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Duncker DJ, Sorop O, van de Wouw J, Fen G, de Beer VJ, Taverne YJ, de Graaff HJD, Merkus D. Integrated control of coronary blood flow in exercising swine by adenosine, nitric oxide, and K ATP channels. Am J Physiol Heart Circ Physiol 2022; 323:H1080-H1090. [PMID: 36206049 DOI: 10.1152/ajpheart.00109.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The interplay of mechanisms regulating coronary blood flow (CBF) remains incompletely understood. Previous studies in dogs indicated that CBF regulation by KATP channels, adenosine, and nitric oxide (NO) follows a nonlinear redundancy design and fully accounted for exercise-induced coronary vasodilation. Conversely, in swine, these mechanisms appear to regulate CBF in a linear additive fashion with considerable exercise-induced vasodilation remaining when all three mechanisms are inhibited. A direct comparison between these studies is hampered by the different doses and administration routes (intravenous vs. intracoronary) of drugs inhibiting these mechanisms. Here, we investigated the role of KATP channels, adenosine, and NO in CBF regulation in swine using identical drug regimen as previously employed in dogs. Instrumented swine were exercised on a motor-driven treadmill, before and after blockade of KATP channels (glibenclamide, 50 µg/kg/min ic) and combination of inhibition of NO synthase (Nω-nitro-l-arginine, NLA, 1.5 mg/kg ic) and adenosine receptors (8-phenyltheophylline, 8PT, 5 mg/kg iv) or their combination NLA + 8PT + glibenclamide. Glibenclamide and NLA + 8PT each produced coronary vasoconstriction both at rest and during exercise, whereas the combination of NLA + 8PT + glibenclamide resulted in a small further coronary vasoconstriction compared with NLA + 8PT that was, however, less than the sum of the vasoconstriction produced by NLA + 8PT and glibenclamide, each. Thus, in contrast to previous observations in the dog, 1) the coronary vasoconstrictor effect of glibenclamide was not enhanced in the presence of NLA + 8PT and 2) the exercise-induced increase in CBF was largely maintained. These findings show profound species differences in the mechanisms controlling CBF at rest and during exercise.NEW & NOTEWORTHY The present study demonstrates important species differences in the regulation of coronary blood flow by adenosine, NO, and KATP channels at rest and during exercise. In swine, these mechanisms follow a linear additive design, as opposed to dogs which follow a nonlinear redundant design. Simultaneous blockade of all three mechanisms virtually abolished exercise-induced coronary vasodilation in dogs, whereas a substantial vasodilator reserve could still be recruited during exercise in swine.
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Affiliation(s)
- Dirk J Duncker
- Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Oana Sorop
- Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Jens van de Wouw
- Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Gao Fen
- Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Vincent J de Beer
- Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Yannick J Taverne
- Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Henri J D de Graaff
- Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Daphne Merkus
- Divison of Experimental Cardiology, Department of Cardiology, Thorax Center, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands.,Walter Brendel Center of Experimental Medicine, LMU Munich, Munich, Germany.,German Center for Cardiovascular Research, Partner Site Munich, Munich Heart Alliance, Munich, Germany
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Troy AM, Cheng HM. Human microvascular reactivity: a review of vasomodulating stimuli and non-invasive imaging assessment. Physiol Meas 2021; 42. [PMID: 34325417 DOI: 10.1088/1361-6579/ac18fd] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 07/29/2021] [Indexed: 11/11/2022]
Abstract
The microvasculature serves an imperative function in regulating perfusion and nutrient exchange throughout the body, adaptively altering blood flow to preserve hemodynamic and metabolic homeostasis. Its normal functioning is vital to tissue health, whereas its dysfunction is present in many chronic conditions, including diabetes, heart disease, and cognitive decline. As microvascular dysfunction often appears early in disease progression, its detection can offer early diagnostic information. To detect microvascular dysfunction, one uses imaging to probe the microvasculature's ability to react to a stimulus, also known as microvascular reactivity (MVR). An assessment of MVR requires an integrated understanding of vascular physiology, techniques for stimulating reactivity, and available imaging methods to capture the dynamic response. Practical considerations, including compatibility between the selected stimulus and imaging approach, likewise require attention. In this review, we provide a comprehensive foundation necessary for informed imaging of MVR, with a particular focus on the challenging endeavor of assessing microvascular function in deep tissues.
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Affiliation(s)
- Aaron M Troy
- Institute of Biomedical Engineering, University of Toronto, Toronto, CANADA
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3
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Manoury B, Idres S, Leblais V, Fischmeister R. Ion channels as effectors of cyclic nucleotide pathways: Functional relevance for arterial tone regulation. Pharmacol Ther 2020; 209:107499. [PMID: 32068004 DOI: 10.1016/j.pharmthera.2020.107499] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Accepted: 02/05/2020] [Indexed: 02/07/2023]
Abstract
Numerous mediators and drugs regulate blood flow or arterial pressure by acting on vascular tone, involving cyclic nucleotide intracellular pathways. These signals lead to regulation of several cellular effectors, including ion channels that tune cell membrane potential, Ca2+ influx and vascular tone. The characterization of these vasocontrictive or vasodilating mechanisms has grown in complexity due to i) the variety of ion channels that are expressed in both vascular endothelial and smooth muscle cells, ii) the heterogeneity of responses among the various vascular beds, and iii) the number of molecular mechanisms involved in cyclic nucleotide signalling in health and disease. This review synthesizes key data from literature that highlight ion channels as physiologically relevant effectors of cyclic nucleotide pathways in the vasculature, including the characterization of the molecular mechanisms involved. In smooth muscle cells, cation influx or chloride efflux through ion channels are associated with vasoconstriction, whereas K+ efflux repolarizes the cell membrane potential and mediates vasodilatation. Both categories of ion currents are under the influence of cAMP and cGMP pathways. Evidence that some ion channels are influenced by CN signalling in endothelial cells will also be presented. Emphasis will also be put on recent data touching a variety of determinants such as phosphodiesterases, EPAC and kinase anchoring, that complicate or even challenge former paradigms.
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Affiliation(s)
- Boris Manoury
- Inserm, Umr-S 1180, Université Paris-Saclay, Châtenay-Malabry, France.
| | - Sarah Idres
- Inserm, Umr-S 1180, Université Paris-Saclay, Châtenay-Malabry, France
| | - Véronique Leblais
- Inserm, Umr-S 1180, Université Paris-Saclay, Châtenay-Malabry, France
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4
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Abstract
The heart is uniquely responsible for providing its own blood supply through the coronary circulation. Regulation of coronary blood flow is quite complex and, after over 100 years of dedicated research, is understood to be dictated through multiple mechanisms that include extravascular compressive forces (tissue pressure), coronary perfusion pressure, myogenic, local metabolic, endothelial as well as neural and hormonal influences. While each of these determinants can have profound influence over myocardial perfusion, largely through effects on end-effector ion channels, these mechanisms collectively modulate coronary vascular resistance and act to ensure that the myocardial requirements for oxygen and substrates are adequately provided by the coronary circulation. The purpose of this series of Comprehensive Physiology is to highlight current knowledge regarding the physiologic regulation of coronary blood flow, with emphasis on functional anatomy and the interplay between the physical and biological determinants of myocardial oxygen delivery. © 2017 American Physiological Society. Compr Physiol 7:321-382, 2017.
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Affiliation(s)
- Adam G Goodwill
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN
| | - Gregory M Dick
- California Medical Innovations Institute, 872 Towne Center Drive, Pomona, CA
| | - Alexander M Kiel
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN
- Weldon School of Biomedical Engineering, Purdue University, 206 S Martin Jischke Drive, Lafayette, IN
| | - Johnathan D Tune
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN
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Ellinsworth DC, Sandow SL, Shukla N, Liu Y, Jeremy JY, Gutterman DD. Endothelium-Derived Hyperpolarization and Coronary Vasodilation: Diverse and Integrated Roles of Epoxyeicosatrienoic Acids, Hydrogen Peroxide, and Gap Junctions. Microcirculation 2016; 23:15-32. [PMID: 26541094 DOI: 10.1111/micc.12255] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 11/01/2015] [Indexed: 12/22/2022]
Abstract
Myocardial perfusion and coronary vascular resistance are regulated by signaling metabolites released from the local myocardium that act either directly on the VSMC or indirectly via stimulation of the endothelium. A prominent mechanism of vasodilation is EDH of the arteriolar smooth muscle, with EETs and H(2)O(2) playing important roles in EDH in the coronary microcirculation. In some cases, EETs and H(2)O(2) are released as transferable hyperpolarizing factors (EDHFs) that act directly on the VSMCs. By contrast, EETs and H(2)O(2) can also promote endothelial KCa activity secondary to the amplification of extracellular Ca(2+) influx and Ca(2+) mobilization from intracellular stores, respectively. The resulting endothelial hyperpolarization may subsequently conduct to the media via myoendothelial gap junctions or potentially lead to the release of a chemically distinct factor(s). Furthermore, in human isolated coronary arterioles dilator signaling involving EETs and H(2)O(2) may be integrated, being either complimentary or inhibitory depending on the stimulus. With an emphasis on the human coronary microcirculation, this review addresses the diverse and integrated mechanisms by which EETs and H(2)O(2) regulate vessel tone and also examines the hypothesis that myoendothelial microdomain signaling facilitates EDH activity in the human heart.
