeation chromatography and reverse phase-high performance liquid chromatography coupled with RIA revealed that beta-hANP (6K) was converted into a smaller peptide with an approximate molecular weight of 3K corresponding to alpha-hANP during the incubation. Amino acid analysis and amino-terminal sequencing confirmed that the converted peptide from beta-hANP in human plasma is authentic alpha-hANP. The demonstrated conversion of beta-hANP into alpha-hANP in human plasma could be relevant to the in vivo natriuretic and diuretic actions with slower onset and longer duration of this unique peptide.

Human prepro atrial natriuretic factors 26-55, 56-92, and 104-123 increase renal guanylate cyclase activity

Human prepro atrial natriuretic factors 26-55, 56-92, and 104-123 as well as human atrial natriuretic factor (4-28) in the present investigation increased renal cortical and medullary cyclic GMP levels and maximally enhanced particulate guanylate cyclase activity [E.C. 4.6.1.2] two-fold in whole kidney homogenates, renal cortical and medullary membranes, and in isolated distal nephrons at their 1 microM concentrations. Dose-response relationships revealed that the half maximal [ED50] activation of guanylate cyclase was at their 10 nM concentrations in rat, rabbit, and dog kidneys. Both human atrial natriuretic factor and the prepro factors decreased adenylate cyclase activity. These results suggest that prepro factors 26-55, 56-92, 104-123 may also be functionally active.

Molecular forms of atrial natriuretic polypeptides circulating in human plasma

Molecular forms of atrial natriuretic polypeptides circulating in human plasma were analyzed by chromatographic separation, coupled with radioimmunoassay. Analyses were done with human plasma samples taken from 24 human subjects, divided into groups of healthy volunteers, patients with renal disease, and patients with heart disease, with 8 subjects in each group. Although alpha-hANP was found as a major circulating form in most of the plasma specimens (16 cases), beta-hANP accompanied by alpha-hANP was found in 6 cases including 2 healthy volunteers. In addition, hANP-immunoreactive macromolecule, which is likely a bound form of hANP, was found to some extent in all the specimens tested. Diversity of human plasma in ANP molecular distribution was discussed in connection with a radioimmunoassay for plasma ANP.

Primary structure of human carcinoembryonic antigen (CEA) deduced from cDNA sequence

The cDNAs corresponding to the mRNA encoding a polypeptide which is immunoreactive with the antisera specific to carcinoembryonic antigen (CEA) (1) are cloned. The amino acid sequences deduced from the nucleotide sequences of the cDNAs show that it is synthesized as a precursor with a signal peptide followed by 668 amino acids of the putative mature CEA peptide, whose N-terminal 24 amino acids and amino acids 286 to 295 exactly coincide with those known for N-terminal sequences of CEA (2) and NFA-1 (3), respectively. The first 108 N-terminal residues are followed by three very homologous repetitive domains of 178 residues each and then by 26 mostly hydrophobic residues which probably comprise a membrane anchor. Each repetitive domains contains 4 cysteines at precisely the same positions and as many as 28 possible N-glycosylation sites are found in the CEA peptide region agreeing with high carbohydrate content of purified CEA.

Effects of chronic salt loading on plasma atrial natriuretic peptide (ANP) in the spontaneously hypertensive rat

Plasma concentrations of immunoreactive atrial natriuretic peptide (ANP) was measured in spontaneously hypertensive rats (SHR) during chronic salt loading (1.5% NaCl in drinking water). During the 3-week experimental period mean arterial blood pressure, heart rate, urinary sodium excretion and body weight was assessed in salt-loaded as well as in control rats. The sodium excretion was more than 10-fold increased in the rats on the high salt diet. The plasma ANP concentration was significantly increased only 24 h after the start of the high salt intake. Thereafter plasma ANP concentrations were not significantly different from values obtained in control rats. The blood pressure was significantly increased after 3 weeks on the high salt diet. At the end of the 3-week experimental period the rats were subjected to a 10 and 20% acute volume expansion with homologous whole blood. During this intervention the increase in plasma ANP concentrations was blunted in the high salt rats compared to the control group. It is concluded that during chronic salt loading in SHR there is an initial rise in plasma ANP levels and that other hormonal and neuronal systems are more important in the long term maintenance of fluid and electrolyte balance.

