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Blaustein MP, Hamlyn JM. Sensational site: the sodium pump ouabain-binding site and its ligands. Am J Physiol Cell Physiol 2024; 326:C1120-C1177. [PMID: 38223926 DOI: 10.1152/ajpcell.00273.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 12/22/2023] [Accepted: 01/10/2024] [Indexed: 01/16/2024]
Abstract
Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
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Buckalew VM. Endogenous digitalis-like factors: an overview of the history. Front Endocrinol (Lausanne) 2015; 6:49. [PMID: 25918512 PMCID: PMC4394700 DOI: 10.3389/fendo.2015.00049] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 03/24/2015] [Indexed: 12/22/2022] Open
Abstract
The sodium pump is a ubiquitous cell surface enzyme, a Na, K ATPase, which maintains ion gradients between cells and the extracellular fluid (ECF). The extracellular domain of this enzyme contains a highly conserved binding site, a receptor for a plant derived family of compounds, the digitalis glycosides. These compounds inhibit the enzyme and are used in the treatment of congestive heart failure and certain cardiac arrhythmias. The highly conserved nature of this enzyme and its digitalis receptor led to early suggestions that endogenous regulators might exist. Recent examination of this hypothesis emerged from research in two separate areas: the regulation of ECF volume by a natriuretic hormone (NH), and the regulation of peripheral vascular resistance by a circulating inhibitor of vascular Na, K ATPase. These two areas merged with the hypothesis that NH and the vascular Na, K ATPase inhibitor were in fact the same entity, and that it played a causative role in the pathophysiology of certain types of hypertension. The possibility that multiple endogenous digitalis-like factors (EDLFs) exist emerged from efforts to characterize the circulating enzyme inhibitory activity. In this review, the development of this field from its beginnings is traced, the current status of the structure of EDLFs is briefly discussed, and areas for future development are suggested.
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Affiliation(s)
- Vardaman M. Buckalew
- Medical Center Boulevard, Wake Forest School of Medicine, Winston Salem, NC, USA
- *Correspondence: Vardaman M. Buckalew, Medical Center Boulevard, Wake Forest School of Medicine, Winston Salem, NC 27157, USA e-mail:
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Kramer HJ. Identification of Putative Natriuretic Hormones Isolated from Human Urine. Front Endocrinol (Lausanne) 2015; 6:66. [PMID: 26052310 PMCID: PMC4440383 DOI: 10.3389/fendo.2015.00066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 04/14/2015] [Indexed: 11/24/2022] Open
Abstract
This brief review describes some representative methodological approaches to the isolation of putative endogenous inhibitors of epithelial sodium transport - i.e., as ouabain-like factors (OLF) that inhibit the sodium transport enzyme Na-K-ATPase or inhibit the epithelial sodium channel (ENaC). Gel chromatography and reverse-phase (RP)-high performance liquid chromatography (HPLC) of lyophilized and reconstituted 24 h-urine from salt-loaded healthy humans led to two active fractions, a hydrophilic OLF-1 and a lipophilic OLF-2, whose mass (Ms)-spectroscopic data indicate a Mr of 391 (1, 2). Further identification was attempted by Ms-, infrared (IR)-, ultraviolet (UV)-, and (1)H-NMR-spectroscopy. OLF-1 and OLF-2 may be closely related if not identical to (di)ascorbic acid or its salts such as vanadium (V)-V(v)-diascorbate with Mr 403 (3) and V(IV)-diascorbate. OLF-1 and V(v)-diascorbate are about 10-fold stronger inhibitors of Na-K-ATPase than OLF-2 and V(IV)-diascorbate, respectively. In conscious rats, i.v. infusion of OLF-1 and OLF-2 resulted in a strong natriuresis. In a similar study, Cain et al. (4) isolated a sodium transport inhibitor from the urine of uremic patients by gel chromatography and RP-HPLC. In uremic rats, a natriuretic response to the injection of the active material was found. Xanthurenic acid 8-O-β-d-glucoside (Mr 368) and xanthurenic acid 8-O-sulfate (Mr 284) were identified as endogenous inhibitors of sodium transport acting, e.g., by ENaC blockade. No definite relation to blood pressure, body fluid volume, or sodium balance has been reported for any of these above factors, and further studies to identify the natriuretic and/or ouabain-like compound(s) or hormone(s) will be needed.
