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Affiliation(s)
- CE Hill
- University Hospitals Coventry and Warwickshire NHS Trust, UK
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Chaston DJ, Haddock RE, Howitt L, Morton SK, Brown RD, Matthaei KI, Hill CE. Perturbation of chemical coupling by an endothelial Cx40 mutant attenuates endothelium-dependent vasodilation by KCa channels and elevates blood pressure in mice. Pflugers Arch 2015; 467:1997-2009. [PMID: 25369777 DOI: 10.1007/s00424-014-1640-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 10/16/2014] [Accepted: 10/21/2014] [Indexed: 10/24/2022]
Abstract
Mutant forms of connexin40 (Cx40) exist in the human population and predispose carriers to atrial fibrillation. Since endothelial expression of Cx40 is important for electrical and chemical communication within the arterial wall, carriers of mutant Cx40 proteins may be predisposed to peripheral arterial dysfunction and dysregulation of blood pressure. We have therefore studied mice expressing either a chemically dysfunctional mutant, Cx40T202S, or wild-type Cx40, with native Cx40, specifically in the endothelium. Blood pressure was measured by telemetry under normal conditions and during cardiovascular stress induced by locomotor activity, phenylephrine or nitric oxide blockade (N(ɷ)-nitro-L-arginine methyl ester hydroxide, L-NAME). Blood pressure of Cx40T202STg mice was significantly elevated at night when compared with wild-type or Cx40Tg mice, without change in mean heart rate, pulse pressure or locomotor activity. Analysis over 24 h showed that blood pressure of Cx40T202STg mice was significantly elevated at rest and additionally during locomotor activity. In contrast, neither plasma renin concentration nor pressor responses to phenylephrine or L-NAME were altered, the latter indicating that nitric oxide bioavailability was normal. In isolated, pressurised mesenteric arteries, hyperpolarisation and vasodilation evoked by SKA-31, the selective modulator of SKCa and IKCa channels, was significantly reduced in Cx40T202STg mice, due to attenuation of the SKCa component. Acetylcholine-induced ascending vasodilation in vivo was also significantly attenuated in cremaster muscle arterioles of Cx40T202STg mice, compared to wild-type and Cx40Tg mice. We conclude that endothelial expression of the chemically dysfunctional Cx40T202S reduces peripheral vasodilator capacity mediated by SKCa-dependent hyperpolarisation and also increases blood pressure.
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Affiliation(s)
- Daniel J Chaston
- John Curtin School of Medical Research, Australian National University, Canberra, ACT, 0200, Australia
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Hill CE. An aide-mémoirefor the Salter–Harris classification of paediatric growth plate fractures. Ann R Coll Surg Engl 2015. [DOI: 10.1308/rcsann.2015.0007.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Morton SK, Chaston DJ, Howitt L, Heisler J, Nicholson BJ, Fairweather S, Bröer S, Ashton AW, Matthaei KI, Hill CE. Loss of functional endothelial connexin40 results in exercise-induced hypertension in mice. Hypertension 2015; 65:662-9. [PMID: 25547341 DOI: 10.1161/hypertensionaha.114.04578] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
During activity, coordinated vasodilation of microcirculatory networks with upstream supply vessels increases blood flow to skeletal and cardiac muscles and reduces peripheral resistance. Endothelial dysfunction in humans attenuates activity-dependent vasodilation, resulting in exercise-induced hypertension in otherwise normotensive individuals. Underpinning activity-dependent hyperemia is an ascending vasodilation in which the endothelial gap junction protein, connexin (Cx)40, plays an essential role. Because exercise-induced hypertension is proposed as a forerunner to clinical hypertension, we hypothesized that endothelial disruption of Cx40 function in mice may create an animal model of this condition. To this end, we created mice in which a mutant Cx40T152A was expressed alongside wildtype Cx40 selectively in the endothelium. Expression of the Cx40T152A transgene in Xenopus oocytes and mouse coronary endothelial cells in vitro impaired both electric and chemical conductance and acted as a dominant-negative against wildtype Cx40, Cx43, and Cx45, but not Cx37. Endothelial expression of Cx40T152A in Cx40T152ATg mice attenuated ascending vasodilation, without effect on radial coupling through myoendothelial gap junctions. Using radiotelemetry, Cx40T152ATg mice showed an activity-dependent increase in blood pressure, which was significantly greater than in wildtype mice, but significantly less than in chronically hypertensive, Cx40knockout mice. The increase in heart rate with activity was also greater than in wildtype or Cx40knockout mice. We conclude that the endothelial Cx40T152A mutation attenuates activity-dependent vasodilation, producing a model of exercise-induced hypertension. These data highlight the importance of endothelial coupling through Cx40 in regulating blood pressure during activity.
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Affiliation(s)
- Susan K Morton
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.)
| | - Daniel J Chaston
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.)
| | - Lauren Howitt
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.)
| | - Jillian Heisler
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.)
| | - Bruce J Nicholson
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.)
| | - Stephen Fairweather
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.)
| | - Stefan Bröer
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.)
| | - Anthony W Ashton
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.)
| | - Klaus I Matthaei
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.)
| | - Caryl E Hill
- From the Eccles Institute of Neuroscience (S.K.M, D.J.C., L.H., C.E.H.) and Department of Molecular Bioscience (K.I.M.), The John Curtin School of Medical Research and Division of Biomedical Science and Biochemistry, Research School of Biology (S.F., S.B.), The Australian National University, Canberra, Australia; Department of Biochemistry, University of Texas Health Sciences Centre, San Antonio, Texas (J.H., B.J.N.); and Division of Perinatal Research, Kolling Institute of Medical Research, Royal North Shore Hospital, University of Sydney, Sydney, Australia (A.W.A.).