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Affiliation(s)
| | - Shaun L Sandow
- Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore, Queensland, Australia
| | - Nilima Shukla
- Bristol Heart Institute, University of Bristol, Bristol, UK
| | - Yanping Liu
- Division of Research Infrastructure, National Center for Research Resources, National Institutes of Health, Bethesda, Maryland, USA
| | - Jamie Y Jeremy
- Bristol Heart Institute, University of Bristol, Bristol, UK
| | - David D Gutterman
- Division of Cardiovascular Medicine, Departments of Medicine, Physiology and Pharmacology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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6
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Dokken BB, Piermarini CV, Teachey MK, Gura MT, Dameff CJ, Heller BD, Krate J, Ashgar AM, Querin L, Mitchell JL, Hilwig RW, Kern KB. Glucagon-like peptide-1 preserves coronary microvascular endothelial function after cardiac arrest and resuscitation: potential antioxidant effects. Am J Physiol Heart Circ Physiol 2012; 304:H538-46. [PMID: 23241323 DOI: 10.1152/ajpheart.00282.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) has protective effects in the heart. We hypothesized that GLP-1 would mitigate coronary microvascular and left ventricular (LV) dysfunction if administered after cardiac arrest and resuscitation (CAR). Eighteen swine were subjected to ventricular fibrillation followed by resuscitation. Swine surviving to return of spontaneous circulation (ROSC) were randomized to receive an intravenous infusion of either human rGLP-1 (10 pmol·kg(-1)·min(-1); n = 8) or 0.9% saline (n = 8) for 4 h, beginning 1 min after ROSC. CAR caused a decline in coronary flow reserve (CFR) in control animals (pre-arrest, 1.86 ± 0.20; 1 h post-ROSC, 1.3 ± 0.05; 4 h post-ROSC, 1.25 ± 0.06; P < 0.05). GLP-1 preserved CFR for up to 4 h after ROSC (pre-arrest, 1.31 ± 0.17; 1 h post-ROSC, 1.5 ± 0.01; 4 h post-ROSC, 1.55 ± 0.22). Although there was a trend toward improvement in LV relaxation in the GLP-1-treated animals, overall LV function was not consistently different between groups. 8-iso-PGF(2α), a measure of reactive oxygen species load, was decreased in post-ROSC GLP-1-treated animals [placebo, control (NS): 38.1 ± 1.54 pg/ml; GLP-1: 26.59 ± 1.56 pg/ml; P < 0.05]. Infusion of GLP-1 after CAR preserved coronary microvascular and LV diastolic function. These effects may be mediated through a reduction in oxidative stress.
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Affiliation(s)
- Betsy B Dokken
- Department of Medicine, University of Arizona, Tucson, AZ, USA.
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Félétou M. The Endothelium, Part I: Multiple Functions of the Endothelial Cells -- Focus on Endothelium-Derived Vasoactive Mediators. ACTA ACUST UNITED AC 2011. [DOI: 10.4199/c00031ed1v01y201105isp019] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Edwards G, Félétou M, Weston AH. Endothelium-derived hyperpolarising factors and associated pathways: a synopsis. Pflugers Arch 2010; 459:863-79. [PMID: 20383718 DOI: 10.1007/s00424-010-0817-1] [Citation(s) in RCA: 279] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 02/22/2010] [Accepted: 02/24/2010] [Indexed: 12/29/2022]
Abstract
The term endothelium-derived hyperpolarising factor (EDHF) was introduced in 1987 to describe the hypothetical factor responsible for myocyte hyperpolarisations not associated with nitric oxide (EDRF) or prostacyclin. Two broad categories of EDHF response exist. The classical EDHF pathway is blocked by apamin plus TRAM-34 but not by apamin plus iberiotoxin and is associated with endothelial cell hyperpolarisation. This follows an increase in intracellular [Ca(2+)] and the opening of endothelial SK(Ca) and IK(Ca) channels preferentially located in caveolae and in endothelial cell projections through the internal elastic lamina, respectively. In some vessels, endothelial hyperpolarisations are transmitted to myocytes through myoendothelial gap junctions without involving any EDHF. In others, the K(+) that effluxes through SK(Ca) activates myocytic and endothelial Ba(2+)-sensitive K(IR) channels leading to myocyte hyperpolarisation. K(+) effluxing through IK(Ca) activates ouabain-sensitive Na(+)/K(+)-ATPases generating further myocyte hyperpolarisation. For the classical pathway, the hyperpolarising "factor" involved is the K(+) that effluxes through endothelial K(Ca) channels. During vessel contraction, K(+) efflux through activated myocyte BK(Ca) channels generates intravascular K(+) clouds. These compromise activation of Na(+)/K(+)-ATPases and K(IR) channels by endothelium-derived K(+) and increase the importance of gap junctional electrical coupling in myocyte hyperpolarisations. The second category of EDHF pathway does not require endothelial hyperpolarisation. It involves the endothelial release of factors that include NO, HNO, H(2)O(2) and vasoactive peptides as well as prostacyclin and epoxyeicosatrienoic acids. These hyperpolarise myocytes by opening various populations of myocyte potassium channels, but predominantly BK(Ca) and/or K(ATP), which are sensitive to blockade by iberiotoxin or glibenclamide, respectively.
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Affiliation(s)
- Gillian Edwards
- Faculty of Life Sciences, University of Manchester, CTF Building, 46 Grafton St, Manchester, M13 9NT, UK
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10
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Dick GM, Tune JD. Role of potassium channels in coronary vasodilation. Exp Biol Med (Maywood) 2010; 235:10-22. [DOI: 10.1258/ebm.2009.009201] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
K+ channels in coronary arterial smooth muscle cells (CASMC) determine the resting membrane potential ( Em) and serve as targets of endogenous and therapeutic vasodilators. Em in CASMC is in the voltage range for activation of L-type Ca2+ channels; therefore, when K+ channel activity changes, Ca2+ influx and arterial tone change. This is why both Ca2+ channel blockers and K+ channel openers have such profound effects on coronary blood flow; the former directly inhibits Ca2+ influx through L-type Ca2+ channels, while the latter indirectly inhibits Ca2+ influx by hyperpolarizing Em and reducing Ca2+ channel activity. K+ channels in CASMC play important roles in vasodilation to endothelial, ischemic and metabolic stimuli. The purpose of this article is to review the types of K+ channels expressed in CASMC, discuss the regulation of their activity by physiological mechanisms and examine impairments related to cardiovascular disease.
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Affiliation(s)
- Gregory M Dick
- Department of Exercise Physiology and Center for Cardiovascular & Respiratory Sciences, West Virginia University School of Medicine, Morgantown, WV 26506
| | - Johnathan D Tune
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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11
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Borbouse L, Dick GM, Asano S, Bender SB, Dincer UD, Payne GA, Neeb ZP, Bratz IN, Sturek M, Tune JD. Impaired function of coronary BK(Ca) channels in metabolic syndrome. Am J Physiol Heart Circ Physiol 2009; 297:H1629-37. [PMID: 19749164 DOI: 10.1152/ajpheart.00466.2009] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The role of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels in regulation of coronary microvascular function is widely appreciated, but molecular and functional changes underlying the deleterious influence of metabolic syndrome (MetS) have not been determined. Male Ossabaw miniature swine consumed for 3-6 mo a normal diet (11% kcal from fat) or an excess-calorie atherogenic diet that induces MetS (45% kcal from fat, 2% cholesterol, 20% kcal from fructose). MetS significantly impaired coronary vasodilation to the BK(Ca) opener NS-1619 in vivo (30-100 microg) and reduced the contribution of these channels to adenosine-induced microvascular vasodilation in vitro (1-100 microM). MetS reduced whole cell penitrem A (1 microM)-sensitive K(+) current and NS-1619-activated (10 microM) current in isolated coronary vascular smooth muscle cells. MetS increased the concentration of free intracellular Ca(2+) and augmented coronary vasoconstriction to the L-type Ca(2+) channel agonist BAY K 8644 (10 pM-10 nM). BK(Ca) channel alpha and beta(1) protein expression was increased in coronary arteries from MetS swine. Coronary vascular dysfunction in MetS is related to impaired BK(Ca) channel function and is accompanied by significant increases in L-type Ca(2+) channel-mediated coronary vasoconstriction.