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Affiliation(s)
- Herbert J. Kramer
- Center of Internal Medicine, Rheinische-Friedrich-Wilhelms-University, Bonn, Germany
- *Correspondence: Herbert J. Kramer, Center of Internal Medicine, Rheinische-Friedrich-Wilhelms-University, Sigmund-Freud-Strasse 25, Bonn D-53127, Germany,
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Kerek F, Voicu VA. Spherical Oligo-Silicic Acid SOSA Disclosed as Possible Endogenous Digitalis-Like Factor. Front Endocrinol (Lausanne) 2014; 5:233. [PMID: 25667581 PMCID: PMC4304351 DOI: 10.3389/fendo.2014.00233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 12/16/2014] [Indexed: 11/15/2022] Open
Abstract
The Na(+)/K(+)-ATPase is a membrane ion-transporter protein, specifically inhibited by digitalis glycosides used in cardiac therapy. The existence in mammals of some endogenous digitalis-like factors (EDLFs) as presumed ATPase ligands is generally accepted. But the chemical structure of these factors remained elusive because no weighable amounts of pure EDLFs have been isolated. Recent high-resolution crystal structure data of Na(+)/K(+)-ATPase have located the hydrophobic binding pocket of the steroid glycoside ouabain. It remained uncertain if the EDLF are targeting this steroid-receptor or another specific binding site(s). Our recently disclosed spherical oligo-silicic acids (SOSA) fulfill the main criteria to be identified with the presumed EDL factors. SOSA was found as a very potent inhibitor of the Na(+)/K(+)-ATPase, Ca(2+)-ATPase, H(+)/K(+)-ATPase, and of K-dp-ATPase, with IC50 values between 0.2 and 0.5 μg/mL. These findings are even more astonishing while so far, neither monosilicic acid nor its poly-condensed forms have been remarked biologically active. With the diameter ϕ between 1 and 3 nm, SOSA still belong to molecular species definitely smaller than silica nano-particles with ϕ > 5 nm. In SOSA molecules, almost all Si-OH bonds are displayed on the external shell, which facilitates the binding to hydrophilic ATPase domains. SOSA is stable for long term in solution but is sensitive to freeze-drying, which could explain the failure of countless attempts to isolate pure EDLF. There is a strong resemblance between SOSA and vanadates, the previously known general inhibitors of P-type ATPases. SOSA may be generated endogenously by spherical oligomerization of the ubiquitously present monosilicic acid in animal fluids. The structure of SOSA is sensitive to the concentration of Na(+), K(+), Ca(2+), Mg(2+), and other ions suggesting a presumably archaic mechanism for the regulation of the ATPase pumps.
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Affiliation(s)
- Franz Kerek
- SiNatur GmbH, Martinsried, Germany
- *Correspondence: Franz Kerek, SiNatur GmbH, Am Klopferspitz 19, IZB, 82152 Munich, Germany e-mail:
| | - Victor A. Voicu
- Department of Clinical Pharmacology, Toxicology and Psychopharmacology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
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Gonick HC. Evidence for a 12 kDa "Carrier Protein" for Natriuretic Hormone. Front Endocrinol (Lausanne) 2014; 5:196. [PMID: 25477863 PMCID: PMC4237141 DOI: 10.3389/fendo.2014.00196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 10/30/2014] [Indexed: 11/21/2022] Open
Abstract
The search for the elusive Na-K-ATPase-inhibiting natriuretic hormone continues. In this review, evidence is presented that isolating the carrier protein for natriuretic hormone from hypertensive plasma is a necessary first step before splitting off the final hormone. The carrier protein has a molecular weight of 12 kDa while the final hormone has a molecular weight of 408 Da. Both compounds inhibit Na-K-ATPase but the compound containing the carrier protein predominates. The question has been raised as to whether the carrier protein is in actuality proANF, a 17 kDa protein that can be split between a 14 kDa protein (the presumptive proANF) and the 3 kDa ANF.