Atrial natriuretic factor receptor on cultured Leydig tumor cells: ligand binding and photoaffinity labeling

Atrial natriuretic factor (ANF) is a peptide hormone discovered recently from the heart atrium that possesses potent natriuretic and vasorelaxant activities. Recently we found that ANF markedly stimulates intracellular cGMP and almost completely inhibits cAMP accumulation in testicular interstitial tumor cells [Pandey, K. N., Kovacs, W. J., & Inagami, T. (1985) Biochem. Biophys. Res. Commun. 133, 800-806]. These actions of ANF suggest the presence of ANF receptors in testicular interstitial cells. In this study, cultured murine Leydig tumor cells have been shown to contain specific binding sites for ANF. Saturation binding studies indicated a single class of binding sites with a Kd of 5 X 10(-9) M at a density of 2 X 10(6) sites/cell. The binding of mono[125I]iodo-ANF (125I-ANF) was competed by unlabeled ANF in a dose-dependent manner. Hormones unrelated to ANF such as angiotensin I, bovine luteinizing hormone, and human chorionic gonadotropin were not able to compete against 125I-ANF. The binding of 125I-ANF was rapid, reaching maximum levels in 15 min at 4 degrees C. At 37 degrees C, the cell-bound 125I label was quickly decreased. Pretreatment of cells with NH4Cl, chloroquine, or NaN3 resulted in significant increases in maximum levels of the cell-bound 125I radioactivity. A photoaffinity reagent for ANF receptor was prepared by reacting ANF with succinimido 4-azidobenzoate, and resultant 4-azidobenzoyl- (AZB-) ANF was purified by high-performance liquid chromatography (HPLC). AZB-ANF was radioiodinated by use of chloramine T and purified again by HPLC.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and biological properties of two dimeric forms of human alpha-atrial natriuretic peptide

Two dimeric forms of human alpha-atrial natriuretic peptide (alpha-ANP) were synthesized by solution methods and compared with monomeric alpha-ANP in terms of some biological and immunochemical properties. The parallel form (beta'-ANP) and the antiparallel form (beta-ANP) were equipotent in smooth muscle relaxant activity in isolated rat aorta and their ED50 values were estimated to be 1.7 X 10(-8) M and 1.6 X 10(-8) M, respectively. Diuretic and natriuretic responses induced by beta-ANP and beta'-ANP anesthetized rats were equally less potent but exhibited a significantly longer duration than those induced by alpha-ANP. beta-ANP and beta'-ANP possessed immunoreactivities of 60-100% and 50-90% (alpha-ANP, 100% on a molar basis), respectively, with three different antisera raised against alpha-ANP-related peptides.

Immunoreactive atrial natriuretic polypeptides in the adrenal medulla and sympathetic ganglia

Atrial natriuretic polypeptide (ANP)-like immunoreactivity was found in the rat adrenal gland by using indirect immunofluorescence and peroxidase-antiperoxidase techniques. ANP-like immunostaining was present in most of chromaffin cells with varying degrees of immunoreactivity. The majority of medullary cells displayed very intense immunostaining, and several clusters revealed weaker immunostaining. No staining was found in the adrenal cortex or in the nerve fibers in this organ. In the consecutive sections treated for dopamine-beta-hydroxylase (DBH), apparently all medullary cells had intense immunofluorescence for DBH and its distribution pattern was very similar to that for ANP-like immunoreactivity. While phenylethanolamine N-methyltransferase (PNMT) immunoreactive cells largely corresponded to the intensely stained ANP-like immunoreactive cells, suggesting that adrenaline cells contained a large amount of ANP-like substance, noradrenaline cells contained a smaller amount of this substance than adrenaline cells. Ultrastructural study showed that end-products due to the immunoreaction with the ANP antiserum were primarily associating with chromaffin granules. In addition, the presence of ANP-like immunoreactivity was investigated in several sympathetic ganglia of the rat. No principal ganglion cells were ANP-positive, whereas a few small intensely fluorescent (SIF) cells were ANP-immunoreactive. The present findings suggest that catecholamines coexist with ANP which has a natriuretic and vasodilating effect, in adrenal medullary cells and SIF cells in several rat sympathetic ganglia, but not in principal ganglion cells.

The atrial natriuretic factor

In less than three years since the rapid and potent natriuretic response to intravenous injection of atrial myocardial extract in rats was reported the factor responsible for the diuretic, natriuretic, and vasodilating activity of the atrial homogenates was isolated, its chemical structure elucidated, and its total synthesis achieved. Also the cDNA and the gene encoding for the atrial natriuretic factor in mice, rats, and man have been cloned and the chromosomal site identified. The major effects of this hormone are vasodilatation, prevention and inhibition of the contraction induced by noradrenaline and angiotensin II, diuresis, and natriuresis associated in most instances with a pronounced increase in glomerular filtration rate and filtration fraction, inhibition of aldosterone secretion, and considerable stimulation of particulate guanylate cyclase activity. High density specific binding sites have been demonstrated in the zona glomerulosa of the adrenal cortex, in the renal glomeruli, and in the collecting ducts, and in the brain areas involved in the regulation of blood pressure and of sodium and water (AV3V region, subfornical organ, nucleus tractus solitarius, area postrema).