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Affiliation(s)
- Léna Borbouse
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana
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12
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Young EJ, Hill MA, Wiehler WB, Triggle CR, Reid JJ. Reduced EDHF responses and connexin activity in mesenteric arteries from the insulin-resistant obese Zucker rat. Diabetologia 2008; 51:872-81. [PMID: 18324386 DOI: 10.1007/s00125-008-0934-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 12/17/2007] [Indexed: 01/18/2023]
Abstract
AIMS/HYPOTHESIS The objective of this study was to examine the effect of insulin resistance on endothelium-derived hyperpolarising factor (EDHF) and small mesenteric artery endothelial function using 25-week-old insulin-resistant obese Zucker rats (OZRs) and lean littermate control rats (LZRs). The involvement of gap junctions and their connexin subunits in the EDHF relaxation response was also assessed. METHODS Mesenteric arteries were evaluated using the following assays: (1) endothelial function by pressure myography, with internal diameter recorded using video microscopy; (2) connexin protein levels by western blotting; and (3) Cx mRNA expression by real-time PCR. RESULTS Relaxations in response to acetylcholine were significantly smaller in mesenteric arteries from the OZRs than the LZRs, whereas there was no difference in relaxations in response to levcromakalim. Responses to acetylcholine were not altered by nitric oxide inhibitors, but were abolished by charybdotoxin in combination with apamin, which blocked the EDHF component of the response. 40Gap27 significantly attenuated the response to acetylcholine in the LZRs, but had no effect in the OZRs. Connexin 40 protein and Cx40 mRNA levels in mesenteric vascular homogenates were significantly smaller in the OZRs than in the LZRs, with no difference in connexin 43 or Cx43 mRNA levels. CONCLUSIONS/INTERPRETATION These findings demonstrate that endothelial dysfunction in mesenteric arteries from the insulin-resistant OZRs can be attributed to a defect in EDHF. The results also suggest that the defective EDHF is at least partly related to an impairment of connexin 40-associated gap junctions, through a decrease in connexin 40 protein and Cx40 mRNA expression in the OZRs.
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Affiliation(s)
- E J Young
- School of Medical Sciences, RMIT University, Melbourne, Victoria, Australia.
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Pasgaard T, Stankevicius E, Jørgensen MM, Ostergaard L, Simonsen U, Frøbert O. Hyperoxia reduces basal release of nitric oxide and contracts porcine coronary arteries. Acta Physiol (Oxf) 2007; 191:285-96. [PMID: 17784906 DOI: 10.1111/j.1748-1716.2007.01745.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM The purpose of the present study was to investigate whether changes in nitric oxide (NO) concentration is involved in hyperoxia-induced vasoconstriction in porcine conduit coronary arteries. METHODS The effect of hyperoxia on NO release and vasoconstriction was evaluated by tension recording, microsensor measurements, and immunoblotting in porcine conduit coronary arteries contracted with U46619 or 5-hydroxytryptamine. RESULTS In endothelium-intact segments exchanging 20% O2, 5% CO2, 75% N2 (normoxia) for 95% O2, 5% CO2 (hyperoxia) increased contraction. In segments without endothelium hyperoxia-evoked contraction was abolished, but restored by an encircling donor segment with endothelium. An inhibitor of NOS, asymmetric dimethylarginine (ADMA, 300 mum), reduced hyperoxic contraction and basal NO concentration by, respectively, 38 +/- 12% and 46 +/- 3% (P < 0.05, n = 9). A NO donor, S-nitroso-N-acetylpenicillamine (SNAP), increased NO concentration and evoked relaxation to the same levels in normoxic and hyperoxic conditions. beta-actin and endothelial NO synthase (eNOS) protein expression was similar in normoxic and hyperoxic arterial segments. Phosphorylation of eNOS was unaltered in normoxia vs. hyperoxia, but phosphorylation of eNOS-Ser(1177) was increased and phosphorylation of eNOS-Thr(495) decreased by U46619. Blockers of ATP-sensitive, voltage-dependent and calcium-activated K+ channels did not change hyperoxic contraction. However, high extracellular K+ concentration or a second and third exposure to hyperoxia decreased contraction. CONCLUSION The present study provides direct evidence that hyperoxia reduces basal release of NO leading to depletable endothelium-dependent vasoconstriction in porcine coronary arteries independent of changes in eNOS phosphorylation.
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Affiliation(s)
- T Pasgaard
- Department of Pharmacology, University of Aarhus, Aarhus C, Denmark
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14
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Guan BC, Si JQ, Jiang ZG. Blockade of gap junction coupling by glycyrrhetinic acids in guinea pig cochlear artery: a whole-cell voltage- and current-clamp study. Br J Pharmacol 2007; 151:1049-60. [PMID: 17572704 PMCID: PMC2042944 DOI: 10.1038/sj.bjp.0707244] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2006] [Revised: 02/12/2007] [Accepted: 02/16/2007] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Glycyrrhetinic acids (GAs) are widely used as gap junction blockers, but their efficacy and side effects have not been well determined. EXPERIMENTAL APPROACH Whole-cell electrical recordings were made from vascular smooth muscle cells (VSMCs) embedded in or dissociated from, guinea pig cochlear artery segments. KEY RESULTS 18beta- & 18alpha-GA concentration-dependently increased membrane input resistance (R(in)) of in situ VSMCs, with a maximal input conductance (G(in)=1/R(in)) reduction of 92% & 77% and IC(50) of 2.0 & 4.4 microm, respectively. 18betaGA (30 microM) resulted in a R(in) of 2.2 GOmega and C(in) of 12 pF, comparable to those of freshly dissociated VSMCs (3.1 GOmega & 6.1 pF). The GAs (> or =30 microM) caused a depolarization in VSMCs in situ. In dispersed VSMCs, they both inhibited delayed rectifiers; 18betaGA also activated a non-selective cation conductance while 18alphaGA inactivated a voltage-independent K+-conductance. ACh induced an outward current in VSMCs in situ at -40 mV, with a positive slope I/V relation and a reversal potential near E(K). The ACh-induced current was attenuated by 18beta- & 18alphaGA with an IC(50) of 4.3 & 7.8 microM, respectively. CONCLUSIONS AND IMPLICATIONS 18betaGA blocked the vascular gap junctions, achieving a complete electrical isolation of the recorded VSMC at > or =30 microM while causing a mild depolarization by a complex conductance alteration. 18betaGA suppressed the ACh-induced current in VSMC by blocking the myoendothelial gap junction and by a non-junctional action. 18alphaGA at 30-100 microM failed to fully block the gap junctions while exerting side actions.
