Atrial ANF Research Articles

Cold and warm infusion of Ringer's acetate in healthy volunteers: the effects on haemodynamic parameters, transcapillary fluid balance, diuresis and atrial peptides

The effects of Ringer's acetate (RAc) infusion with different temperatures, 18 degrees C compared to 36 degrees C, were studied in 20 healthy volunteers. An infusion volume of 20% of the estimated extracellular volume was given over 45 min. Before and after the RAc infusion, interstitial colloid osmotic pressure and interstitial fluid hydrostatic pressure were measured on the lateral part of the thorax and in the lower leg. Blood sampling and pressure measurements were performed through a cannula placed in the left radial artery, and arterial oxygen saturation was measured by pulse oximetry. Atrial peptides ANF (99-126) and ANF (1-98) in plasma were measured as indicators of volume loading. Cold RAc infusion increased mean arterial pressure from 82 (s.d. +/- 7) to 96 (s.d. +/- 9) mmHg (10.9-12.8 kPa) at the end of the infusion with a simultaneous fall in heart rate. Warm RAc infusion gave no changes in blood pressure or heart rate. The arterial oxygen saturation during the infusion of cold RAc was higher than during warm RAc infusion. Cold infusion produced the expected haemodilution with a fall in erythrocyte volume fraction (EVF) from 0.39 (+/- 0.03) to 0.33 (+/- 0.03) and a fall in plasma colloid osmotic pressure (COPp) from 21.7 (+/- 1.1) mmHg to 15.0 (+/- 1.3) mmHg (2.9-2.0 kPa). Warm infusion induced a nearly identical haemodilution. Interstitial colloid osmotic pressure fell from 11.6 (+/- 2.3) mmHg to 8.9 (+/- 2.7) mmHg (1.5-1.2 kPa) after warm infusion while cold infusion gave no changes. The changes in interstitial fluid hydrostatic pressure were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular forms of atrial natriuretic factor in normal and failing human myocardium.

Atrial natriuretic factor (ANF) is produced by myocardial tissue, and the plasma ANF concentration is known to be elevated in congestive heart failure (CHF). Data from animal models indicate that myocardial concentrations of ANF are depleted in CHF, and this has given rise to the hypothesis that CHF is characterized by depletion of stored ANF. To date, the molecular forms of ANF and their concentrations in atrial and ventricular myocardium remain poorly characterized in the normal and the failing human heart. We measured ANF concentrations in fresh tissue from failing human hearts explanted at the time of cardiac transplantation and from organ donors whose normal hearts could not be used for transplantation. We determined total ANF and alpha, beta, and gamma ANF concentrations in the right and left atrial appendages, atrial free walls, and ventricles. In normal hearts, ANF concentration in the atrial appendages was 40-fold higher than ANF in the rest of the atrial free wall and in the ventricles. In the failing hearts, atrial appendage ANF concentrations increased 5- to 10-fold, and atrial free wall ANF concentrations increased 200-fold. Analysis of molecular forms of ANF demonstrated significant increases in the gamma and beta forms in the left atrial appendage of failing hearts. alpha, beta, and gamma ANF forms were also significantly increased in right and left atrial free wall tissue from failing hearts. In addition, failing hearts were characterized by absolute and relative increases in the precursor form gamma ANF. These data from fresh tissues suggest that cardiac ANF stores are not decreased in severe CHF in humans; rather, chronic CHF is characterized by marked increases in atrial ANF tissue concentrations, particularly the beta and gamma ANF forms. These findings are consistent with intracellular accumulation of precursor ANF forms in severe chronic human CHF.

Comparative study of atrial peptides ANF (1-98) and ANF (99-126) as diagnostic markers of atrial distension in patients with cardiac disease