Atrial natriuretic peptide mRNA is regulated by glucocorticoids in vivo

In these studies glucocorticoids were found to increase the plasma levels of atrial natriuretic peptide (ANP) as well as the expression of the ANP gene in the Sprague-Dawley rat. Plasma ANP rose two-fold after 48 hrs. of exposure to dexamethasone (1 mg/day) in both intact and adrenalectomized animals. This was accompanied by a 1.5-2.0 fold increase in the levels of atrial and ventricular ANP transcripts. Deoxycorticosterone acetate (5 mg/day), administered on the same schedule, failed to increase either plasma ANP levels or cardiac ANP mRNA accumulation. These effects suggest that ANP may have a potential role as a mediator of glucocorticoid activity in the cardiovascular system and support the hypothesis that ANP is a glucocorticoid-regulated gene.

Atrial natriuretic peptide and atrial pressure in patients with congestive heart failure

To define the relation between atrial pressures and the release of atrial natriuretic peptide, we measured plasma concentrations of the peptide in 26 patients with cardiac disease--11 with normal atrial pressures and 15 with elevated atrial pressures (11 of these 15 had elevated pressures in both atria). Mean peptide levels (+/- SEM) in the peripheral venous blood were increased in the 11 patients with cardiac disease and normal atrial pressures, as compared with 60 healthy controls (48 +/- 14 vs. 17 +/- 2 pmol per liter). In the patients with elevated atrial pressures, peptide concentrations were increased twofold in peripheral venous, right atrial, pulmonary arterial, and systemic arterial plasma, as compared with the concentrations in the patients with normal atrial pressures. A step-up in peptide concentration was seen between the venous and right atrial plasma (P less than 0.002) and between the pulmonary and systemic arterial plasma (P less than 0.01), suggesting release of the peptide from the atria. A linear relation was found between right atrial pressure and right atrial peptide concentration (r = 0.835, P less than 0.001) and between pulmonary wedge pressure and the systemic arterial peptide concentration (r = 0.866, P less than 0.001). Right atrial pressure and the peptide concentration both increased with exercise testing in the nine patients evaluated. We conclude that the release of atrial natriuretic peptide is at least partly regulated by right and left atrial pressures. Distinguishing the relative contributions of the two atria and defining the role of peptide release in the pathogenesis of heart failure will require further investigation.

Atrial natriuretic factor regulates steroidogenic responsiveness and cyclic nucleotide levels in mouse Leydig cells in vitro

The effects of synthetic atrial natriuretic factor (ANF) on the regulation of mouse Leydig cell steroidogenesis have been studied in vitro. ANF in nanomolar concentration increased testosterone production by more than 30-fold over basal levels. Concomitantly, cyclic guanosine monophosphate levels were increased 35-fold; cyclic adenosine monophosphate levels fell minimally (15-20%). ANF at low concentration (1 X 10(-11) M) inhibited testosterone production by luteinizing hormone-stimulated cells, while at higher concentration (greater than 2 X 10(-9) M) ANF stimulated steroidogenesis beyond the level attained by luteinizing hormone alone. These results indicate that ANF can exert stimulatory effects on testosterone steroidogenesis in vitro, and that the mechanism may involve an intracellular messenger other than cyclic adenosine monophosphate.

Immunocytochemical localization of atrial natriuretic factor, galanin and calcitonin gene-related peptide within the rat interpeduncular nucleus

The immunocytochemical localization of atrial natriuretic factor (ANF), galanin (GAL), and calcitonin gene-related peptide (CGRP) in specific subnuclei of the interpeduncular nucleus (IPN) was determined by immunocytochemistry in rats with and without intraventricular colchicine injection. ANF-positive processes were present within the ovoid regions of the rostral subnucleus, the dorsal lateral subnuclei, and were densely concentrated along the medial aspects of the lateral subnuclei in the caudal half of the IPN. GAL-positive processes were concentrated within the lateral subnuclei, in a narrow band extending over the central and intermediate subnuclei, and within the central subnuclei. GAL-positive cell bodies were present in a narrow band ventral to the rostral subnucleus, and in the ventrolateral corners of the caudal IPN. CGRP-positive processes were primarily localized within the dorsal lateral subnuclei and dorsal aspects of the lateral subnuclei. The presence of ANF, GAL and CGRP peptides within the IPN in patterns similar to previously described localizations of substance P, vasoactive intestinal peptide, serotonin and Leu-enkephalin provides a morphologic basis for modulation of complex physiological actions yet to be elucidated.