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Brewster MBS, Upadhyay PK, Hill CE. Finger tourniquets: a review of National Patient Safety Agency recommendations, available devices and current practice. J Hand Surg Eur Vol 2015; 40:214-5. [PMID: 23035002 DOI: 10.1177/1753193412462335] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- M B S Brewster
- Department of Hand Surgery, University Hospital of Birmingham, Edgbaston,UK and Department of Trauma and Orthopaedics, University Hospital Coventry and Warwickshire, Coventry, UK
| | - P K Upadhyay
- Department of Hand Surgery, University Hospital of Birmingham, Edgbaston,UK and Department of Trauma and Orthopaedics, University Hospital Coventry and Warwickshire, Coventry, UK
| | - C E Hill
- Department of Hand Surgery, University Hospital of Birmingham, Edgbaston,UK and Department of Trauma and Orthopaedics, University Hospital Coventry and Warwickshire, Coventry, UK
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Morton SK, Chaston DJ, Baillie BK, Hill CE, Matthaei KI. Regulation of endothelial-specific transgene expression by the LacI repressor protein in vivo. PLoS One 2014; 9:e95980. [PMID: 24755679 PMCID: PMC3995964 DOI: 10.1371/journal.pone.0095980] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 03/31/2014] [Indexed: 11/22/2022] Open
Abstract
Genetically modified mice have played an important part in elucidating gene function in vivo. However, conclusions from transgenic studies may be compromised by complications arising from the site of transgene integration into the genome and, in inducible systems, the non-innocuous nature of inducer molecules. The aim of the present study was to use the vascular system to validate a technique based on the bacterial lac operon system, in which transgene expression can be repressed and de-repressed by an innocuous lactose analogue, IPTG. We have modified an endothelium specific promoter (TIE2) with synthetic LacO sequences and made transgenic mouse lines with this modified promoter driving expression of mutant forms of connexin40 and an independently translated reporter, EGFP. We show that tissue specificity of this modified promoter is retained in the vasculature of transgenic mice in spite of the presence of LacO sequences, and that transgene expression is uniform throughout the endothelium of a range of adult systemic and cerebral arteries and arterioles. Moreover, transgene expression can be consistently down-regulated by crossing the transgenic mice with mice expressing an inhibitor protein LacI(R), and in one transgenic line, transgene expression could be de-repressed rapidly by the innocuous inducer, IPTG. We conclude that the modified bacterial lac operon system can be used successfully to validate transgenic phenotypes through a simple breeding schedule with mice homozygous for the LacI(R) protein.
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Affiliation(s)
- Susan K. Morton
- Blood Vessel Laboratory, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Stem Cell & Gene Targeting Laboratory, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Daniel J. Chaston
- Blood Vessel Laboratory, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Stem Cell & Gene Targeting Laboratory, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Brett K. Baillie
- Blood Vessel Laboratory, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Caryl E. Hill
- Blood Vessel Laboratory, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Klaus I. Matthaei
- Stem Cell & Gene Targeting Laboratory, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
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Chaston DJ, Baillie BK, Grayson TH, Courjaret RJ, Heisler JM, Lau KA, Machaca K, Nicholson BJ, Ashton A, Matthaei KI, Hill CE. Polymorphism in endothelial connexin40 enhances sensitivity to intraluminal pressure and increases arterial stiffness. Arterioscler Thromb Vasc Biol 2013; 33:962-70. [PMID: 23471232 DOI: 10.1161/atvbaha.112.300957] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
OBJECTIVE To determine whether impairment of endothelial connexin40 (Cx40), an effect that can occur in hypertension and aging, contributes to the arterial dysfunction and stiffening in these conditions. APPROACH AND RESULTS A new transgenic mouse strain, expressing a mutant Cx40, (Cx40T202S), specifically in the vascular endothelium, has been developed and characterized. This mutation produces nonfunctional hemichannels, whereas gap junctions containing the mutant are electrically, but not chemically, patent. Mesenteric resistance arteries from Cx40T202S mice showed increased sensitivity of the myogenic response to intraluminal pressure in vitro, compared with wild-type mice, whereas transgenic mice overexpressing native Cx40 (Cx40Tg) showed reduced sensitivity. In control and Cx40Tg mice, the sensitivity to pressure of myogenic constriction was modulated by both NO and endothelium-derived hyperpolarization; however, the endothelium-derived hyperpolarization component was absent in Cx40T202S arteries. Analysis of passive mechanical properties revealed that arterial stiffness was enhanced in vessels from Cx40T202S mice, but not in wild-type or Cx40Tg mice. CONCLUSIONS Introduction of a mutant form of Cx40 in the endogenous endothelial Cx40 population prevents endothelium-derived hyperpolarization activation during myogenic constriction, enhancing sensitivity to intraluminal pressure and increasing arterial stiffness. We conclude that genetic polymorphisms in endothelial Cx40 can contribute to the pathogenesis of arterial disease.
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Affiliation(s)
- Daniel J Chaston
- John Curtin School of Medical Research, The Australian National University, Bldg 131 Garran Rd, Acton Australian Capital Territory 0200 Australia.