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Affiliation(s)
- Harvey C. Gonick
- Division of Nephrology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
- *Correspondence: Harvey C. Gonick, 201 Tavistock Avenue, Los Angeles, CA 90049, USA e-mail:
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Xie JX, Shapiro AP, Shapiro JI. The Trade-Off between Dietary Salt and Cardiovascular Disease; A Role for Na/K-ATPase Signaling? Front Endocrinol (Lausanne) 2014; 5:97. [PMID: 25101054 PMCID: PMC4101451 DOI: 10.3389/fendo.2014.00097] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 06/07/2014] [Indexed: 12/12/2022] Open
Abstract
It has been postulated for some time that endogenous digitalis-like substances, also called cardiotonic steroids (CTS), exist, and that these substances are involved in sodium handling. Within the past 20 years, these substances have been unequivocally identified and measurements of circulating and tissue concentrations have been made. More recently, it has been identified that CTS also mediate signal transduction through the Na/K-ATPase, and consequently been implicated in profibrotic pathways. This review will discuss the mechanism of CTS in renal sodium handling and a potential "trade-off" effect from their role in inducing tissue fibrosis.
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Affiliation(s)
- Joe X. Xie
- Department of Medicine, University of Colorado School of Medicine, Aurora, CO, USA
| | - Anna Pearl Shapiro
- Department of Medicine, University of Toledo College of Medicine, Toledo, OH, USA
| | - Joseph Isaac Shapiro
- Department of Medicine, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV, USA
- *Correspondence: Joseph Isaac Shapiro, Department of Medicine, Joan C. Edwards School of Medicine, Marshall University, 1600 Medical Center Drive Suite 3408, Huntington, WV 25701, USA e-mail:
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Lingrel JB. The physiological significance of the cardiotonic steroid/ouabain-binding site of the Na,K-ATPase. Annu Rev Physiol 2010; 72:395-412. [PMID: 20148682 DOI: 10.1146/annurev-physiol-021909-135725] [Citation(s) in RCA: 220] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The Na,K-ATPase is the membrane "pump" that generates the Na(+) and K(+) gradients across the plasma membrane that drives many physiological processes. This enzyme is highly sensitive to inhibition by cardiotonic steroids, most notably the digitalis/ouabain class of compounds, which have been used for centuries to treat congestive heart failure and arrhythmias. The amino acids that constitute the ouabain-binding site are highly conserved across the evolutionary spectrum. This could be fortuitous or could result from this site being conserved because it has an important biological function. New physiological approaches using genetically engineered mice are being used to define the biological significance of the "receptor function" of the Na,K-ATPase and its regulation by potential endogenous cardiotonic steroid-like compounds. These studies extend the reach of earlier studies involving the biochemical purification of endogenous regulatory ligands.
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Affiliation(s)
- Jerry B Lingrel
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0524, USA.
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Weiler EW, Gonick HC, Prins BA, Purdy RE, Weber MA. Characterization of a low molecular weight Na-K-ATPase inhibitor of urinary origin. Am J Med Sci 1994; 307:27-35. [PMID: 8291503 DOI: 10.1097/00000441-199401000-00005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
It has been demonstrated that expansion of extracellular fluid volume induces the release of a low-molecular-weight natriuretic and sodium-potassium-activated adenosine triphosphatase inhibiting hormone (NKAI). In this study, we used a highly purified hormone extracted from pooled hypertensive urines (u-NKAI). Like ouabain, this compound was found to be a potent inhibitor of the sodium-potassium-activated adenosine-triphosphatase and potassium-stimulated paranitrophenyl phosphatase enzyme systems as well as a vasoconstrictor in vitro. In contrast to ouabain, which is a competitive inhibitor of both enzyme systems with respect to potassium, u-NKAI is noncompetitive. Furthermore, u-NKAI differs from ouabain by its lack of cross-reactivity with digoxin antibodies. In addition, whereas ouabain binds to both high-affinity and low-affinity binding sites on the sodium-potassium-activated adenosine-triphosphatase enzyme in the absence of potassium, u-NKAI binds only to the low-affinity binding sites. This study demonstrates that the highly purified u-NKAI, although ouabain-like in certain respects, is not an "endogenous ouabain."
