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

Atrial natriuretic factor--a circulating hormone stimulated by volume loading

The cardiocytes of mammalian cardiac atria contain granules very similar to those in endocrine cells. The number of these atrial granules is related directly to salt loading and blood volume. Furthermore, crude extracts of rat atria and granule preparations have powerful natriuretic and diuretic effects. These effects are mediated by peptides identified previously as atrial natriuretic factor (ANF). The peptides are derived from a common precursor, whose structure has been elucidated recently. Although there is indirect evidence from morphological studies that at least some of these peptides may be released into the blood and function as hormones, their presence in the blood has not yet been demonstrated. Here we describe a sensitive and specific radioimmunoassay for ANF and its stimulation on volume loading.

Occurrence of atrial natriuretic polypeptide in brain

In order to determine whether or not atrial natriuretic polypeptides (ANPs) exist in the brain, we have studied extracts from the rat brain using a specific radioimmunoassay (RIA) for alpha-atrial natriuretic polypeptide. The presence and widespread distribution of alpha-rat ANP-like immunoreactivity (alpha-rANP-LI) have been demonstrated in the rat brain. The highest concentration of alpha-rANP-LI (20-22 ng/g) is in the hypothalamus and the septum. Moderate concentrations of alpha-rANP-LI (2-8 ng/g) are also found in the midbrain, cerebral cortex, olfactory bulb, thalamus, pons-medulla and hippocampus. High performance gel permeation chromatography coupled with the RIA revealed that alpha-rANP-LI found in the rat brain consists of three components eluting at the positions of gamma-rat ANP (gamma-rANP), beta-rat ANP (beta-rANP) and alpha-rANP, respectively. Among these a low molecular weight form of alpha-rANP-LI emerging at the elution position corresponding to alpha-rANP is predominant in the rat brain. This is in contrast to the finding that gamma-rANP, a high molecular weight form of 13k daltons is the dominant form of alpha-rANP-LI in the rat atrium. These results clearly show that there exists a widespread neural system containing ANPs in the brain.

Renal, haemodynamic, and hormonal effects of human alpha atrial natriuretic peptide in healthy volunteers

The effects of atrial natriuretic peptide (ANP) were investigated in six healthy male volunteers taking a constant diet (120 mmol sodium and 60 mmol potassium daily). They were given an intravenous bolus of 100 micrograms human alpha-ANP on one day or placebo on another day 1-3 weeks apart in a double-blind randomised study. After ANP, urinary sodium excretion increased four-fold, and urine volume, calcium, magnesium, and phosphorus excretion doubled within 30 min of the injection. ANP induced an immediate fall in arterial pressure, followed by a longer vasodepressor phase which exceeded the duration of the effect on electrolyte excretion. There were no significant changes in plasma renin activity, aldosterone, antidiuretic hormone, or noradrenaline when compared with placebo.

Cyclic guanosine monophosphate mediates vascular relaxation induced by atrial natriuretic factor

The biochemical mechanism of action of synthetic atrial natriuretic factor (atriopeptin II) was studied in vascular smooth muscle of the rabbit thoracic aorta. Atriopeptin II caused a time-dependent and concentration-dependent increase in tissue levels of cyclic guanosine monophosphate that corresponded in these same tissues with vascular relaxation. The elevation of arterial cyclic guanosine monophosphate levels preceded the onset of vascular relaxation. Atriopeptin II did not alter vascular levels of cyclic adenosine monophosphate. The presence of a functionally intact vascular endothelium was not necessary for atriopeptin II to elicit vascular relaxation. Atriopeptin II-induced vascular relaxation and elevation of cyclic guanosine monophosphate levels were inhibited by the guanylate cyclase inhibitor methylene blue. These data suggest cyclic guanosine monophosphate mediates vascular relaxation produced by atriopeptin II.

Structural identification of beta- and gamma-human atrial natriuretic polypeptides

Atrial natriuretic polypeptides (ANPs) of varying chain length have been identified recently in human and rat atrial tissue. Their potent natriuretic-diuretic activities indicate their key role in the regulation of extracellular fluid volume and electrolyte balance. Furthermore, human and rat cDNAs encoding their precursor have been cloned and identified. Natriuretic-diuretic activity in human atrial extract comprises three distinct components (alpha, relative molecular mass (Mr) approximately 3,000; beta, Mr approximately 6,000; gamma, Mr approximately 13,000). However, only the 3,000-Mr peptide, alpha-human atrial polypeptide (alpha-hANP), comprising 28 amino acids, has so far been identified. We report here the purification and sequence analysis of two novel hANPs of higher Mr, beta- and gamma-hANP, both of which exhibit natriuretic and hypotensive activity. gamma-hANP, composed of 126 amino acids, carries the alpha-hANP sequence at its carboxy terminus. The identification of gamma-hANP reveals that the peptide, being the largest form of hANP, is processed directly from a 151-residue precursor by removal of a 26-residue signal peptide. In contrast, beta-hANP (56 residues) comprises an anti-parallel dimer of alpha-hANP; such a dimeric peptide possessing bioactivity has never been found in the tissue as an endogenous entity.