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Howitt L, Chaston DJ, Sandow SL, Matthaei KI, Edwards FR, Hill CE. Spreading vasodilatation in the murine microcirculation: attenuation by oxidative stress-induced change in electromechanical coupling. J Physiol 2013; 591:2157-73. [PMID: 23440962 PMCID: PMC3634526 DOI: 10.1113/jphysiol.2013.250928] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 02/19/2013] [Indexed: 12/17/2022] Open
Abstract
Regulation of blood flow in microcirculatory networks depends on spread of local vasodilatation to encompass upstream arteries; a process mediated by endothelial conduction of hyperpolarization. Given that endothelial coupling is reduced in hypertension, we used hypertensive Cx40ko mice, in which endothelial coupling is attenuated, to investigate the contribution of the renin-angiotensin system and reduced endothelial cell coupling to conducted vasodilatation of cremaster arterioles in vivo. When the endothelium was disrupted by light dye treatment, conducted vasodilatation, following ionophoresis of acetylcholine, was abolished beyond the site of endothelial damage. In the absence of Cx40, sparse immunohistochemical staining was found for Cx37 in the endothelium, and endothelial, myoendothelial and smooth muscle gap junctions were identified by electron microscopy. Hyperpolarization decayed more rapidly in arterioles from Cx40ko than wild-type mice. This was accompanied by a shift in the threshold potential defining the linear relationship between voltage and diameter, increased T-type calcium channel expression and increased contribution of T-type (3 μmol l(-1) NNC 55-0396), relative to L-type (1 μmol l(-1) nifedipine), channels to vascular tone. The change in electromechanical coupling was reversed by inhibition of the renin-angiotensin system (candesartan, 1.0 mg kg(-1) day(-1) for 2 weeks) or by acute treatment with the superoxide scavenger tempol (1 mmol l(-1)). Candesartan and tempol treatments also significantly improved conducted vasodilatation. We conclude that conducted vasodilatation in Cx40ko mice requires the endothelium, and attenuation results from both a reduction in endothelial coupling and an angiotensin II-induced increase in oxidative stress. We suggest that during cardiovascular disease, the ability of microvascular networks to maintain tissue integrity may be compromised due to oxidative stress-induced changes in electromechanical coupling.
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Affiliation(s)
- Lauren Howitt
- John Curtin School of Medical Research, Australian National University, Canberra ACT 0200, Australia
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Chaston DJ, Baillie BK, Grayson TH, Courjaret RJ, Heisler JM, Lau KA, Machaca K, Nicholson BJ, Ashton A, Matthaei KI, Hill CE. Expression of dysfunctional connexin40 in vascular endothelium enhances myogenic constriction and reduces artery distensibility. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.1138.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Daniel J Chaston
- Eccles Institute for NeuroscienceAustralian National UniversityCanberraAustralia
| | - Brett K Baillie
- Eccles Institute for NeuroscienceAustralian National UniversityCanberraAustralia
| | - T Hilton Grayson
- Eccles Institute for NeuroscienceAustralian National UniversityCanberraAustralia
| | - Raphael J Courjaret
- Department of Physiology and BiophysicsWeill Cornell Medical College‐QatarDohaQatar
| | - Jillian M Heisler
- Department of BiochemistryUniversity of Texas Health Sciences CenterSan AntonioTX
| | - Katherine A Lau
- Division of Perinatal ResearchUnivesity of SydneySydneyAustralia
| | - Khaled Machaca
- Department of Physiology and BiophysicsWeill Cornell Medical College‐QatarDohaQatar
| | - Bruce J Nicholson
- Department of BiochemistryUniversity of Texas Health Sciences CenterSan AntonioTX
| | - Anthony Ashton
- Division of Perinatal ResearchUnivesity of SydneySydneyAustralia
| | - Klaus I Matthaei
- Department of Molecular BiosciencesAustralian National UniversityCanberraAustralia
| | - Caryl E Hill
- Eccles Institute for NeuroscienceAustralian National UniversityCanberraAustralia
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Haddock RE, Hill CE, Sobey CG, Drummond GR. Sympathetic hyperinnervation in obesity is associated with oxidative stress and inflammatory cell NGF synthesis. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.699.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Caryl E Hill
- Eccles Instititue of NeuroscienceAustralian National UniversityCanberraAustralia
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Howitt L, Kuo IY, Ellis A, Chaston DJ, Shin HS, Hansen PB, Hill CE. Chronic deficit in nitric oxide elicits oxidative stress and augments T-type calcium-channel contribution to vascular tone of rodent arteries and arterioles. Cardiovasc Res 2013; 98:449-57. [DOI: 10.1093/cvr/cvt043] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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Abstract
The mechanism enabling coordination of the resistance of feed arteries with microcirculatory arterioles to rapidly regulate tissue blood flow in line with changes in metabolic demand has preoccupied scientists for a quarter of a century. As experiments uncovered the underlying electrical events, it was frequently questioned how vasodilation could conduct over long distances without appreciable attenuation. This perspective reviews the data pertinent to this phenomenon and provides evidence that this remarkable response could be made possible by a simple mechanism based on the steep relationship between membrane potential and calcium entry demonstrated by the voltage-dependent calcium channels which mediate the control of vascular tone in vivo.
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Affiliation(s)
- Caryl E Hill
- Department of Neuroscience, The John Curtin School of Medical Research, The Australian National University, Acton, ACT, Australia.
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Takenaka T, Inoue T, Okada H, Ohno Y, Miyazaki T, Chaston DJ, Hill CE, Suzuki H. Altered gap junctional communication and renal haemodynamics in Zucker fatty rat model of type 2 diabetes. Diabetologia 2011; 54:2192-201. [PMID: 21573906 DOI: 10.1007/s00125-011-2175-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Accepted: 03/29/2011] [Indexed: 12/29/2022]
Abstract
AIMS/HYPOTHESIS We examined the link between altered gap junctional communication and renal haemodynamic abnormalities in diabetes in studies performed on Zucker lean (ZL) and the Zucker diabetic fatty (ZDF) rat model of type 2 diabetes. METHODS The abundance of connexin (Cx) 37, 40 and 43 was assessed by western blot and immunohistochemistry. Renal haemodynamics was characterised with GAP peptides, which are Cx mimetics, to inhibit gap junctions as a probe in both strains. RESULTS ZDF rats exhibited higher plasma glucose, 8-epi-prostaglandin F2α excretion, renal plasma flow and GFR than ZL rats. In ZDF rat kidney phosphorylation of Cx43 was enhanced compared with that in ZL rats. Immunohistochemical study revealed that the density of abundance of Cx37 in renin-secreting cells was significantly reduced in ZDF rats. Although renal autoregulation was markedly impaired in ZDF rats, it was preserved in ZL rats. GAP27 for Cx37,43 and for Cx40 impaired renal autoregulation in ZL rats, but failed to induce further alterations in renal autoregulation in ZDF rats. CONCLUSIONS/INTERPRETATION Our findings indicate that ZDF rats have glomerular hyperfiltration with impaired autoregulation. They also demonstrate enhanced phosphorylation of Cxs and reduced production of Cxs in ZDF rat kidney, especially of Cx37 in renin-secreting cells. Finally, our data suggest that an impairment of gap junctional communication in juxtaglomerular apparatus plays a role in altered renal autoregulation in diabetes.