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Affiliation(s)
- E W Weiler
- Trace Element Laboratory, Division of Nephrology/Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048
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Yuan CM, Manunta P, Hamlyn JM, Chen S, Bohen E, Yeun J, Haddy FJ, Pamnani MB. Long-term ouabain administration produces hypertension in rats. Hypertension 1993; 22:178-87. [PMID: 8340153 DOI: 10.1161/01.hyp.22.2.178] [Citation(s) in RCA: 129] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Ouabain has recently been identified as an endogenous Na(+)-K+ pump inhibitor. We administered ouabain chronically to normotensive rats with varying degrees of reduced renal mass (RRM) and to normal two-kidney rats to see whether hypertension could be produced. Normal male Wistar rats and rats with 25%, 60%, and 70% RRM received ouabain (13.9 micrograms/kg per day IP) in normal saline for 4 weeks followed by ouabain (27.8 micrograms/kg per day IP) for 3 to 4 more weeks. Respective control animals received vehicle only. Blood pressure was recorded weekly by tail plethysmography. Animals received tap water and standard rat chow, except for 70% RRM rats, which received distilled water and sodium-free chow. After 6 to 8 weeks of treatment, with rats under thiobutabarbital anesthesia, direct blood pressure was determined. Plasma, tissue, and urinary ouabain levels were measured with a specific radioimmunoassay. Animals receiving ouabain developed significant increases in mean blood pressure compared with control animals (70% RRM, 147 +/- 4 vs 116 +/- 4 mm Hg; 60% RRM, 140 +/- 4 vs 107 +/- 3 mm Hg; 25% RRM, 131 +/- 5 vs 100 +/- 2 mm Hg; no RRM, 116 +/- 4 vs 98 +/- 5 mm Hg). Plasma ouabain levels measured 24 hours after the last ouabain dose were not different in animals receiving ouabain vs those receiving vehicle. However, kidney tissue ouabain levels were significantly greater (6.39 +/- 1.17 vs 2.36 +/- 0.52 micrograms/kg, P < .05) in animals receiving ouabain. In conclusion, ouabain, given chronically, is associated with the development of hypertension in RRM rats as well as in normal rats. Blood pressure was greater in animals with greater degrees of RRM for a given ouabain dose.
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Affiliation(s)
- C M Yuan
- Department of Physiology, Uniformed Services University of the Health Sciences, Bethesda, Md
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Yamada H, Ihara N, Takahashi H, Yoshimura M, Sano Y. Distribution of the endogenous digitalis-like substance (EDLS)-containing neurons labeled by digoxin antibody in hypothalamus and three circumventricular organs of dog and macaque. Brain Res 1992; 584:237-43. [PMID: 1325245 DOI: 10.1016/0006-8993(92)90900-t] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Endogenous digitalis-like substance (EDLS) is a newly discovered humoral agent which causes sodium-diuresis. EDLS is well known to have inhibitory activity to Na+,K(+)-ATPase and cross-immunoreactivity to digoxin antibody; however, its precise chemical structure has not yet been determined. We had previously developed a histochemical technique for EDLS, i.e., digoxin-immunohistochemistry, and demonstrated that EDLS was produced in the hypothalamic neurons. In the present study, the distribution of EDLS-containing neurons in the hypothalamus of dog and macaque was investigated using this technique, because anti-EDLS antibody cannot be obtained yet. In both species, EDLS neuronal somata were mainly localized in the paraventricular nucleus and the supraoptic nucleus and its accessory nuclei. A number of somata were also scattered in the other hypothalamic areas. The processes of these neurons ran from the area where the somata were located, through the lateral and basal area of the hypothalamus, to the infundibulum. These nerve fibers with varicosities were associated with the primary capillaries of hypophysial portal veins. A few immunopositive nerve fibers were also seen in the pituitary posterior lobe of both species. Intensive immunoreactivities were observed in the subfornical organ and organum vasculosum laminae terminalis. There were no differences between dog and macaque.