Mathisen P, Hall C, Simonsen S. Comparative study of atrial peptides ANF (1-98) and ANF (99-126) as diagnostic markers of atrial distension in patients with cardiac disease. Scand J Clin Lab Invest 1993; 53: 41-49.To evaluate the possible role of atrial natriuretic peptides ANF (1-98) and ANF (99–126) as diagnostic parameters of atrial distension, measurements of peptide levels were performed in 47 patients with chronic ischaemic and/or left sided valvular heart disease. Plasma samples were drawn from the pulmonary artery (PA) and superior vena cava (SVC) during diagnostic right heart catheterization. Forty of the patients also underwent left heart haemodynamic measurements, and in 28 patients two dimensional echocardiography with determination of left atrial diameter was performed.Enhanced plasma concentrations of both peptides were observed with increasing severity of heart failure assessed by the NYHA classification. Mean plasma levels of both peptides were closely correlated to mean pulmonary artery pressure (ANF (1-98): n=47, r=0.69 (SVC)/r=0.72 (PA), p<0.0001; ANF (99-126): n=46, r=0.75 (SVC)/r=0.68 (PA), p<0.0001) and mean pulmonary capillary wedge pressure (ANF (1-98): n=47, r=0.69 (SVC)/r=0.72 (PA), p<0.0001; ANF (99-126): n=46, r=0.70 (SVC)/r=0.64 (PA), p<0.0001). Positive correlations were also obtained between peptide levels and mean right atrial pressure and left ventricular end-diastolic pressure. When patients with high right atrial pressures (n=2) were excluded from analysis, a significant correlation was found between peptide levels and echocardiography assessed left atrial diameter.The present study demonstrates the close correlation between concentrations of both atrial peptides and cardiopulmonary haemodynamics in patients with chronic heart disease. The findings support the view that plasma levels of ANF (1-98) and ANF (99-126) are equally good indicators of atrial distension in these patients.

Secretion of immunoreactive ANF from FRTL-5 rat thyroid cells: regulation by calcium ionophore A23187

Atrial natriuretic factor-like immunoreactivity (ir-ANF) was characterized in a continuous line of rat thyroid follicular cells (FRTL-5) and the influence of the calcium ionophore A23187 on ir-ANF secretion was examined. Ir-ANF was identified by immunohistochemical staining as primarily reticular and juxtanuclear in short-term cultures, and more peripheral and granular in longer-term cultures, suggesting a process of ir-ANF packaging into secretory granules. The accumulation of ir-ANF granules was dependent upon the presence of thyrotropin (TSH) in the medium. Secreted ir-ANF was characterized using reversed-phase, high-performance liquid chromatography (RP-HPLC) and radioimmunoassay as a single peak eluting one fraction earlier than 125I-labeled rat ANF (99–126) (i.e., circulating atrial ANF) included as an internal standard. A23187 treatment of cells exhibiting primarily reticular ir-ANF caused a change to a pattern of more distinct, peripherally localized granules. This change occurred within 1 h after A23187 treatment and was dependent on the presence of Ca 2+ in the medium. In cultures containing primarily ir-ANF granules, A23187 (0.5 μg/ml) induced a peripheral translocation of the granules at 30 min and a complete degranulation by 7 h. Enzyme-linked immunoadsorbent assay (EIA) confirmed a dose-dependent effect of A23187 on ir-ANF release into the medium. These results suggest that some of the effects of Ca 2+ in the thyroid could be ascribed to its mobilization and release of ir-ANF, which in turn may have autocrine effects on thyroid follicular cells.

Thyroidal ANF: A possible mediator of autocrine regulation in the porcine thyroid gland

Atrial natriuretic factor immunoreactivity (ir-ANF) was examined in thyroid tissue sections and cultured thyroid cells using immunohistochemical staining with a monoclonal anti-ANF antibody. Localization of ir-ANF in perinuclear granules in cultured cells and in the basal region of follicular cells in sectioned tissue suggests that ir-ANF is a basally secreted product. Thyroidal ir-ANF was also characterized using reversed phase high performance liquid chromatography (RP-HPLC) of acidic thyroid extracts. An ir-ANF peak coeluting with synthetic rat ANF(99–126) suggests that thyroidal ir-ANF may be identical in form to circulating atrial ANF. However, the detection of ir-ANF in cultured thyroid cells confirms that the immunoreactivity is locally produced. Saturation analysis revealed high affinity ANF receptors ( K d =0.1 nM ; MBC=17.2 fmol/mg protein) on these cultured cells, and a competition study demonstrated the ability of extracted thyroidal ir-ANF to inhibit 125I rat ANF binding to the membrane receptors. The evidence presented here suggests that ir-ANF in the thyroid may be secreted locally to exert an autocrine effect on neighboring follicular cells.