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Affiliation(s)
- B-C Guan
- Department of Otolaryngology, Oregon Hearing Research Center, Oregon Health and Science University Portland, OR, USA
| | - J-Q Si
- Department of Otolaryngology, Oregon Hearing Research Center, Oregon Health and Science University Portland, OR, USA
- Department of Physiology, Shihezi University Medical College Shihezi, Xinjiang, PR China
| | - Z-G Jiang
- Department of Otolaryngology, Oregon Hearing Research Center, Oregon Health and Science University Portland, OR, USA
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15
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Long Y, Fu CY, Tian XZ, Chen J, Han M, Wang R. Mechanisms of relaxing response induced by rat/mouse hemokinin-1 in porcine coronary arteries: roles of potassium ion and nitric oxide. Eur J Pharmacol 2007; 569:119-25. [PMID: 17560993 DOI: 10.1016/j.ejphar.2007.04.049] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 04/24/2007] [Accepted: 04/25/2007] [Indexed: 11/16/2022]
Abstract
Rat and mouse hemokinin-1(r/m hemokinin-1) is a recently described member of the tachykinin family whose cardiovascular functions are not fully understood. In this study, we investigated the mechanisms of the relaxing response induced by r/m hemokinin-1 in isolated porcine coronary arteries by using a specific antagonist of tachykinin NK(1) receptor (SR140333), a nitric oxide synthase inhibitor N(omega)-nitro-L-arginine (L-NNA), and 1H-[1,2,4] Oxadiazolo [4,3-a] quinoxalin-1-one (ODQ), a blocker of cGMP production. r/m Hemokinin-1 (10(-12)-10(-6 )M) evoked a marked endothelium-dependent vasodilatation (E(max)=121.12+/-10.6% and 91.79+/-2.39% in 10(-6) M PGF(2)alpha and 30 mM KCl precontracted arterial rings, respectively) of coronary arteries mediated by activation of endothelial tachykinin NK(1) receptors. Two components contributed to this r/m hemokinin-1-elicited vasodilatation, the first of which was endothelium-derived hyperpolarizing factor (EDHF), which played a major role. This EDHF was identified as a potassium current through certain kinds of potassium channels on the endothelial cell membrane of porcine coronary arteries. Specific antagonists of Ca(2+)-activated K(+) channels (dequalinium and clotrimazole) did not have an inhibitory effect on the r/m hemokinin-1-induced vasodilatation, whereas they did on the substance P-induced vasodilatation. When potassium ion efflux was impaired by a high K(+) concentration (30 mM) or removal of K(+) from the surroundings, NO synthesis was triggered by r/m hemokinin-1 to produce an equivalent EDHF (K(+))-independent vasorelaxation as a compensatory mechanism.
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Affiliation(s)
- Yuan Long
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Institute of Biochemistry and Molecular Biology, Lanzhou University, 222 Tianshui South Road, Lanzhou, 730000, PR China
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16
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Abstract
The endothelium controls vascular tone not only by releasing nitric oxide (NO) and prostacyclin but also by other pathways causing hyperpolarization of the underlying smooth muscle cells. This characteristic was at the origin of the denomination endothelium-derived hyperpolarizing factor (EDHF). We know now that this acronym includes different mechanisms. In general, EDHF-mediated responses involve an increase in the intracellular calcium concentration, the opening of calcium-activated potassium channels of small and intermediate conductance and the hyperpolarization of the endothelial cells. This results in an endothelium-dependent hyperpolarization of the smooth muscle cells, which can be evoked by direct electrical coupling through myo-endothelial junctions and/or the accumulation of potassium ions in the intercellular space. Potassium ions hyperpolarize the smooth muscle cells by activating inward rectifying potassium channels and/or Na+/K(+)-ATPase. In some blood vessels, including large and small coronary arteries, the endothelium releases arachidonic acid metabolites derived from cytochrome P450 monooxygenases. The epoxyeicosatrienoic acids (EET) generated are not only intracellular messengers but also can diffuse and hyperpolarize the smooth muscle cells by activating large conductance calcium-activated potassium channels. Additionally, the endothelium can produce other factors such as lipoxygenases derivatives or hydrogen peroxide (H2O2). These different mechanisms are not necessarily exclusive and can occur simultaneously.
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Affiliation(s)
- Michel Félétou
- Department of Angiology, Institut de Recherches Servier, Suresnes, France
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Zhang RZ, Yang Q, Yim APC, Huang Y, He GW. Role of NO and EDHF-mediated endothelial function in the porcine pulmonary circulation: Comparison between pulmonary artery and vein. Vascul Pharmacol 2006; 44:183-91. [PMID: 16448859 DOI: 10.1016/j.vph.2005.11.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Revised: 11/11/2005] [Accepted: 11/30/2005] [Indexed: 12/01/2022]
Abstract
OBJECTIVE To compare electrophysiological measurement of nitric oxide (NO) release and endothelium-derived hyperpolarizing factor (EDHF)-mediated endothelial function in porcine pulmonary arteries and veins. METHODS Isolated pulmonary interlobular arteries (PA) and veins (PV) were obtained from a local slaughterhouse. By using a NO-specific electrode and a conventional intracellular microelectrode, the amount of NO released from endothelial cells and hyperpolarization of smooth muscle cells were investigated. The bradykinin (BK)-induced relaxation in the precontraction by U(46619) was examined in the absence or presence of N(G)-nitro-l-arginine (l-NNA), indomethacin (INDO) plus oxyhemoglobin (HbO). RESULTS The basal release of NO was 7.0+/-1.2 nmol/L in PA (n=8) and 5.5+/-1.6 nmol/L in PV (n=8, p<0.01). BK-induced release of NO was 160.4+/-10.3 nmol/L in PA (n=8) and 103.0+/-14.7 nmol/L in PV (n=8, p<0.001) with longer releasing duration in PA than in PV (14.3+/-1.3 vs. 12.1+/-0.8 min, p<0.01). BK evoked an endothelium-dependent hyperpolarization and relaxation that were reduced by l-NNA, INDO, and HbO (hyperpolarization: 12.8+/-1.3 vs. 8.0+/-1.4 mV in PA, n=6, p<0.001 and 8.3+/-1.4 vs. 3.0+/-0.8 mV in PV, n=6, p<0.001; relaxation: 92.8+/-3.1% vs. 19.6+/-11.1% in PA n=8, p<0.001 and 70.3+/-7.9% vs. 6.0+/-6.8% in PV, n=8, p<0.001). Both hyperpolarization (8.0+/-1.4 vs. 3.0+/-0.8 mV, p<0.001) and relaxation (19.6+/-11.1% vs. 6.0+/-6.8%, p<0.01) were greater in PA than in PV. CONCLUSIONS Both NO and EDHF play an important role in regulation of porcine pulmonary arterial and venous tones. The more significant role of NO and EDHF is revealed in pulmonary arteries than in veins.
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Affiliation(s)
- Rong-Zhen Zhang
- Department of Surgery, The Chinese University of Hong Kong, Block B, Prince of Wales Hospital, Shatin, N.T., Hong Kong SAR, China
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18
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Burnham MP, Johnson IT, Weston AH. Reduced Ca2+-dependent activation of large-conductance Ca2+-activated K+ channels from arteries of Type 2 diabetic Zucker diabetic fatty rats. Am J Physiol Heart Circ Physiol 2005; 290:H1520-7. [PMID: 16272200 DOI: 10.1152/ajpheart.00827.2005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although it is well established that diabetes impairs endothelium-dependent vasodilation, including those pathways involving vascular myocyte large-conductance Ca(2+)-activated K(+) channels (BK(Ca)), little is known about the effects of diabetes on BK(Ca) activation as an intrinsic response to contractile stimulation. We have investigated this mechanism in a model of Type 2 diabetes, the male Zucker diabetic fatty (ZDF) rat. BK(Ca) function in prediabetic (5-7 wk) and diabetic (17-20 wk) ZDF and lean control animals was assessed in whole arteries using myograph and electrophysiology techniques and in freshly dissociated myocytes by patch clamping. Log EC(25) values for phenylephrine concentration-tension curves were shifted significantly to the left by blockade of BK(Ca) with iberiotoxin (IBTX) in arteries from non- and prediabetic animals but not from diabetic animals. Smooth muscle hyperpolarizations of arteries evoked by the BK(Ca) opener NS-1619 were significantly reduced in the diabetic group. Voltage-clamp recordings indicated that IBTX-sensitive currents were not enhanced to the extent observed in nondiabetic controls by increasing the Ca(2+) concentration in the pipette solution or the application of NS-1619 in myocytes from diabetic animals. An alteration in the expression of BK(Ca) beta(1) subunits was not evident at either the mRNA or protein level in arteries from diabetic animals. Collectively, these results suggest that myocyte BK(Ca) of diabetic animals does not significantly oppose vasoconstriction, unlike that of prediabetic and control animals. This altered function was related to a reduced Ca(2+)-dependent activation of the channel not involving beta(1) subunits.