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Affiliation(s)
- H Yamada
- Department of Anatomy, Shiga University of Medical Science, Otsu, Japan
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Okada K, Caramelo C, Tsai P, Schrier RW. Effect of inhibition of Na+/K(+)-adenosine triphosphatase on vascular action of vasopressin. J Clin Invest 1990; 86:1241-8. [PMID: 2170449 PMCID: PMC296854 DOI: 10.1172/jci114830] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The present study was undertaken to examine the cellular interaction between a Na+/K(+)-ATPase inhibitor, ouabain, and arginine vasopressin (AVP) in rat vascular smooth muscle cells (VSMC) in culture. Preincubation with 10(-5) M ouabain for 60 min increased basal cytosolic free Ca2+ [( Ca2+]i) concentration and intracellular 45Ca2+ uptake. Ouabain, however, did not affect basal 45Ca2+ efflux or AVP-stimulated 45Ca2+ efflux. As assessed by cell shape change, preincubation with 10(-5) M ouabain for 60 min also enhanced the sustained cellular contractile effect of a submaximal (10(-8) M AVP, 21.5% vs. 30.5%, P less than 0.01) but not maximal dose of 10(-6) M AVP. Preincubation with 10(-5) M ouabain for 60 min did not change AVP-induced V1-specific surface receptor binding or AVP-induced inositol phosphate production but did however potentiate the mobilization of [Ca2+]i induced by a submaximal (10(-8) M AVP, 301 vs. 385 nM, P less than 0.01) but not a maximal dose of AVP. These effects of ouabain on the mobilization of [Ca2+]i were abolished by incubation in Ca2(+)-free buffer or 5 X 10(-5) M verapamil. Ouabain (10(-5) M) also enhanced the sustained cellular contractile effect of a direct protein kinase C activator, phorbol 12-myristate 13-acetate. The present results therefore indicate that the inhibition of Na+/K(+)-ATPase may enhance the vascular action of AVP, and perhaps other vasoconstrictors, by increasing the AVP-induced mobilization of [Ca2+]i and by potentiating the activity of protein kinase C stimulated by AVP through enhancing basal and AVP-stimulated cellular Ca2+ uptake.
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Affiliation(s)
- K Okada
- Department of Medicine, University of Colorado School of Medicine, Denver 80262
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Cloix JF. Endogenous digitalislike compounds. A tentative update of chemical and biological studies. Hypertension 1987; 10:I67-70. [PMID: 2824369 DOI: 10.1161/01.hyp.10.5_pt_2.i67] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Endogenous digitalislike compound (or compounds) has been described as involved in some diseases. Questions remain concerning its chemical nature, origin, and biological properties. The methods of measuring the compound are based on biological properties of digitalis, mainly Na+, K+-adenosine triphosphatase (ATPase) inhibition and related properties. Chemically, digitalislike compound has been described as a peptide, as fatty acids, and as a steroid. Its origin could be the brain, particularly the hypothalamus and pituitary gland. The adrenal glands were also proposed as its origin. The reported biological properties of digitalislike compound are mainly dependent on Na+, K+-ATPase inhibition. No definitive conclusions can be drawn from the available data.
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Affiliation(s)
- J F Cloix
- Department of Pharmacology, Necker Hospital, Paris, France
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13
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Deray G, Rieu M, Devynck MA, Pernollet MG, Chanson P, Luton JP, Meyer P. Evidence of an endogenous digitalis-like factor in the plasma of patients with acromegaly. N Engl J Med 1987; 316:575-80. [PMID: 3027557 DOI: 10.1056/nejm198703053161003] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Evidence suggests that plasma-volume expansion leads to the release of a digitalis-like factor, which is thought to act on the renal tubular cells and cause natriuresis. We postulated that this factor might be present in patients with acromegaly (in whom plasma volume is elevated) and might return to normal levels when the disease was treated successfully. We measured the ability of plasma extracts from patients with acromegaly to inhibit the binding of ouabain to the sodium pump in normal red cells and to inhibit the enzymatic activity (sodium-potassium-ATPase) of the sodium pump in membrane preparations from normal kidneys. In 21 patients with active acromegaly, the mean (+/- SE) level of ouabain-binding inhibition (1.56 +/- 0.38) was higher (P less than 0.01) than that in either 11 successfully treated patients (0.18 +/- 0.05) or in 27 normal controls (0.19 +/- 0.03). The inhibition of sodium-potassium-ATPase activity by plasma was also greater in patients with active acromegaly (38.1 +/- 6.8 percent) than in successfully treated patients (18.4 +/- 5.6 percent, P less than 0.05) or controls (21.1 +/- 2.7 percent, P less than 0.05). Significant correlations were found between plasma volume and ouabain-binding inhibition in 23 patients (r = 0.72, P less than 0.01) and sodium-potassium-ATPase inhibition in 19 patients (r = 0.62, P less than 0.01). Pituitary adenomectomy decreased plasma volume and the inhibition by plasma of ouabain binding. We conclude that an endogenous digitalis-like factor is present in the plasma of patients with chronic volume expansion due to acromegaly. These results are consistent with the hypothesis that this natriuretic factor may have a physiologic role in water and sodium homeostasis.