Nucleotide sequences of the human and mouse atrial natriuretic factor genes

Mouse and human atrial natriuretic factor (ANF) genes have been cloned and their nucleotide sequences determined. Each ANF gene consists of three coding blocks separated by two intervening sequences. The 5' flanking sequences and those encoding proANF are highly conserved between the two species, while the intervening sequences and 3' untranslated regions are not. The conserved sequences 5' of the gene may play an important role in the regulation of ANF gene expression.

Radioimmunoassay for alpha-human and rat atrial natriuretic polypeptide

Using a synthetic common carboxy-terminal fragment of alpha-human atrial natriuretic polypeptide (alpha-hANP) and alpha-rat atrial natriuretic polypeptide (alpha-rANP), we have produced an antiserum for alpha-ANP(17-28) and established a radioimmunoassay (RIA) for alpha-ANP that recognizes alpha-hANP and alpha-rANP equally. High performance gel permeation chromatography coupled with the RIA revealed that alpha-hANP-like immunoreactivity (alpha-hANP-LI) in the human atrium consists of three major components, gamma-hANP, alpha-hANP and another. On the other hand, alpha-rANP-LI in the rat atrium comprised at least two components, 13K alpha-rANP-LI and 3K-5K alpha-rANP-LI, which were presumably gamma-rANP and beta-rANP, respectively. Thus, considerable amounts of gamma-hANP and gamma-rANP are present in human right auricles and rat atria, respectively. The RIA established in this study provides a useful tool to investigate the pathophysiological significance of alpha-ANP and related peptides in cardiovascular disorders and shows that gamma-ANP is not only a precursor of alpha-ANP but acts as an important hormone.

Biochemical studies of rat atrial natriuretic factor

The natriuretic substances were purified from rat atrium (ANF, atrial natriuretic factor) and were shown to be identical with the inhibitor of norepinephrine-induced contraction of smooth muscle. Their four native forms were isolated. Amino acid sequence analyses showed they are peptides with 35, 31, 30 and 25 amino acid residues respectively and contain a ring structure consisting of 17 amino acid residues and a disulfide bridge. The presence of a high molecular weight prohormone was shown. cDNA coding for the precursor was cloned and used to deduce the amino acid sequence of the preprohormone. Genomic DNA for ANF was cloned and the presence of two introns were found. Several ANF peptides were synthesized. Structure-function studies showed that the ring structure is essential for the activity. Antibodies produced against the synthetic 25 amino acid residue ANF were used to develop radioimmunoassay. The presence of ANF in rat plasma was demonstrated as evidence that ANF is a circulating hormone. ANF was also found in the hypothalamus of rats. The quantitative determination of the synthetic ability of ANF has been determined by the application of ANF cDNA for the quantification of ANF messenger RNA. Immunohistochemical methods localized ANF in cardiac atriocytes, gonadotrophs in anterior pituitary and adrenal medulla (chromaffin cells). A strong immuno-reactivity was found in dark cells of the collecting ducts of the kidney. ANF increases cyclic GMP in target cells suggesting that cyclic GMP may be the intracellular mediator of ANF action.

Renal and systemic effects of atrial natriuretic factor

A survey of the literature reporting the in vivo biological activity of atrial natriuretic factor (ANF) is presented. Both the atrial extracts, in which ANF was first identified, and the peptides which have more recently been synthesized, have been shown to possess diuretic and saluretic properties. In addition, ANF decreased blood pressure and affected levels of aldosterone, renin, vasopressin and guanosine 3',5'-cyclic monophosphate (cGMP). The available evidence concerning likely mechanisms of action of ANF are presented and a pivotal role of ANF is suggested for blood pressure and volume regulation.

Cloning of genomic DNA for human atrial natriuretic factor

A human genomic DNA clone for atrial natriuretic factor (ANF) gene was isolated from a human gene library using the previously cloned cDNA for rat ANF as a probe. Partial nucleotide sequencing of the cloned DNA revealed the location of a 120-bp long intron between Lys-41 and Asn-42 of the ANF precursor. Restriction mapping also suggested the existence of at least one other intron in or proximal to the 3' -untranslated region.

Gene structure of human cardiac hormone precursor, pronatriodilatin

Atrial cardiocytes contain granules typical of protein-secreting cells, and atrial extracts are known to contain a powerful natriuretic and diuretic activity and to possess smooth muscle relaxant activity. A variety of active atrial peptides have been isolated, including a family of related peptides showing natriuretic, diuretic and smooth muscle relaxant activities in rat and human atria; these peptides were named atrial natriuretic factor (ANF). Another unrelated peptide from pig atria, cardiodilatin, is thought to possess only smooth muscle relaxant activity. Its partial amino acid sequence shows no homology with ANF sequences. The sequence analysis of a large form (106 amino acids) of ANF and of ANF complementary DNA clones indicates that cardiodilatin and ANF peptides are synthesized from a common precursor. This precursor also contains a signal peptide sequence expected of a secretory protein. We now describe the complete structure and sequence of the human gene for this novel hormone precursor that we call pronatriodilatin.