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Affiliation(s)
- Matthew P Burnham
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
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Weston AH, Félétou M, Vanhoutte PM, Falck JR, Campbell WB, Edwards G. Bradykinin-induced, endothelium-dependent responses in porcine coronary arteries: involvement of potassium channel activation and epoxyeicosatrienoic acids. Br J Pharmacol 2005; 145:775-84. [PMID: 15895105 PMCID: PMC1576199 DOI: 10.1038/sj.bjp.0706256] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
In coronary arteries, bradykinin opens endothelial intermediate- and small-conductance Ca2+-sensitive K+ channels (IK(Ca) and SK(Ca)) and, additionally, releases epoxyeicosatrienoic acids (EETs) from the endothelium. To clarify the involvement of these pathways in endothelium-dependent myocyte hyperpolarization, bradykinin-induced electrical changes in endothelial cells and myocytes of porcine coronary arteries (following nitric oxide (NO) synthase and cyclooxygenase inhibition) were measured using sharp microelectrodes. Hyperpolarization of endothelial cells by bradykinin (27.0 +/- 0.9 mV, n = 4) was partially inhibited (74%) by blockade of IK(Ca) and SK(Ca) channels using 10 microM TRAM-39 (2-(2-chlorophenyl)-2,2-diphenylacetonitrile) plus 100 nM apamin (leaving an iberiotoxin-sensitive component), whereas the response to substance P was abolished. After gap junction blockade with HEPES, (N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulphonic acid)) hyperpolarization of the endothelium by 100 nM bradykinin was abolished by TRAM-39 plus apamin, whereas myocyte hyperpolarization still occurred (12.9 +/- 1.0 mV, n=4). The residual hyperpolarizations to 100 nM bradykinin were antagonized by the EET antagonist, 14,15-EEZE (14,15-epoxyeicosa-5(Z)-enoic acid) (10 microM), and abolished by iberiotoxin. Bradykinin-induced myocyte hyperpolarizations were also reduced by 14,15-EEZE-mSI (14,15-EEZE-methylsulfonylimide) (5,6- and 14,15-EET antagonist), whereas those to exogenous 11,12-EET were unaffected. These data show that bradykinin-induced hyperpolarization of endothelial cells (due to the opening of IK(Ca) and SK(Ca) channels) is electrotonically transferred to the myocytes via gap junctions. Bradykinin (but not substance P) also hyperpolarizes myocytes by a mechanism (independent of endothelial cell hyperpolarization) which involves endothelial cell production of EETs (most likely 14,15- and/or 11,12-EET). These open endothelial IK(Ca) and SK(Ca) channels and also activate large-conductance calcium-sensitive K+ channels (BK(Ca)) on the surrounding myocytes.
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Affiliation(s)
- Arthur H Weston
- Faculty of Life Sciences, University of Manchester, G38 Stopford Building, Manchester M13 9PT
| | - Michel Félétou
- Départment de Diabétologie, Institut de Recherche Servier, 92150 Suresnes, France
| | - Paul M Vanhoutte
- Department of Pharmacology, University of Hong Kong, Faculty of Medicine Building, Hong Kong, China
| | - John R Falck
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, U.S.A
| | - William B Campbell
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, U.S.A
| | - Gillian Edwards
- Faculty of Life Sciences, University of Manchester, G38 Stopford Building, Manchester M13 9PT
- Author for correspondence:
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Batenburg WW, Tom B, Schuijt MP, Danser AHJ. Angiotensin II type 2 receptor-mediated vasodilation. Focus on bradykinin, NO and endothelium-derived hyperpolarizing factor(s). Vascul Pharmacol 2005; 42:109-18. [PMID: 15792928 DOI: 10.1016/j.vph.2005.01.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Angiotensin (Ang) II type 1 (AT(1)) receptors account for the majority of the cardiovascular effects Ang II, including vasoconstriction and growth stimulation. Recent evidence, mainly obtained in animals, suggests that Ang II type 2 (AT(2)) receptors counteract some or all of these effects. This review summarizes the current knowledge on the vasodilator effects induced by AT(2) receptors in humans and animals, focussing not only on the mediators of this effect, but also on the modulatory role of age, gender, and endothelial function. It is concluded that AT(2) receptor-mediated vasodilation most likely depends on the bradykinin-bradykinin type 2 (B(2)) receptor-NO-cGMP pathway, although evidence for a direct link between AT(2) and B(2) receptors is currently lacking. If indeed B(2) receptors are involved, this would imply that, in addition to NO, also the wide range of non-NO 'endothelium-derived hyperpolarizing factors' (EDHFs) that is released following B(2) receptor activation (e.g., K(+), cytochrome P450 products from arachidonic acid, H(2)O(2) and S-nitrososothiols), could contribute to AT(2) receptor-induced vasodilation.
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Affiliation(s)
- Wendy W Batenburg
- Department of Pharmacology, room EE1418b, Erasmus MC, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands
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Weston AH, Absi M, Ward DT, Ohanian J, Dodd RH, Dauban P, Petrel C, Ruat M, Edwards G. Evidence in favor of a calcium-sensing receptor in arterial endothelial cells: studies with calindol and Calhex 231. Circ Res 2005; 97:391-8. [PMID: 16037572 DOI: 10.1161/01.res.0000178787.59594.a0] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Small increases in extracellular Ca2+ dilate isolated blood vessels. In the present study, the possibility that a vascular, extracellular Ca2+-sensing receptor (CaSR) could mediate these vasodilator actions was investigated. Novel ligands that interact with the CaSR were used in microelectrode recordings from rat isolated mesenteric and porcine coronary arteries. The major findings were that (1) raising extracellular Ca2+ or adding calindol, a CaSR agonist, produced concentration-dependent hyperpolarizations of vascular myocytes, actions attenuated by Calhex 231, a negative allosteric modulator of CaSR. (2) Calindol-induced hyperpolarizations were inhibited by the intermediate conductance, Ca2+-sensitive K+ (IKCa) channel inhibitors, TRAM-34, and TRAM-39. (3) The effects of calindol were not observed in the absence of endothelium. (4) CaSR mRNA and protein were present in rat mesenteric arteries and in porcine coronary artery endothelial cells. (5) CaSR and IKCa proteins were restricted to caveolin-poor membrane fractions. We conclude that activation of vascular endothelial CaSRs opens endothelial cell IKCa channels with subsequent myocyte hyperpolarization. The endothelial cell CaSR may have a physiological role in the control of arterial blood pressure.
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Gluais P, Edwards G, Weston AH, Falck JR, Vanhoutte PM, Félétou M. Role of SK(Ca) and IK(Ca) in endothelium-dependent hyperpolarizations of the guinea-pig isolated carotid artery. Br J Pharmacol 2005; 144:477-85. [PMID: 15655533 PMCID: PMC1576024 DOI: 10.1038/sj.bjp.0706003] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. This study was designed to determine whether the endothelium-dependent hyperpolarizations evoked by acetylcholine in guinea-pig carotid artery involve a cytochrome P450 metabolite and whether they are linked to the activation of two distinct populations of endothelial K(Ca) channels, SK(Ca) and IK(Ca.) 2. The membrane potential was recorded in the vascular smooth muscle cells of the guinea-pig isolated carotid artery. All the experiments were performed in the presence of N(omega)-L-nitro arginine (100 microM) and indomethacin (5 microM). 3. Under control conditions (Ca(2+): 2.5 mM), acetylcholine (10 nM to 10 muM) induced a concentration- and endothelium-dependent hyperpolarization of the vascular smooth muscle cells. Two structurally different specific blockers of SK(Ca), apamin (0.5 microM) or UCL 1684 (10 microM), produced a partial but significant inhibition of the hyperpolarization evoked by acetylcholine whereas charybdotoxin (0.1 microM) and TRAM-34 (10 microM), a nonpeptidic and specific blocker of IK(Ca), were ineffective. In contrast, the combinations of apamin plus charybdotoxin, apamin plus TRAM-34 (10 microM) or UCL 1684 (10 microM) plus TRAM-34 (10 microM) virtually abolished the acetylcholine-induced hyperpolarization. 4. In the presence of a combination of apamin and a subeffective dose of TRAM-34 (5 microM), the residual hyperpolarization produced by acetylcholine was not inhibited further by the addition of either an epoxyeicosatrienoic acid antagonist, 14,15-EEZE (10 microM) or the specific blocker of BK(Ca), iberiotoxin (0.1 microM). 5. In presence of 0.5 mM Ca(2+), the hyperpolarization in response to acetylcholine (1 microM) was significantly lower than in 2.5 mM Ca(2+). The EDHF-mediated responses became predominantly sensitive to charybdotoxin or TRAM-34 but resistant to apamin. 6. This investigation shows that the production of a cytochrome P450 metabolite, and the subsequent activation of BK(Ca), is unlikely to contribute to the EDHF-mediated responses in the guinea-pig carotid artery. Furthermore, the EDHF-mediated response involves the activation of both endothelial IK(Ca) and SK(Ca) channels, the activation of either one being able to produce a true hyperpolarization.