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Kramer HJ, Lichardus B. Atrial natriuretic hormones--thirty years after the discovery of atrial volume receptors. KLINISCHE WOCHENSCHRIFT 1986; 64:719-31. [PMID: 2945041 DOI: 10.1007/bf01734338] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Twenty-five years after the discoveries of the existence of atrial granules and of volume receptors in the heart atria the search for natriuretic hormones has led to the isolation and identification of the atrial natriuretic factors (ANF) now considered as a hormonal system. These peptides are probably synthesized and stored in the Golgi apparatus of cardiac myocytes and are released in response to atrial wall stretch following acute plasma volume expansion and increased central blood volume, e.g., during head-out water immersion, in arterial hypertension, or increased left and/or right atrial pressure in cardiac failure, but also possibly in response to increased frequency of myocardial contractions, e.g. in paroxysmal tachycardia. The mechanisms of the renal action of these potent natriuretic hormones are not yet precisely known. Increased GFR may contribute to the initial rise in urinary sodium excretion and increased renal medullary blood flow to the later phase of natriuresis. The proximal tubule, the thin descending and the ascending limb of Henle's loop and especially the medullary collecting tubule were so far incriminated as tubular sites of action of ANF. Finally, recycling of sodium in medullary tissue and secretion of sodium via back-flux from the interstitium into the medullary collecting tubule are postulated to result in the hypernatric urine observed after ANF administration. Direct suppression of the secretion of renin, aldosterone, vasopressin, and vasopressin-stimulated cAMP synthesis may also contribute to its diuretic, natriuretic, and antihypertensive effects. The renal hemodynamic and tubular as well as the adrenal and systemic vascular effects are related to enhanced cGMP synthesis in medium-sized arterial vessels, in glomeruli and specific tubular segments, and in adrenal tissue, and may be calcium dependent. Specific ANF-binding sites were detected in these target organs. Although increased ANF release was observed in response to atrial distension in various disease states, which may contribute to renal sodium elimination in human hypertension and congestive heart failure, further studies are needed to identify its precise physiological and pathophysiological significance.
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15
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Györy AZ, Beck F, Rick R, Thurau K. Electron microprobe analysis of proximal tubule cellular Na, Cl and K element concentrations during acute mannitol-saline volume expansion in rats: evidence for inhibition of the Na pump. Pflugers Arch 1985; 403:205-9. [PMID: 2580272 DOI: 10.1007/bf00584101] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
It has previously been shown that during mannitol-saline volume expansion (VE) Na transport was inhibited 50% by harvested proximal tubular fluid without a change in paracellular shunt pathway permeability to Na. To determine whether this inhibition was due to changes in cellular entry step or an effect on the pump itself, intracellular element concentrations were measured by electron microprobe X-ray ranalysis in proximal tubular cells of control (non-expanded, NE) and VE rats. Nai, Cli and phosphorusi were increased (mean +/- S.E.) from 19.3 +/- 0.8 to 23.4 +/- 0.6, 15.8 +/- 0.4 to 21.3 +/- 0.4 and 124.3 +/- 2.6 to 138.0 +/- 1.8 mmol . kg-1 wet weight (P less than 0.001) respectively while Ki remained unchanged: 122.9 +/- 2.2 and 124.2 +/- 1.3 mmol . kg-1 wet weight. The increases in Nai and Cli were in excess of cell shrinkage produced by the hyperosmolal peritubular environment while the unchanged Ki in the face of cell shrinkage indicates and actual loss. It is concluded that mannitol-saline VE inhibits the Na pump producing a rise in Nai and a fall in Ki.