Nucleotide sequence of the gene encoding human atrial natriuretic factor precursor

The mammalian atrium is an endocrine organ that may be involved in the control of blood pressure and extracellular fluid volume. A series of peptides, which seem to be associated with atrium-specific secretory granules, have potent natriuretic, diuretic and smooth muscle relaxant activities. Sequence determination of several of these peptides, which range from 21 to 126 amino acids long, shows that they form a family, derived from a common precursor. Rat and human complementary DNAs that encode the precursor to the various peptides, collectively called atrial natriuretic factors (ANFs), have been cloned. Nucleotide sequencing showed that the ANFs are located at the C-terminus of a polypeptide of relative molecular mass 13,000. We describe here the isolation and characterization of the corresponding human gene. Two introns interrupt the gene; one is located in the region coding for the N-terminus of the precursor and the other separates the codon for the C-terminal tyrosine from the rest of the peptide.

Identification of rat gamma atrial natriuretic polypeptide and characterization of the cDNA encoding its precursor

Diuretic and smooth muscle-relaxing peptides, designated atrial natriuretic peptides (ANPs), have been identified in human and rat atrial tissues and implicated in the control of fluid volume and vascular function. Recently, cDNAs encoding the human and rat ANP precursors have been sequenced. We previously isolated from human tissue a natriuretic peptide of molecular weight (MW) 13,000 (gamma-hANP) comprising 126 amino acid residues, the largest natriuretic peptide so far identified, and showed that it is directly derived from the 151-residue human ANP precursor by the removal of a signal peptide. We now report the isolation and sequence analysis of a novel rat atrial natriuretic peptide (gamma-rANP) of MW 13,000, which derives from the rat ANP precursor. We also report the molecular cloning and nucleotide sequence analysis of the cDNA of the 152-residue rat ANP precursor, which is remarkably similar to the human 151-residue precursor (pre-hANP) except at the C-terminus. Differences in the rat and human precursor nucleotide sequences around the termination codons lead to a difference in processing pattern.

Atrial natriuretic factor (ANF) binding sites in brain and related structures

Visualization of [125I]ANF binding sites in rat brain by an autoradiographic technique demonstrated that these sites are highly localized in areas such as the olfactory bulb, subfornical organ, area postrema and nucleus tractus solitarius. This distribution suggests that certain cardiovascular effects of ANF could be centrally mediated and that the existence of brain ANF-related peptides should be considered. Finally, moderate densities of [125I]ANF binding sites are found in the rat and guinea pig eye while low densities are seen in pituitary and pineal gland.

Characterization and localization of atriopeptin in rat atrium

An antiserum specific for atriopeptin was used to characterize and localize atriopeptin-like immunoreactive material in rat atrium by radioimmunoassay and immunohistochemical techniques. The antiserum recognizes atriopeptin I, atriopeptin III, and alpha-human atrial natriuretic polypeptide, but does not recognize met-enkephalin, cholecystokinin, dynorphin A, bradykinin, substance P, or beta-endorphin. A high content of atriopeptin was found in crude extracts of rat atria, as compared to ventricles, and the atriopeptin-like immunoreactive material was found to be located exclusively in granules within atrial cardiocytes. Fractionation of the immunoreactive material by gel filtration and reverse-phase HPLC revealed the presence of multiple atriopeptins.

Molecular cloning and characterization of DNA sequences encoding rat and human atrial natriuretic factors

A cDNA copy of the message encoding rat atrial natriuretic factor (ANF) has been cloned in Escherichia coli, and its nucleotide sequence was determined. ANF appears to be synthesized as a larger precursor, atrial pronatriodilatin. The cDNA has an open reading frame potentially encoding a protein of 152 amino acids, of which the first 24 amino acids strongly resemble a signal sequence. This is followed by a sequence with 80% homology to a second vasoactive protein, porcine cardiodilatin. The ANF peptide is contained in the COOH-terminal portion of the protein. The DNA sequence corresponding to human ANF is also presented and displays a high degree of homology to its rat counterpart. These data provide further evidence for the expression in cardiac atria of a multifactor system that may contribute to the regulation of blood pressure and extracellular fluid volume.

mRNA sequence for human cardiodilatin–atrial natriuretic factor precursor and regulation of precursor mRNA in rat atria

The mammalian cardiac atrium has recently been shown to contain numerous peptides that exert marked effects on kidney function and vascular resistance. With one exception, the peptides have potent natriuretic and diuretic activities, and sequence similarities suggest that they may be derived from a common atrial natriuretic factor (ANF) precursor. The exception, cardiodilatin (CDD), differs from the ANF peptides in possessing potent vasorelaxant activity, but not natriuretic and diuretic activities. Here we report the cloning and sequence analysis of the cDNA for the human precursor protein (preproCDD-ANF) containing both the CDD and ANF sequences. The CDD sequence represents the N-terminal sequence preceded directly by a signal peptide, while the ANF sequence is present at the C-terminal end of the protein. Using hybridization analysis, we further show that the amount of rat preproCDD-ANF mRNA, which is synthesized selectively in the atria but not the ventricles, markedly decreases on water deprivation, suggesting that the water-electrolyte balance may be an important factor in the regulation of the expression of the preproCDD-ANF gene.