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Affiliation(s)
- T Takenaka
- Department of Nephrology, Faculty of Medicine, Saitama Medical University, 38 Moro-hongo Moroyama, Iruma, Saitama 350-0495, Japan.
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Abstract
While a close correlation exists in obese humans between sympathetic, adrenergic hyperactivity and structural and functional organ damage, a role for the co-transmitter, ATP, in vascular function remains unexplored. We therefore studied sympathetic nerve-mediated responses of pressurised small mesenteric arteries from control and obese rats. Diet-induced obesity significantly increased the amplitude of vasoconstriction to transmural nerve stimulation (1-10 Hz; P <0.05). At 1 and 5 Hz, both adrenergic and purinergic responses were significantly augmented, while only the purinergic component was increased at 10 Hz (P <0.05). Nerve stimulation at 1 Hz evoked contractions and underlying excitatory junction potentials (EJPs), which were both significantly increased in amplitude during obesity (P <0.05) and abolished by αβ-methylene ATP (1 μM; desensitises purinergic receptors). The rise time and rate of decay of these EJPs were significant decreased (P <0.05), without change in resting membrane potential. Amplitude and frequency of spontaneous EJPs and the density of perivascular sympathetic nerves were also significantly increased (P <0.05). Inhibition of sensory neurotransmitter release (capsaicin; 10 μM) significantly increased the amplitude of nerve-mediated contraction (P <0.05), with a greater effect in control than obese animals, although the density of sensory nerves was unaffected by obesity. We demonstrate that sympathetic nerve-mediated vasoconstriction is enhanced by diet-induced obesity due to upregulation of purinergic, in addition to adrenergic, neurotransmission. Changes result from increased perivascular sympathetic innervation and release of ATP. We conclude that augmented sympathetic control of vasoconstriction induced by obesity could contribute directly to hypertension and global organ damage. A decrease in sensitivity to sensory vasodilatory neurotransmitters may also affect these processes.
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Affiliation(s)
- Rebecca E Haddock
- Department of Neuroscience, John Curtin School of Medical Research, Australian National University, GPO Box 334, Canberra, ACT, 0200, Australia.
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Matthaei KI, Frese M, Hill CE. Is the p150 isoform of the RNA editing enzyme Adenosine Deaminase 1 really responsible for embryonic lethality? Proc Natl Acad Sci U S A 2011; 108:E43; author reply E44. [PMID: 21402945 PMCID: PMC3064400 DOI: 10.1073/pnas.1100419108] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Klaus I. Matthaei
- The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, 0200, Australia; and
| | - Michael Frese
- Faculty of Applied Science, The University of Canberra, Canberra, Australian Capital Territory, 2617, Australia
| | - Caryl E. Hill
- The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, 0200, Australia; and
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Wölfle SE, Chaston DJ, Goto K, Sandow SL, Edwards FR, Hill CE. Non-linear relationship between hyperpolarisation and relaxation enables long distance propagation of vasodilatation. J Physiol 2011; 589:2607-23. [PMID: 21486765 DOI: 10.1113/jphysiol.2010.202580] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Blood flow is adjusted to tissue demand through rapidly ascending vasodilatations resulting from conduction of hyperpolarisation through vascular gap junctions. We investigated how these dilatations can spread without attenuation if mediated by an electrical signal. Cremaster muscle arterioles were studied in vivo by simultaneously measuring membrane potential and vessel diameter. Focal application of acetylcholine elicited hyperpolarisations which decayed passively with distance from the local site,while dilatation spread upstream without attenuation. Analysis of simultaneous recordings at the local site revealed that hyperpolarisation and dilatation were only linearly related over a restricted voltage range to a threshold potential, beyond which dilatation was maximal. Experimental data could be simulated in a computational model with electrotonic decay of hyperpolarisation but imposition of this threshold. The model was tested by reducing the amplitude of the local hyperpolarisation which led to entry into the linear range closer to the local site and decay of dilatation. Serial section electron microscopy and light dye treatment confirmed that the spread of dilatation occurred through the endothelium and that the two cell layers were tightly coupled. Generality of the mechanism was demonstrated by applying the model to the attenuated propagation of dilatation found in larger arteries.We conclude that long distance spread of locally initiated dilatations is not due to a regenerative electrical phenomenon, but rather a restricted linear relationship between voltage and vessel tone, which minimises the impact of electrotonic decay of voltage. Disease-related alterations in endothelial coupling or ion channel expression could therefore decrease the ability to adjust blood flow to meet metabolic demand.
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Affiliation(s)
- Stephanie E Wölfle
- John Curtin School of Medical Research, GPO Box 334, Australian National University, Canberra, ACT, 2601, Australia.