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MESH Headings
- Acetylcholine/pharmacology
- Animals
- Calcium/pharmacology
- Carotid Artery, Internal/cytology
- Carotid Artery, Internal/metabolism
- Carotid Artery, Internal/physiology
- Dose-Response Relationship, Drug
- Endothelium, Vascular/cytology
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/physiology
- Guinea Pigs
- In Vitro Techniques
- Male
- Membrane Potentials/physiology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/physiology
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Calcium-Activated/metabolism
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Affiliation(s)
| | | | | | - John R Falck
- Department of Biochemistry, University of Texas, Dallas, U.S.A
| | - Paul M Vanhoutte
- Department of Pharmacology, Faculty of Medicine, Hong Kong, China
| | - Michel Félétou
- Institut de Recherches Servier, Suresnes, France
- Author for correspondence:
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23
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Abstract
1. The principal mediators of vascular tone are neural, endothelial and physical stimuli that result in the initiation of dilator and constrictor responses to facilitate the control of blood pressure. Two primary vasodilatory stimuli produced by the endothelium are nitric oxide (NO) and prostaglandins. An additional endothelium-dependent vasodilatory mechanism is characterized as the hyperpolarization-mediated relaxation that remains after the inhibition of the synthesis of NO and prostaglandins. This mechanism is due to the action of a so-called endothelium-derived hyperpolarizing factor (EDHF) and is dependent on either the release of diffusible factor(s) and/or to a direct contact-mediated mechanism. 2. Most evidence supports the concept that 'EDHF' activity is dependent on contact-mediated mechanisms. This involves the transfer of an endothelium-derived electrical current, as an endothelium-derived hyperpolarization (EDH), through direct heterocellular coupling of endothelial cells and smooth muscle cells via myoendothelial gap junctions (MEGJ). However, there is a lack of consensus with regard to the nature and mechanism of action of EDHF/EDH (EDH(F)), which has been shown to vary within and between vascular beds, as well as among species, strains, sex and during development, ageing and disease. 3. In addition to actual heterogeneity in EDH(F), further heterogeneity has resulted from the less-than-optimal design, analysis and interpretation of data in some key papers in the EDHF literature; with such views being perpetuated in the subsequent literature. 4. The focus of the present brief review is to examine what factors are proposed as EDH(F) and highlight the correlative structural and functional studies from our laboratory that demonstrate an integral role for MEGJ in the conduction of EDH, which account for the heterogeneity in EDH(F), while incorporating the reported diffusible mechanisms in the regulation of this activity. Furthermore, in addition to the reported heterogeneity in the nature and mechanism of action of EDH(F), the contribution of experimental design and technique to this heterogeneity will be examined.
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Affiliation(s)
- Shaun L Sandow
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia.
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Batenburg WW, de Vries R, Saxena PR, Danser AHJ. L-S-nitrosothiols: endothelium-derived hyperpolarizing factors in porcine coronary arteries? J Hypertens 2005; 22:1927-36. [PMID: 15361764 DOI: 10.1097/00004872-200410000-00015] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Bradykinin-induced, endothelium-derived hyperpolarizing factor (EDHF)-mediated responses depend on Ca-dependent K-channels (KCa) of small (SKCa) and intermediate (IKCa) conductance, inwardly rectifying K (KIR) channels and/or Na-K-ATPase. Here we investigated in porcine coronary arteries (PCAs) whether S-nitrosothiols can act as EDHF. METHODS Preconstricted PCAs were exposed to bradykinin, the NO donor S-nitroso-N-penicillamine (SNAP), or the S-nitrosothiols L-S-nitrosocysteine (L-SNC), D-SNC and L-S-nitrosoglutathione (L-SNG), with or without KCl, the NO scavenger hydroxocobalamin, the S-nitrosothiol-depleting agent p-hydroxymercurobenzoic acid (PHMBA) and/or inhibitors of NO synthase (L-NAME), guanylyl cyclase (ODQ), SKCa channels (apamin), KCa channels of large conductance (BKCa) (iberiotoxin), IKCa + BKCa channels (charybdotoxin), KIR channels (BaCl2) or Na-K-ATPase (ouabain). RESULTS All agonists concentration-dependently relaxed PCAs. L-NAME, charybdotoxin + apamin, KCl, and ouabain shifted the bradykinin concentration-response curve (CRC) approximately 10-fold to the right. BaCl2 did not exert additional effects on top of ouabain. Full blockade of bradykinin was obtained when combining L-NAME with charybdotoxin + apamin, KCl or ouabain + BaCl2. PHMBA reduced the maximum effect of bradykinin. Iberiotoxin + apamin, alone or on top of L-NAME, did not affect bradykinin, SNAP or L-SNC. ODQ and hydroxocobalamin shifted the SNAP, L-SNC, D-SNC, and L-SNG CRCs approximately 10-fold to the right, and, in combination, fully blocked SNAP-induced effects. Charybdotoxin + apamin shifted the L-SNC and L-SNG CRCs, but not the D-SNC or SNAP CRCs, approximately 5-fold to the right. KCl and ouabain (but not BaCl2) shifted the SNAP, L-SNC and L-SNG CRCs 5-10 fold to the right. CONCLUSIONS L-S-nitrosothiols activate SKCa + IKCa channels in a stereoselective manner, whereas NO activates Na-K-ATPase. Since S-nitrosothiols decompose to NO, stored L-S-nitrosothiols may mediate bradykinin-induced, EDHF-dependent relaxation.
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Batenburg WW, Popp R, Fleming I, Vries RD, Garrelds IM, Saxena PR, Danser AHJ. Bradykinin-induced relaxation of coronary microarteries: S-nitrosothiols as EDHF? Br J Pharmacol 2004; 142:125-35. [PMID: 15066907 PMCID: PMC1574930 DOI: 10.1038/sj.bjp.0705747] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
1. To investigate whether S-nitrosothiols, in addition to NO, mediate bradykinin-induced vasorelaxation, porcine coronary microarteries (PCMAs) were mounted in myographs. 2. Following preconstriction, concentration-response curves (CRCs) were constructed to bradykinin, the NO donors S-nitroso-N-penicillamine (SNAP) and diethylamine NONOate (DEA-NONOate) and the S-nitrosothiols L-S-nitrosocysteine (L-SNC) and D-SNC. All agonists relaxed PCMAs. L-SNC was approximately 5-fold more potent than D-SNC. 3. The guanylyl cyclase inhibitor ODQ and the NO scavenger hydroxocobalamin induced a larger shift of the bradykinin CRC than the NO synthase inhibitor L-NAME, although all three inhibitors equally suppressed bradykinin-induced cGMP responses. 4. Complete blockade of bradykinin-induced relaxation was obtained with L-NAME in the presence of the large- and intermediate-conductance Ca(2+)-activated K(+)-channel (BK(Ca), IK(Ca)) blocker charybdotoxin and the small-conductance Ca(2+)-activated K(+)-channel (SK(Ca)) channel blocker apamin, but not in the presence of L-NAME, apamin and the BK(Ca) channel blocker iberiotoxin. 5. Inhibitors of cytochrome P450 epoxygenase, cyclooxygenase, voltage-dependent K(+) channels and ATP-sensitive K(+) channels did not affect bradykinin-induced relaxation. 6. SNAP-, DEA-NONOate- and D-SNC-induced relaxations were mediated entirely by the NO-guanylyl cyclase pathway. L-SNC-induced relaxations were partially blocked by charybdotoxin+apamin, but not by iberiotoxin+apamin, and this blockade was abolished following endothelium removal. ODQ, but not hydroxocobalamin, prevented L-SNC-induced increases in cGMP, and both drugs shifted the L-SNC CRC 5-10-fold to the right. 7. L-SNC hyperpolarized intact and endothelium-denuded coronary arteries. 8. Our results support the concept that bradykinin-induced relaxation is mediated via de novo synthesized NO and a non-NO, endothelium-derived hyperpolarizing factor (EDHF). S-nitrosothiols, via stereoselective activation of endothelial IK(Ca) and SK(Ca) channels, and through direct effects on smooth muscle cells, may function as an EDHF in porcine coronary microarteries.