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Hamlyn JM, Blaustein MP. Endogenous digitalis-like compounds: putative regulators of the sodium pump. Trends Neurosci 1984. [DOI: 10.1016/s0166-2236(84)80074-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Martin B, Favre H. Natriuretic factor exerts a ouabain-like activity in the rat colon in vitro. Pflugers Arch 1984; 400:300-5. [PMID: 6539464 DOI: 10.1007/bf00581563] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A previously described natriuretic factor (NF) found in urine from man receiving a high salt diet has been postulated to be of hormonal nature. This factor inhibits Na-K ATPase and binds to ouabain receptors. In order to investigate if NF exerts its physiological activity through the Na-K ouabain sensitive pump, its capacity for inhibiting sodium transport has been tested in an in vitro rat colon preparation. Colonic mucosa from rats fed 0.55, 3.55, and 6.55 mmol Na a day were mounted in an Ussing chamber. Inhibition of short-circuit current (SCC) and PD was observed only when NF was added to the serosal side of the membrane and was similar to that observed with ouabain. In rats fed a low or normal salt diet, inhibition of SCC and PD starts after a lag period of 10 min and reaches its maximum inhibition (about 60%) after 90 min. By contrast colonic mucosa from rats receiving a high salt diet exhibits a higher SCC and PD (basal values) and inhibition of the sodium transport starts immediately after addition of NF to the bathing solution. The data demonstrate the similarity of physiological action of ouabain and natriuretic factor on the sodium transport by the colon in vitro. Experiments with rats receiving a high salt diet suggest that by contrast to the kidney, NaCl-dependent cotransport is strongly stimulated by the salt intake in the colon and could be directly inhibited by ouabain or a ouabain-like substance i.e. NF.
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Devynck MA, Pernollet MG, Rosenfeld JB, Meyer P. Measurement of digitalis-like compound in plasma: application in studies of essential hypertension. BMJ 1983; 287:631-4. [PMID: 6309318 PMCID: PMC1548804 DOI: 10.1136/bmj.287.6393.631] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A digitalis-like compound was detected in human plasma by tritiated ouabain competition binding to the sodium pump. The study comprised analyses of plasma extracts from 17 normal controls, 17 normotensive subjects with one or both parents hypertensive, and 16 patients with untreated essential hypertension. In two thirds of the untreated hypertensive and several of the normotensive subjects with a family history of hypertension the potency of the digitalis-like compound, as measured by its interference with ouabain binding, was significantly greater than in the controls. In the untreated hypertensive patients the potency of the compound was significantly correlated with the urinary sodium output. Measurement of this salt-related, digitalis-like compound may be useful in clinical studies of hypertension.
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Abstract
The kinetic characteristics of [3H]-ouabain binding to human lymphocytes and mixtures of mononucleated cells, and the maximum [3H]-ouabain binding capacities of these cells were studied. The [3H]-ouabain binding was compatible with a single class of receptors with a high affinity for the drug. No signs of positive or negative cooperativity could be demonstrated. In six experiments with pure lymphocyte preparations, the association and dissociation rate constants were 3.08 +/- 0.34 X 10(4)/M/S and 1.58 +/- 0.50 X 10(-4)/S. The dissociation constant derived from equilibrium studies on lymphocytes was 0.68 +/- 0.21 X 10(-8) M, which was identical to that of mononucleated cells. In healthy subjects the maximum [3H]-ouabain binding capacities, which reflect the number of sodium/potassium pump sites were 43154 +/- 8037 molecules/cell (n = 25) in lymphocytes and 75474 +/- 6764 (n = 9) molecules/cell in mixtures of mononucleated cells. Direct determination of the [3H]-ouabain binding capacity of lymphocytes can be performed with acceptable accuracy and precision using 30 ml whole blood. Provided high cell purity, this method may be useful, when studying sodium/potassium pump function in clinical settings.
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MacGregor GA, Fenton S, Alaghband-Zadeh J, Markandu N, Roulston JE, de Wardener HE. Evidence for a raised concentration of a circulating sodium transport inhibitor in essential hypertension. BMJ : BRITISH MEDICAL JOURNAL 1981; 283:1355-7. [PMID: 6274473 PMCID: PMC1507779 DOI: 10.1136/bmj.283.6303.1355] [Citation(s) in RCA: 82] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A cytochemical technique that measures the ability of plasma to stimulate guinea-pig renal glucose-6-phosphate dehydrogenase (G6PD) activity in vitro, which is a marker of its ability to inhibit Na+-K+-adenosine-triphosphatase (Na+-K+-ATPase), was used in 19 patients with essential hypertension and 23 normotensive, healthy subjects. The ability of plasma to stimulate G6PD was significantly greater in the hypertensive patients when they were taking their normal sodium diet than in the normotensive subjects, and was significantly correlated with blood pressure. The ability of plasma to stimulate G6PD was inversely correlated with plasma renin activity in the hypertensive patients and increased with age and sodium intake in the normotensive subjects. These results support the hypothesis that essential hypertension, and also perhaps the increase in blood pressure with age in communities that consume large quantities of salt, is in part due to an increase in a circulating concentration of an inhibitor of Na+-N+-ATPase.
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