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Abstract
While L-type voltage-dependent calcium channels have long been considered the predominant source of calcium for myogenic constriction, recent studies of both cerebral and systemic circulations have provided evidence for the prominent expression of other members of the voltage-dependent calcium channel family, in particular the low voltage activated T-type channels. Although physiological studies have not supported the involvement of a classical low voltage activated, T-type channel in vascular function, evidence is accumulating that points to the involvement of a non-L-type, high voltage activated channel with sensitivity to T-type channel antagonists. We propose that this may arise due to expression of a T-type channel splice variant with unique biophysical characteristics resulting in a more depolarised profile. Expression of these channels in smooth muscle cells would broaden the voltage range over which sustained calcium influx occurs, while expression of T-type channels in endothelial cells could provide a feedback mechanism to prevent excessive vasoconstriction. Perturbation of this balance during pathophysiological conditions by upregulation of channel expression and endothelial dysfunction could contribute to vasospastic conditions and therapy-refractory hypertension.
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Affiliation(s)
- Ivana Y-T Kuo
- Department of Neuroscience, John Curtin School of Medical Research, GPO Box 334, Canberra, ACT, Australia 0200
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Wölfle SE, Navarro-Gonzalez MF, Grayson TH, Stricker C, Hill CE. Involvement of nonselective cation channels in the depolarisation initiating vasomotion. Clin Exp Pharmacol Physiol 2010; 37:536-43. [PMID: 20529092 DOI: 10.1111/j.1440-1681.2009.05350.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. Coordinated oscillations in diameter occur spontaneously in cerebral vessels and depend on the opening of voltage dependent calcium channels. However, the mechanism that induces the initial depolarisation has remained elusive. We investigated the involvement of canonical transient receptor potential (TRPC) channels, which encode nonselective cation channels passing Na(+) and Ca(2+) currents, by measuring changes in diameter, intracellular Ca(2+) and membrane potential in branches of juvenile rat basilar arteries. 2. Removal of extracellular Ca(2+) abolished vasomotion and relaxed arteries, but paradoxically produced depolarisation. 3. Decrease in temperature to 24 degrees C or inhibition of phospholipase C (PLC) abolished vasomotion, hyperpolarised and relaxed arteries and decreased intracellular Ca(2+). 4. Reduction in the driving force for Na(+) through decrease in extracellular Na(+) produced similar effects and prevented the depolarisation elicited by removal of extracellular Ca(2+). 5. Nonselective TRP channel blockers, SKF96365 and gadolinium, mimicked the effects of inhibition of the PLC pathway. 6. Depolarisation of vessels in which TRP channels were blocked with SKF96365 reinstated vascular tone and vasomotion. 7. Quantitative polymerase chain reaction revealed TRPC1 as the predominantly expressed TRPC subtype. 8. Incubation with a function blocking TRPC1 antibody delayed the onset of vasomotion. 9. We conclude that nonselective cation channels contribute to vasoconstriction and vasomotion of cerebral vessels by providing an Na(+)-induced depolarisation that activates voltage dependent calcium channels. Our antibody data suggest the involvement of TRPC1 channels that might provide a target for treatment of therapy-refractory vasospasm.
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Affiliation(s)
- Stephanie E Wölfle
- Neuroscience Program, The John Curtin School of Medical Research, Australian National University, Canberra ACT 2601, Australia.
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19
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Abstract
Although dihydropyridines are widely used for the treatment of vasospasm, their effectiveness is questionable, suggesting that other voltage-dependent calcium channels (VDCCs) contribute to control of cerebrovascular tone. This study therefore investigated the role of dihydropyridine-insensitive VDCCs in cerebrovascular function. Using quantitative PCR and immunohistochemistry, we found mRNA and protein for L-type (Ca(V)1.2) and T-type (Ca(V)3.1 and Ca(V)3.2) channels in adult rat basilar and middle cerebral arteries and their branches. Immunoelectron microscopy revealed both L- and T-type channels in smooth muscle cell (SMC) membranes. Using patch clamp electrophysiology, we found that a high-voltage-activated calcium current, showing T-type channel kinetics and insensitivity to nifedipine and nimodipine, comprised approximately 20% of current in SMCs of the main arteries and approximately 45% of current in SMCs from branches. Both components were abolished by the T-type antagonists mibefradil, NNC 55-0396, and efonidipine. Although nifedipine completely blocked vasoconstriction in pressurized basilar arteries, a nifedipine-insensitive constriction was found in branches and this increased in magnitude as vessel size decreased. We conclude that a heterogeneous population of VDCCs contributes to cerebrovascular function, with dihydropyridine-insensitive channels having a larger role in smaller vessels. Sensitivity of these currents to nonselective T-type channel antagonists suggests that these drugs may provide a more effective treatment for therapy-refractory cerebrovascular constriction.