Atrial pressure and secretion of atrial natriuretic factor into the human central circulation

Atrial natriuretic factor, a peptide found in mammalian cardiac atria, has natriuretic and vasodilatory properties that may be important in the regulation of intravascular volume. To study factors related to its release in human subjects, intracardiac pressures and plasma atrial natriuretic factor concentrations in the central circulation were measured in 34 patients with a variety of cardiovascular disorders. Plasma atrial natriuretic factor concentration increased from the inferior vena cava to the right atrium (76 +/- 24 to 162 +/- 37 pg/ml, p less than 0.001) and from the vena cava to the aorta (76 +/- 24 to 177 +/- 46 pg/ml, p less than 0.001). Mean right atrial pressure was positively correlated with atrial natriuretic factor concentration in the pulmonary artery (r = 0.58, p less than 0.001), and mean pulmonary capillary wedge pressure was positively correlated with concentration in the aorta (r = 0.64, p less than 0.001). In six patients whose atrial natriuretic factor concentrations were measured at two different levels of atrial pressure, increased atrial pressure was accompanied by increased atrial natriuretic factor concentration in the pulmonary artery (p less than 0.01) and aorta (p less than 0.01). Atrial natriuretic factor levels measured in fresh myocardium from a patient undergoing cardiac transplantation showed tissue concentrations in the atria 500-fold higher than tissue concentrations in the ventricles. These data document that atrial natriuretic factor is found in human atrial myocardium and suggest that it may be released in response to increased atrial pressure. Such a secretory release mechanism is consistent with the hypothesis that atrial natriuretic factor plays a role in the regulation of circulatory volume.

Alpha-human natriuretic polypeptide (alpha-hANP) specific binding sites in bovine adrenal gland

The effects of synthetic alpha-human atrial natriuretic polypeptide (alpha-hANP) on steroidogenesis in bovine adrenocortical cells in primary monolayer culture were investigated. alpha-hANP did not inhibit basal aldosterone secretion. alpha-hANP induced a significant dose-dependent inhibition of basal levels of cortisol and dehydroepiandrosterone (DHEA) secretion and also of ACTH (10(-8) M)-stimulated increases in aldosterone, cortisol and DHEA secretion. Visualization of [125I]alpha-hANP binding sites in bovine adrenal gland by an in vitro autoradiographic technique demonstrated that these sites were highly localized in the adrenal cortex, especially the zona glomerulosa. These results suggest that the adrenal cortex may be a target organ for direct receptor-mediated actions of alpha-hANP.

Circulating atrial natriuretic peptides in conscious rats: regulation of release by multiple factors

Cardiocytes in the atria contain a prohormone that gives rise to atrial natriuretic peptides (ANP's), which have intrinsic hemodynamic regulatory activity. The distribution of ANP's in the brain suggests the involvement of these peptides in central cardiovascular regulation. In conscious rats with chronic indwelling catheters, volume loading with isotonic saline or glucose increased the amount of circulating immunoreactive ANP's by a factor of 4 to 5, as determined by radioimmunoassay. Hyperosmotic challenge with a hypertonic NaCl solution or anesthesia with halothane caused similar increases in plasma ANP's. Results obtained with the denervated-heart preparation indicate that neuronal influences are important in the release of ANP's induced by volume loading. As judged from reversed-phase high-performance liquid chromatography of extracted plasma and radioimmunoassay of collected fractions, the circulating physiologically important ANP's in the conscious rodent appear to be alpha-rANP(5-28) (atriopeptin III) and either alpha-rANP(3-28) [ANF(8-33)] or alpha-rANP(1-28) (ANF).

Identification of an endogenous protease that processes atrial natriuretic peptide at its amino terminus

We have partially purified a thiol-dependent protease from bovine atrial tissue that cleaves the Arg98-Ser99 bond of rat natriuretic peptide (Gly96-Tyr126) to produce the natriuretic Ser99-Tyr126 peptide (cardionatrin I). This was the only hydrolytic product we detected. The existence of the atrial natriuretic peptide system implicates the mammalian heart as an endocrine organ which participates in the hormonal regulation of extracellular fluid volume, electrolyte balance and vascular tone. This enzyme appears to be part of that system. The atrial protease also hydrolyzes the Arg-2-Napthylamide bond of natriuretic peptide stand-in substrates; on the basis of relative Vmax/Km as a measure of substrate specificity, Bz-Leu-Arg-Arg-2-Napthylamide (NA) greater than Bz-Leu-Arg-2-NA greater than Arg-2-NA. There is little or no cleavage between the Arg-Arg pair of the first substrate. Since in the Gly96-Tyr126 peptide the Arg-Arg pair is not the principle cleavage site for this enzyme, it is very unlikely that it is a principle cleavage site for this enzyme in pro-atrial natriuretic factor. It is possible that it is a cleavage site for a different enzyme or the pair may serve as a signal for cleavage at Arg98.