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Affiliation(s)
| | - Rüdiger Popp
- Institut für Kardiovaskuläre Physiologie, Klinikum der J.W. Goethe-Universität, Frankfurt am Main, Germany
| | - Ingrid Fleming
- Institut für Kardiovaskuläre Physiologie, Klinikum der J.W. Goethe-Universität, Frankfurt am Main, Germany
| | - René de Vries
- Department of Pharmacology, Erasmus MC, Rotterdam, The Netherlands
| | | | - Pramod R Saxena
- Department of Pharmacology, Erasmus MC, Rotterdam, The Netherlands
| | - A H Jan Danser
- Department of Pharmacology, Erasmus MC, Rotterdam, The Netherlands
- Author for correspondence:
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Batenburg WW, Garrelds IM, van Kats JP, Saxena PR, Danser AHJ. Mediators of bradykinin-induced vasorelaxation in human coronary microarteries. Hypertension 2003; 43:488-92. [PMID: 14691197 DOI: 10.1161/01.hyp.0000110904.95771.26] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To investigate the mediators of bradykinin-induced vasorelaxation in human coronary microarteries (HCMAs), HCMAs (diameter approximately 300 microm) obtained from 42 heart valve donors (20 men and 22 women; age range, 3 to 65 years; mean age, 46 years) were mounted in Mulvany myographs. In the presence of the cyclooxygenase inhibitor indomethacin, bradykinin relaxed preconstricted HCMAs in a concentration-dependent manner. N(G)-nitro-L-arginine methyl ester and ODQ (inhibitors of nitric oxide [NO] synthase and guanylyl cyclase, respectively) and the NO scavenger hydroxocobalamin, either alone or in combination, shifted the bradykinin concentration-response curve to the right. Removal of H2O2 (with catalase), inhibition of cytochrome P450 epoxygenase (with sulfaphenazole or clotrimazole) or gap junctions (with 18alpha-glycyrrhetinic acid or carbenoxolone), and blockade of large- (BK(Ca)) and small- (SK(Ca)) conductance Ca2+-dependent K+ channels (with iberiotoxin and apamin), either alone or in addition to hydroxocobalamin, did not affect bradykinin. In contrast, complete blockade of bradykinin-induced relaxation was obtained when we combined the nonselective BK(Ca) and intermediate-conductance (IK(Ca)) Ca2+-dependent K+ channel blocker charybdotoxin and apamin with hydroxocobalamin. Charybdotoxin plus apamin alone were without effect. Inhibition of inwardly rectifying K+ channels (K(IR)) and Na+/K+-ATPase (with BaCl2 and ouabain, respectively) shifted the bradykinin concentration-response curve 10-fold to the right but did not exert an additional effect in the presence of hydroxocobalamin. In conclusion, bradykinin-induced relaxation in HCMAs depends on (1) the activation of guanylyl cyclase, K(IR), and Na(+)/K(+)-ATPase by NO and (2) IK(Ca) and SK(Ca) channels. The latter are activated by a factor other than NO. This factor is not a cytochrome P450 epoxygenase product or H2O2, nor does it depend on gap junctions or BK(Ca) channels.
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Affiliation(s)
- Wendy W Batenburg
- Department of Pharmacology, Erasmus Medical Center, Rotterdam, The Netherlands
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Balazy M, Abu-Yousef IA, Harpp DN, Park J. Identification of carbonyl sulfide and sulfur dioxide in porcine coronary artery by gas chromatography/mass spectrometry, possible relevance to EDHF. Biochem Biophys Res Commun 2003; 311:728-34. [PMID: 14623333 DOI: 10.1016/j.bbrc.2003.10.055] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Incubation of porcine coronary artery rings and cardiac muscle tissue in Krebs buffer followed by GC/MS analysis of the headspace gas revealed two gases, carbonyl sulfide (COS) and sulfur dioxide (SO(2)). The gases were identified by characteristic ions obtained by electron ionization, and by comparison of the retention time on a chromatographic column (GS GasPro) with standards of these gases. Stimulation of the arterial rings with acetylcholine and calcium ionophore A23187 increased the levels of SO(2) and COS in the vascular tissue. We also provide evidence that SO(2) could originate from disproportionation of a very unstable gas, sulfur monoxide (S=O). We suggest potential origins of these gases and discuss their relevance to endothelium-derived hyperpolarizing factor.
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Affiliation(s)
- Michael Balazy
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595-1612, USA.
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Rohra DK, Saito SY, Ohizumi Y. Strain-specific effects of acidic pH on contractile state of aortas from Wistar and Wistar Kyoto rats. Eur J Pharmacol 2003; 476:123-30. [PMID: 12969757 DOI: 10.1016/s0014-2999(03)02129-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effects of acidosis were investigated on the resting and precontracted aortas from Wistar and Wistar Kyoto (WKY) rats. Decrease in pH from 7.4 to 6.5, having no effect on the resting tension of Wistar aorta, induced a marked contraction of WKY aorta. Acidic pH markedly relaxed the contraction to 300 nM phenylephrine in Wistar aorta, whereas in WKY aorta, it produced a biphasic response, an initial relaxation followed by potentiation of the contraction. In aortas loaded with fura 2-AM, phenylephrine caused an increase in intracellular Ca2+ ([Ca2+]i) and a contraction in both Wistar and WKY rats. pH 6.5 produced a decrease in [Ca2+]i to a near-basal level and almost abolished the phenylephrine-induced contraction in Wistar rat aorta. However, in WKY aorta, a biphasic response, an initial decline and later a recovery of [Ca2+]i level, was observed. Interestingly, at similar sustained [Ca2+]i, the contractile response to phenylephrine in WKY aorta was potentiated under acidic pH conditions. Acidic pH-induced inhibition of the contraction to phenylephrine was unaffected by iberiotoxin, 4-aminopyridine, and glibenclamide (Ca2+-activated, delayed rectifier and ATP-sensitive K+ channel inhibitors, respectively), in aortas from both Wistar and WKY. Decrease in extracellular pH was associated with a rapid fall in intracellular pH (pHi) and the intracellular acidification profile was not different in both strains. All these results show that acidic pH induces strain-specific inhibitory and excitatory effects on the contractile state of aortas from Wistar and WKY rats, respectively. The sustained and transient relaxant responses to acidic pH in Wistar and WKY aortas, respectively, are due to decrease in [Ca2+]i levels, but this decrease in [Ca2+]i is independent of the activation of K+ channels.
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Affiliation(s)
- Dileep Kumar Rohra
- Department of Pharmaceutical Molecular Biology, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Aoba, Sendai 980-8578, Japan
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Merkus D, Haitsma DB, Fung TY, Assen YJ, Verdouw PD, Duncker DJ. Coronary blood flow regulation in exercising swine involves parallel rather than redundant vasodilator pathways. Am J Physiol Heart Circ Physiol 2003; 285:H424-33. [PMID: 12637354 DOI: 10.1152/ajpheart.00916.2002] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In dogs, only combined blockade of vasodilator pathways [via adenosine receptors, nitric oxide synthase (NOS) and ATP-sensitive K+ (KATP) channels] results in impairment of metabolic vasodilation, which suggests a redundancy design of coronary flow regulation. Conversely, in swine and humans, blocking KATP channels, adenosine receptors, or NOS each impairs coronary blood flow (CBF) at rest and during exercise. Consequently, we hypothesized that these vasodilators act in parallel rather than in redundancy to regulate CBF in swine. Swine exercised on a treadmill (0-5 km/h), during control and after blockade of KATP channels (with glibenclamide), adenosine receptors [with 8-phenyltheophylline (8-PT)], and/or NOS [with Nomega-nitro-l-arginine (l-NNA)]. l-NNA, 8-PT, and glibenclamide each reduced myocardial O2 delivery and coronary venous O2 tension. These effects of l-NNA, 8-PT, and glibenclamide were not modified by simultaneous blockade of the other vasodilators. Combined blockade of KATP channels and adenosine receptors with or without NOS inhibition was associated with increased H+ production and impaired myocardial function. However, despite an increase in O2 extraction to >90% during administration of l-NNA + 8-PT + glibenclamide, vasodilator reserve could still be recruited during exercise. Thus in awake swine, loss of KATP channels, adenosine, or NO is not compensated for by increased participation of the other two vasodilator mechanisms. These findings suggest a parallel rather than a redundancy design of CBF regulation in the porcine circulation.
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Affiliation(s)
- Daphne Merkus
- Division of Experimental Cardiology, Thoraxcenter, Erasmus Medical Center, 3000 DR Rotterdam, The Netherlands.