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Affiliation(s)
- Ivana Y Kuo
- John Curtin School of Medical Research, ANU College of Medicine, Biology and Environment, The Australian National University, Canberra, Australian Capital Territory, Australia
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Wölfle SE, Navarro-Gonzalez MF, Grayson TH, Stricker C, Hill CE. Involvement of nonselective cation channels in the depolarisation initiating vasomotion. Clin Exp Pharmacol Physiol 2010. [DOI: 10.1111/j.1440-1681.2010.05350.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ellis A, Goto K, Chaston DJ, Brackenbury TD, Meaney KR, Falck JR, Wojcikiewicz RJH, Hill CE. Enalapril treatment alters the contribution of epoxyeicosatrienoic acids but not gap junctions to endothelium-derived hyperpolarizing factor activity in mesenteric arteries of spontaneously hypertensive rats. J Pharmacol Exp Ther 2009; 330:413-22. [PMID: 19411610 DOI: 10.1124/jpet.109.152116] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Reduction in endothelium-derived hyperpolarizing factor (EDHF)-mediated dilatory function in large, elastic arteries during hypertension is reversed after blood pressure normalization. We investigated whether similar mechanisms occurred in smaller mesenteric resistance arteries from aged Wistar-Kyoto (WKY) rats, spontaneously hypertensive rats (SHRs), and SHRs treated with the angiotensin-converting enzyme inhibitor, enalapril, using immunohistochemistry, serial-section electron microscopy, electrophysiology and wire myography. Unlike the superior mesenteric artery, EDHF relaxations in muscular mesenteric arteries were not reduced in SHRs, although morphological differences were found in the endothelium and smooth muscle. In WKY rats, SHRs and enalapril-treated SHRs, relaxations were mediated by small-, large-, and intermediate-conductance calcium-activated potassium channels, which were distributed in the endothelium, smooth muscle, and both layers, respectively. However, only WKY hyperpolarizations and relaxations were sensitive to gap junction blockers, and these arteries expressed more endothelial and myoendothelial gap junctions than arteries from SHRs. Responses in WKY rats, but not SHRs, were also reduced by inhibitors of epoxyeicosatrienoic acids (EETs), 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE) and miconazole, although sensitivity to EET regioisomers was endothelium-independent in all rats. Enalapril treatment of SHRs reduced blood pressure and restored sensitivity to 14,15-EEZE, but not to gap junction blockers, and failed to reverse the morphological changes. In conclusion, the mechanisms underlying EDHF in muscular mesenteric arteries differ between WKY rats and SHRs, with gap junctions and EETs involved only in WKY rats. However, reduction of blood pressure in SHRs with enalapril restored a role for EETs, but not gap junctions, without reversing morphological changes, suggesting a differential control of chemical and structural alterations.
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Affiliation(s)
- Anthie Ellis
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra ACT 0200, Australia
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Wolfle SE, Navarro‐Gonzalez MF, Beech DJ, Hill CE. TRP channels provide the depolarisation initiating vasomotion and vessel tone in cerebral resistance arteries. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.627.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - David J Beech
- Institute of Membrane and Systems BiologyUniversity of LeedsLeedsUnited Kingdom
| | - Caryl E Hill
- Division of NeuroscienceAustralian National UniversityCanberraACTAustralia
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Ellis A, Goto K, Brackenbury TD, Meaney KR, Falck JR, Wojcikiewicz RJ, Hill CE. Altered EDHF‐mediated dilation in spontaneously hypertensive rats following enalapril treatment. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.952.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Anthie Ellis
- Division of NeuroscienceAustralian National UniversityCanberraACT2100Australia
| | - Kenichi Goto
- Division of NeuroscienceAustralian National UniversityCanberraACT2100Australia
| | | | - Kate R Meaney
- Division of NeuroscienceAustralian National UniversityCanberraACT2100Australia
| | - John R Falck
- Biochemistry, Southwestern Medical CentreUniversity of Texas, Dallas, TXDallasTX
| | | | - Caryl E Hill
- Division of NeuroscienceAustralian National UniversityCanberraACT2100Australia
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Kuo IY, Chan-Ling T, Wojcikiewicz RJ, Hill CE. Limited intravascular coupling in the rodent brainstem and retina supports a role for glia in regional blood flow. J Comp Neurol 2009; 511:773-87. [PMID: 18925566 DOI: 10.1002/cne.21873] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Regional synaptic activity induces local increases in perfusion that are coupled to upstream vasodilation and improved blood flow. In the cerebral circulation, it has been proposed that astrocytes mediate the link between the initiating stimulus and local vasodilation through propagated intracellular calcium waves. In the systemic circulation the mechanism by which local vasodilation triggers upstream alterations in blood flow involves electrotonic propagation of hyperpolarization via endothelial gap junctions, although less is known concerning the cerebral circulation. The present study aimed to investigate the extent of coupling in microvessels of the rodent brainstem and retina and the subtypes of intracellular calcium stores that might mediate astrocytic signaling. Within the brainstem, connexins (Cxs) 37 and 40 were restricted to the endothelium of pial vessels and larger penetrating arterioles, whereas astrocytic Cxs30 and 43 were found closely associated with pre- and postsynaptic neurons and nearby microvessels. Within the rat retina, Cxs37 and 40 were expressed in large radiating arterioles, but were not found in smaller vessels on the retinal surface or in the deeper retinal layers. These Cxs were absent from all retinal vessels in mice. Astrocytes, expressing Cxs30 and 43 in the rat, but only Cx43 in the mouse, were found closely associated with superficial, but not deeper blood vessels. Inositol-trisphosphate receptors (IP(3)R) 1 and 2 were expressed within brainstem astrocytes, whereas IP(3)R1 and 3 were expressed within retinal astrocytes. Limited intravascular coupling and the proximity of astrocytic networks to blood vessels supports a role for glia in activity-dependent alterations in central blood flow.
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Affiliation(s)
- Ivana Y Kuo
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 0200, Australia
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Sandow SL, Haddock RE, Hill CE, Chadha PS, Kerr PM, Welsh DG, Plane F. WHAT'S WHERE AND WHY AT A VASCULAR MYOENDOTHELIAL MICRODOMAIN SIGNALLING COMPLEX. Clin Exp Pharmacol Physiol 2009; 36:67-76. [DOI: 10.1111/j.1440-1681.2008.05076.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Shcheglovitov A, Vitko I, Bidaud I, Baumgart JP, Navarro-Gonzalez MF, Grayson TH, Lory P, Hill CE, Perez-Reyes E. Alternative splicing within the I-II loop controls surface expression of T-type Ca(v)3.1 calcium channels. FEBS Lett 2008; 582:3765-70. [PMID: 18930057 DOI: 10.1016/j.febslet.2008.10.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Revised: 10/03/2008] [Accepted: 10/06/2008] [Indexed: 11/30/2022]
Abstract
Molecular diversity of T-type/Ca(v)3 Ca2+ channels is created by expression of three genes and alternative splicing of those genes. Prompted by the important role of the I-II linker in gating and surface expression of Ca(v)3 channels, we describe here the properties of a novel variant that partially deletes this loop. The variant is abundantly expressed in rat brain, even exceeding transcripts with the complete exon 8. Electrophysiological analysis of the Delta8b variant revealed enhanced current density compared to Ca(v)3.1a, but similar gating. Luminometry experiments revealed an increase in the expression of Delta8b channels at the plasma membrane. We conclude that alternative splicing of Ca(v)3 channels regulates surface expression and may underlie disease states in which T-channel current density is increased.