Atrial structure and plasma ANF levels in rats with chronic diabetes mellitus

Atrial structure and plasma ANF levels in rats with chronic diabetes mellitus

Atrial natriuretic factor and autonomic nervous system function in man

To delineate a possible interaction of atrial natriuretic peptide ANF-(99-126) with autonomic nervous system function in humans, a spectrum of indices were assessed in 10 healthy young men during a 90 min iv administration of a) synthetic ANF-(99-126) 50 micrograms bolus followed by 0.025 micrograms.kg-1.min-1, b) the potent vasodilator sodium nitroprusside (SNP) 0.35 micrograms.kg-1. min-1, or c) vehicle 0.9% NaCl40 ml and 20% albumin 5 ml, in random sequence. Plasma immunoreactive ANF (irANF) rose from 32 to 1700 pg.ml-1 during the ANF-(99-126) infusion and was stable during SNP or vehicle. Infusion of ANF-(99-126) and SNP, but not vehicle, decreased diastolic blood pressure (BP) on average by -9 and -7.5%, respectively; systolic BP was largely unchanged. Heart rate (HR, + 15 and 12%) or plasma norepinephrine (NE) rose similarly during ANF-(99-126) and SNP infusions, and the systolic BP response to orthostasis was similar (-18 mmHg). The following autonomic indices did not differ significantly after the 3 infusions: responses of HR and NE to orthrostasis; reflex bradycardic response to phenylephrine (PE)-induced rise in systolic BP (+ 20 mmHg); responses of BP to hyperventilation, PE, or 3 min of sustained handgrip; and beat-to-beat variation (R-R interval) during deep breathing. The immediate orthostatic HR response (30/15 R-R interval ratio) fell similarly during infusion of ANF-(99-126) or nitroprusside. The findings indicate that in healthy men the function of the autonomic nervous system is not notably impaired by high circulating ANF levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Bovine adrenal chromaffin granules are a site of synthesis of atrial natriuretic factor

We have previously reported the existence of a peptide factor in the adrenal medulla which inhibits aldosterone secretion in cultured bovine zona glomerulosa cells. The acid extracts of chromaffin granules from bovine adrenal medulla were purified by a four step high performance liquid chromatography procedure. Two active fractions exhibited sequence homology with bovine atrial natriuretic factor ANF (Ser 99 – Tyr 126) and its polypeptide precursor (Asn 1 – Tyr 126). The occurence of both precursor and mature forms of ANF within chromaffin granules indicates the endogenous character of ANF in the adrenal medulla and suggests the potential usefulness of cultured adrenal chromaffin cells for investigating the synthesis, maturation and secretion of atrial peptides.

Plasma and atrial content of atrial natriuretic factor in cardiomyopathic hamsters

Immunoreactive atrial natriuretic factor (IR-ANF) was measured in plasma and atrial extracts from normal and cardiomyopathic Syrian golden hamsters. Plasma IR-ANF was increased from 84.8 ± 9.8 pg/ml(n = 17) to 234 ± 23 ( n = 25; P<.0001) in hamsters with moderate failure, and to 1085 ± 321 pg/ml (n = 10; P<.02) in animals with severe failure. Plasma IR-ANF increased with increased atrial hypertrophy. Atrial IR-ANF content was essentially the same in normal animals and in those with moderate heart failure (3.06 ± 0.28 vs 3.17 ± 0.19 μg/100 g body wt., P<.001) and lower in the majority of those with severe failure (1.82 μg/100 g body wt., P<.001). The elevations of IR-ANF in plasma are similar to those seen in patients with congestive heart failure. Our studies do not support bioassay results showing a deficiency of atrial ANF content as being important in the congestive heart failure associated with cardiomyopathy in the hamster.

Mechanisms of release of atrial natriuretic factor. II. Effect of chronic administration of α- and β-adrenergic and cholinergic agonists on plasma and atrial ANF in the rat

The effect that chronic subcutaneous infusion of α- and β-adrenergic and cholinergic agonists on plasma and atrial ANF was investigated. Isoproterenol, a β-adrenergic agonist, and carbachol, a cholinergic agonist produced a 3-fold increase in plasma ANF levels which were constant until the end of the infusion period. An increased natriuresis was observed in the same groups which was positively correlated with plasma ANF. No differences were observed in atrial content of ANF between the experimental groups. A sharp post-surgery decline in plasma ANF was observed in control, phenylephrine and epinephrine-treated groups which was maintained during the observation period of five days. This suggests that the rise in plasma ANF induced by isoproterenol and carbachol may be secondary to hemodynamic changes and not to direct receptor stimulation, and may play a role in the observed natriuresis. It is also suggested that the depression of plasma ANF may contribute to the well known post-surgery sodium retention.