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Fülöp L, Szigeti G, Magyar J, Szentandrássy N, Ivanics T, Miklós Z, Ligeti L, Kovács A, Szénási G, Csernoch L, Nánási PP, Bányász T. Differences in electrophysiological and contractile properties of mammalian cardiac tissues bathed in bicarbonate - and HEPES-buffered solutions. ACTA PHYSIOLOGICA SCANDINAVICA 2003; 178:11-8. [PMID: 12713510 DOI: 10.1046/j.1365-201x.2003.01114.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
AIM The aim of this study was to compare the action potential configuration, contractility, intracellular Ca2+ and H+ concentrations in mammalian cardiac tissues bathed with Krebs and Tyrode solutions at 37 degrees C. RESULTS In Langendorff-perfused guinea-pig hearts, loaded with the fluorescent Ca2+-indicator Fura-2, or H+-sensitive dye carboxy-SNARF, shifts from Krebs to Tyrode solution caused intra-cellular acidification, increased diastolic pressure and [Ca2+]i, decreased systolic pressure and [Ca2+]i, leading to a reduction in the amplitude of [Ca2+]i transients and pulse pressure. Contractility was also depressed in canine ventricular trabeculae when transferred from Krebs to Tyrode solution. Shifts from Krebs to Tyrode solution increased the duration of action potentials in multicellular cardiac preparations excised from canine and rabbit hearts but not in isolated cardiomyocytes. All these changes in action potential morphology, contractility, [Ca2+]i and [H+]i were readily reversible by addition of 26 mmol L(-1) bicarbonate to Tyrode solution. Effects of dofetilide and CsCl, both blockers of the delayed rectifier K current, on action potential duration were compared in Krebs and Tyrode solutions. Dofetilide lengthened rabbit ventricular action potentials in a significantly greater extent in Tyrode than in Krebs solution. Exposure of canine Purkinje fibres to CsCl evoked early after depolarizations within 40 min in all preparations incubated with Tyrode solution, but not in those bathed with Krebs solution. CONCLUSION It is concluded that the marked differences in action potential morphology, [Ca2+]i, [H+]i and contractility observed between preparations bathed with Krebs and Tyrode solutions are more likely attributable to differences in the intracellular buffering capacities of the two media.
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Affiliation(s)
- L Fülöp
- Department of Physiology, University of Debrecen, H-4012 Debrecen, Hungary
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Bychkov R, Burnham MP, Richards GR, Edwards G, Weston AH, Félétou M, Vanhoutte PM. Characterization of a charybdotoxin-sensitive intermediate conductance Ca2+-activated K+ channel in porcine coronary endothelium: relevance to EDHF. Br J Pharmacol 2002; 137:1346-54. [PMID: 12466245 PMCID: PMC1573623 DOI: 10.1038/sj.bjp.0705057] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. This study characterizes the K(+) channel(s) underlying charybdotoxin-sensitive hyperpolarization of porcine coronary artery endothelium. 2. Two forms of current-voltage (I/V) relationship were evident in whole-cell patch-clamp recordings of freshly-isolated endothelial cells. In both cell types, iberiotoxin (100 nM) inhibited a current active only at potentials over +50 mV. In the presence of iberiotoxin, charybdotoxin (100 nM) produced a large inhibition in 38% of cells and altered the form of the I/V relationship. In the remaining cells, charybdotoxin also inhibited a current but did not alter the form. 3. Single-channel, outside-out patch recordings revealed a 17.1+/-0.4 pS conductance. Pipette solutions containing 100, 250 and 500 nM free Ca(2+) demonstrated that the open probability was increased by Ca(2+). This channel was blocked by charybdotoxin but not by iberiotoxin or apamin. 4. Hyperpolarizations of intact endothelium elicited by substance P (100 nM; 26.1+/-0.7 mV) were reduced by apamin (100 nM; 17.0+/-1.8 mV) whereas those to 1-ethyl-2-benzimidazolinone (1-EBIO, 600 microM, 21.0+/-0.3 mV) were unaffected (21.7+/-0.8 mV). Substance P, bradykinin (100 nM) and 1-EBIO evoked charybdotoxin-sensitive, iberiotoxin-insensitive whole-cell perforated-patch currents. 5 A porcine homologue of the intermediate-conductance Ca(2+)-activated K(+) channel (IK1) was identified in endothelial cells. 6. In conclusion, porcine coronary artery endothelial cells express an intermediate-conductance Ca(2+)-activated K(+) channel and the IK1 gene product. This channel is opened by activation of the EDHF pathway and likely mediates the charybdotoxin-sensitive component of the EDHF response.
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Affiliation(s)
- Rostislav Bychkov
- Département Diabète et Maladies Métaboliques, Institut de Recherches Servier, 92150 Suresnes, France
| | - Matthew P Burnham
- School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - Gillian R Richards
- School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - Gillian Edwards
- School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - Arthur H Weston
- School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - Michel Félétou
- Département Diabète et Maladies Métaboliques, Institut de Recherches Servier, 92150 Suresnes, France
- Author for correspondence:
| | - Paul M Vanhoutte
- Institut de Recherches Internationales Servier, 92410 Courbevoie, France
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Aschner JL, Smith TK, Kovacs N, Pinheiro JMB, Fuloria M. Mechanisms of bradykinin-mediated dilation in newborn piglet pulmonary conducting and resistance vessels. Am J Physiol Lung Cell Mol Physiol 2002; 283:L373-82. [PMID: 12114199 DOI: 10.1152/ajplung.00032.2002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Bradykinin (BK) is a potent dilator of the perinatal pulmonary circulation. We investigated segmental differences in BK-induced dilation in newborn pig large conducting pulmonary artery and vein rings and in pressurized pulmonary resistance arteries (PRA). In conducting pulmonary arteries and veins, BK-induced relaxation is abolished by endothelial disruption and by inhibition of nitric oxide (NO) synthase with nitro-L-arginine (L-NA). In PRA, two-thirds of the dilation response is L-NA insensitive. Charybdotoxin plus apamin and depolarization with KCl abolish the L-NA-insensitive dilations, findings that implicate the release of endothelium-derived hyperpolarizing factor (EDHF). However, endothelium-disrupted PRA retain the ability to dilate to BK but not to ACh or A-23187. In endothelium-disrupted PRA, dilation was inhibited by charybdotoxin. Thus in PRA, BK elicits dilation by multiple and duplicative signaling pathways. Release of NO and EDHF contributes to the response in endothelium-intact PRA; in endothelium-disrupted PRA, dilation occurs by direct activation of vascular smooth muscle calcium-dependent potassium channels. Redundant signaling pathways mediating pulmonary dilation to BK may be required to assure a smooth transition to extrauterine life.
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Affiliation(s)
- Judy L Aschner
- Department of Pediatrics, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1081, USA.
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Burnham MP, Bychkov R, Félétou M, Richards GR, Vanhoutte PM, Weston AH, Edwards G. Characterization of an apamin-sensitive small-conductance Ca(2+)-activated K(+) channel in porcine coronary artery endothelium: relevance to EDHF. Br J Pharmacol 2002; 135:1133-43. [PMID: 11877319 PMCID: PMC1573217 DOI: 10.1038/sj.bjp.0704551] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The apamin-sensitive small-conductance Ca(2+)-activated K(+) channel (SK(Ca)) was characterized in porcine coronary arteries. 2. In intact arteries, 100 nM substance P and 600 microM 1-ethyl-2-benzimidazolinone (1-EBIO) produced endothelial cell hyperpolarizations (27.8 +/- 0.8 mV and 24.1 +/- 1.0 mV, respectively). Charybdotoxin (100 nM) abolished the 1-EBIO response but substance P continued to induce a hyperpolarization (25.8 +/- 0.3 mV). 3. In freshly-isolated endothelial cells, outside-out patch recordings revealed a unitary K(+) conductance of 6.8 +/- 0.04 pS. The open-probability was increased by Ca(2+) and reduced by apamin (100 nM). Substance P activated an outward current under whole-cell perforated-patch conditions and a component of this current (38%) was inhibited by apamin. A second conductance of 2.7 +/- 0.03 pS inhibited by d-tubocurarine was observed infrequently. 4. Messenger RNA encoding the SK2 and SK3, but not the SK1, subunits of SK(Ca) was detected by RT - PCR in samples of endothelium. Western blotting indicated that SK3 protein was abundant in samples of endothelium compared to whole arteries. SK2 protein was present in whole artery nuclear fractions. 5. Immunofluorescent labelling confirmed that SK3 was highly expressed at the plasmalemma of endothelial cells and was not expressed in smooth muscle. SK2 was restricted to the peri-nuclear regions of both endothelial and smooth muscle cells. 6. In conclusion, the porcine coronary artery endothelium expresses an apamin-sensitive SK(Ca) containing the SK3 subunit. These channels are likely to confer all or part of the apamin-sensitive component of the endothelium-derived hyperpolarizing factor (EDHF) response.
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Affiliation(s)
- M P Burnham
- School of Biological Sciences, University of Manchester, Manchester M13 9PT, UK.
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