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Navarro-Gonzalez MF, Grayson TH, Meaney KR, Cribbs LL, Hill CE. Non-L-type voltage-dependent calcium channels control vascular tone of the rat basilar artery. Clin Exp Pharmacol Physiol 2008; 36:55-66. [PMID: 18759855 DOI: 10.1111/j.1440-1681.2008.05035.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. Constriction of cerebral arteries is considered to depend on L-type voltage-dependent calcium channels (VDCCs); however, many previous studies have used antagonists with potential non-selective actions. Our aim was to determine the expression and function of VDCCs in the rat basilar artery. 2. The relative expression of VDCC subtypes was assessed using quantitative polymerase chain reaction and immunohistochemistry. Data were correlated with physiological studies of vascular function. Domains I-II of the T channel subtypes expressed in the rat basilar artery were cloned and sequenced. 3. Blockade of L-type channels with nifedipine had no effect on vascular tone. In contrast, in the presence of nifedipine, hyperpolarization of short arterial segments produced relaxation, whereas depolarization of quiescent segments evoked constriction. 4. The mRNA and protein for L- and T-type VDCCs were strongly expressed in the main basilar artery and side branches, with Ca(V)3.1 and Ca(V)1.2 the predominant subtypes. 5. T-Type VDCC blockers (i.e. 1 micromol/L mibefradil, 10 micromol/L pimozide and 100 micromol/L flunarizine) decreased intracellular calcium in smooth muscle cells, relaxed and hyperpolarized arteries, whereas nickel chloride (100 micromol/L) had no effect. In contrast with nifedipine, 10 micromol/L nimodipine produced hyperpolarization and relaxation. 6. When arteries were relaxed with 10 micromol/L U73122 (a phospholipase C inhibitor) in the presence of nifedipine, 40 mmol/L KCl evoked depolarization and constriction, which was significantly reduced by 1 micromol/L mibefradil. 7. Sequencing of domains I-II revealed splice variants of Ca(V)3.1, which may impact on channel activity. 8. We conclude that vascular tone of the rat basilar artery results from calcium influx through nifedipine-insensitive VDCCs with pharmacology consistent with Ca(V)3.1 T-type channels.
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Affiliation(s)
- Manuel F Navarro-Gonzalez
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia
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Kingsolver JG, Hoekstra HE, Hoekstra JM, Berrigan D, Vignieri SN, Hill CE, Hoang A, Gibert P, Beerli P. The strength of phenotypic selection in natural populations. Am Nat 2008; 157:245-61. [PMID: 18707288 DOI: 10.1086/319193] [Citation(s) in RCA: 1265] [Impact Index Per Article: 79.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
How strong is phenotypic selection on quantitative traits in the wild? We reviewed the literature from 1984 through 1997 for studies that estimated the strength of linear and quadratic selection in terms of standardized selection gradients or differentials on natural variation in quantitative traits for field populations. We tabulated 63 published studies of 62 species that reported over 2,500 estimates of linear or quadratic selection. More than 80% of the estimates were for morphological traits; there is very little data for behavioral or physiological traits. Most published selection studies were unreplicated and had sample sizes below 135 individuals, resulting in low statistical power to detect selection of the magnitude typically reported for natural populations. The absolute values of linear selection gradients |beta| were exponentially distributed with an overall median of 0.16, suggesting that strong directional selection was uncommon. The values of |beta| for selection on morphological and on life-history/phenological traits were significantly different: on average, selection on morphology was stronger than selection on phenology/life history. Similarly, the values of |beta| for selection via aspects of survival, fecundity, and mating success were significantly different: on average, selection on mating success was stronger than on survival. Comparisons of estimated linear selection gradients and differentials suggest that indirect components of phenotypic selection were usually modest relative to direct components. The absolute values of quadratic selection gradients |gamma| were exponentially distributed with an overall median of only 0.10, suggesting that quadratic selection is typically quite weak. The distribution of gamma values was symmetric about 0, providing no evidence that stabilizing selection is stronger or more common than disruptive selection in nature.
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Affiliation(s)
- J G Kingsolver
- Department of Zoology, University of Washington, Seattle, Washington 98195, USA.
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Hendry IA, Hill CE, Bonyhady RE. Interactions between developing autonomic neurons and their target tissues. Ciba Found Symp 2008; 83:194-212. [PMID: 6170492 DOI: 10.1002/9780470720653.ch10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Neurons critically depend on contact with the correct target tissue in order to survive and mature. The number of neurons surviving in a nerve centre directly depends on the size of the peripheral field in innervates. It has been proposed that target tissues release a neurotrophic substance (retrophin) which is internalized by nerve terminals and retrogradely transported to the perikarya where its action results in the survival of appropriate neurons. In the sympathetic nervous system, nerve growth factor probably acts as a retrophin. Similar retrophins must exist for other neuronal systems. In order to identify a parasympathetic retrophin two approaches have been taken. One was to grow appropriate target tissues with radiolabelled amino acids and to determine whether the proteins synthesized and released by these target tissues were retrogradely transported by parasympathetic neurons in vivo. The other approach was to show that a purified neurotrophic factor for the chick ciliary ganglion could be retrogradely transported by parasympathetic neurons. The results have suggested that at least two retrophins are involved in the normal development of the autonomic nervous system: one, nerve growth factor, for the sympathetic nervous system and the other, as yet unnamed, for the parasympathetic system.