Characterization and distribution of receptors for the atrial natriuretic peptides in mammalian brain.

Both rat 125I-labeled atrial natriuretic polypeptide [125I-ANP or atrial natriuretic factor fragment ANF-(99-126)] and human 125I-ANP [125I-alpha-ANP or human ANF-(99-126)] bind with high specificity and affinity (Kd = 20-80 pM) to an apparent single class of sites in guinea pig brain. The ligand selectivity pattern demonstrates that ANF-(101-126) greater than ANF-(99-126) greater than ANF-(103-125) greater than ANF-(103-123) on 125I-alpha-ANP binding sites. [International nomenclature starting at the end of the signal peptide of the recently sequenced prepropeptide is used; thus, ANF-(101-126) corresponds to the earlier designation ANF-(8-33), ANF-(103-123) to rat atriopeptin I, and ANF-(103-125) to rat atriopeptin II.] Similar results have been reported in peripheral tissues, which indicate that central and peripheral ANP binding sites have fairly similar structural requirements. In vitro receptor autoradiography shows that in the guinea pig brain, 125I-ANP binding sites are highly concentrated in the external plexiform layer of the olfactory bulb, subfornical organ, various thalamic nuclei, medial geniculate nucleus, and cerebellum. Lower densities are found in the central nucleus of the amygdala, dentate gyrus, hippocampus, and area postrema. Most remaining regions contain much lower densities of sites. In rat brain, 125I-ANP binding sites are differentially distributed, with high densities in the subfornical organ, area postrema, and linings of ventricles but low densities in the thalamus and cerebellum. In monkey brain, 125I-ANP binding sites are concentrated in the cerebellum. The presence of high densities of 125I-ANP binding sites in various brain regions strongly suggests the existence of a family of brain-heart peptides, in analogy to the well-known brain-gut peptides. Moreover, the extensive distribution of 125I-ANP binding sites in mammalian brain suggests that the possible roles of ANP/ANF-like peptides in brain are not restricted to the central regulation of cardiovascular parameters.

Reduction of blood pressure and increased diuresis and natriuresis during chronic infusion of atrial natriuretic factor (ANF Arg 101-Tyr 126) in conscious one-kidney, one-clip hypertensive rats.

Conscious one-kidney, one-clip hypertensive rats and their normotensive controls were infused during 7 days with synthetic ANF (Arg 101-Tyr 126) at 100 ng/hr/rat (35 pmol/hr/rat) by means of osmotic minipumps. The basal blood pressure of 193 +/- 6 mmHg gradually declined to 145 +/- 6 mmHg at day 4 after the infusion was started. No changes in blood pressure were observed in ANF-infused normotensive rats. A significantly higher diuresis and natriuresis was observed in ANF-infused hypertensive rats when compared to the non-treated hypertensive group. No such changes were observed in ANF-treated normotensive animals. No differences in PRA were seen in any group. Atrial immunoreactive ANF was significantly lower in one-kidney, one-clip rats than in the normotensive animals, but whether this is the reflection of an increased release in the circulation remains to be elucidated. It is suggested that the hypotensive response of one-kidney, one-clip animals to ANF may be secondary to a dual mechanism, vasodilatation and volume depletion.

Gluco- and mineralocorticoids may regulate the natriuretic effect and the synthesis and release of atrial natriuretic factor by the rat atria in vivo

Adrenalectomy abolished the acute natriuretic effect of ANF which was partially restored to about 50% by combined therapy with gluco- and mineralocorticoids. It is suggested that the lack of effect of ANF may be due to a decreased renal vascular reactivity to the peptide in adrenalectomized animals. Simultaneous administration of Dexamethasone and Deoxycorticosterone acetate to adrenalectomized rats produced a marked increase in immunoreactive ANF in atrial tissue and plasma. The administration of NaCl to these animals produced a relatively lower concentration of atrial ANF and a further increase in plasma ANF. Our results suggest that glucocorticoids may regulate synthesis and release of ANF by the atria and mineralocorticoids may have a permissive role. Furthermore, the presence of steroids is necessary for the NaCl-stimulated ANF release.