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Affiliation(s)
- Caryl E Hill
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT, 2601, Australia.
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Abstract
Gap junctions are present in the juxtaglomerular apparatus enabling intercellular communication. Our study determined the location of different connexin subtypes within the juxtaglomerular apparatus of the rat, and the role of these subtypes in renal hemodynamics through the use of specific mimetic peptides. Immunohistochemical analysis showed connexins 37 and 40 expression in the endothelial and renin-secreting cells of the afferent arteriole, while connexin 40 was also found in extra- and intraglomerular mesangial cells. In contrast, connexin 43 was weakly expressed in endothelial cells of the afferent arteriole and within the glomerulus. Intra-renal infusion of the peptides (GAP) reported to block specific gap junctions ((Cx37,43)GAP27 or (Cx40)GAP27), elevated blood pressure, plasma renin activity, and angiotensin II levels, while decreasing renal plasma flow without a significant change in the glomerular filtration rate. Subsequent restoration of blood pressure reduced both renal plasma flow and glomerular filtration rate. In contrast, (Cx43)GAP26 reduced glomerular filtration rate without alterations in blood pressure, renal plasma flow, plasma renin activity, or angiotensin II levels. Hence, connexins 37 and 40 are expressed in the rat juxtaglomerular apparatus and these proteins control, in part, the renin-angiotensin system and renal autoregulation.
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Affiliation(s)
- T Takenaka
- Department of Nephrology, Saitama Medical College, Saitama, Japan
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Takenaka T, Inoue T, Kanno Y, Okada H, Hill CE, Suzuki H. Connexins 37 and 40 transduce purinergic signals mediating renal autoregulation. Am J Physiol Regul Integr Comp Physiol 2008; 294:R1-11. [PMID: 17928514 DOI: 10.1152/ajpregu.00269.2007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Our previous data indicated that various subtypes of connexin (Cx) were expressed in the juxtaglomerular apparatus. Experiments were performed to characterize the effects on renal autoregulation of specific mimetic peptides that inhibit these Cx subtypes in Wistar-Kyoto rats. Intrarenal infusion of (Cx37,43)GAP27 increased autoregulatory index of renal plasma flow (0.06 +/- 0.05 to 0.47 +/- 0.06, n = 6, P < 0.05) and glomerular filtration rate (GFR; 0.01 +/- 0.07 to 0.49 +/- 0.07, P < 0.05). The additional administration of 8-cyclopentyl- 1,3-dipropylxanthine (CPX) produced a further elevation of autoregulatory index of RPF (0.86 +/- 0.07, P < 0.05) and GFR (0.88 +/- 0.09, P < 0.05), compared with (Cx37,43)GAP27 alone. However, the addition of pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid (PPADS) to (Cx37,43)GAP27 did not. Combined treatment with CPX and PPADS markedly worsened autoregulatory index of RPF (0.04 +/- 0.10 to 0.81 +/- 0.06, n = 6 P < 0.01) and GFR (0.05 +/- 0.08 to 0.79 +/- 0.05, P < 0.01). (Cx40)GAP27 induced similar changes to (Cx37,43)GAP27. Renal autoregulation was preserved in the presence of (Cx43)GAP26. Our results indicate that the inhibition of gap junction impaired renal autoregulation. Furthermore, the present data provide evidence that both adenosine and purinergic receptors contribute to glomerular autoregulation. Finally, our findings suggest that gap junctions, at least in part, transduce purinergic signals mediating renal autoregulation.
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Affiliation(s)
- Tsuneo Takenaka
- Department of Nephrology, Saitama Medical College, Iruma Saitama, Japan
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Grayson TH, Ohms SJ, Brackenbury TD, Meaney KR, Peng K, Pittelkow YE, Wilson SR, Sandow SL, Hill CE. Vascular microarray profiling in two models of hypertension identifies caveolin-1, Rgs2 and Rgs5 as antihypertensive targets. BMC Genomics 2007; 8:404. [PMID: 17986358 PMCID: PMC2219888 DOI: 10.1186/1471-2164-8-404] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Accepted: 11/07/2007] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Hypertension is a complex disease with many contributory genetic and environmental factors. We aimed to identify common targets for therapy by gene expression profiling of a resistance artery taken from animals representing two different models of hypertension. We studied gene expression and morphology of a saphenous artery branch in normotensive WKY rats, spontaneously hypertensive rats (SHR) and adrenocorticotropic hormone (ACTH)-induced hypertensive rats. RESULTS Differential remodeling of arteries occurred in SHR and ACTH-treated rats, involving changes in both smooth muscle and endothelium. Increased expression of smooth muscle cell growth promoters and decreased expression of growth suppressors confirmed smooth muscle cell proliferation in SHR but not in ACTH. Differential gene expression between arteries from the two hypertensive models extended to the renin-angiotensin system, MAP kinase pathways, mitochondrial activity, lipid metabolism, extracellular matrix and calcium handling. In contrast, arteries from both hypertensive models exhibited significant increases in caveolin-1 expression and decreases in the regulators of G-protein signalling, Rgs2 and Rgs5. Increased protein expression of caveolin-1 and increased incidence of caveolae was found in both smooth muscle and endothelial cells of arteries from both hypertensive models. CONCLUSION We conclude that the majority of differences in gene expression found in the saphenous artery taken from rats with two different forms of hypertension reflect distinctive morphological and physiological alterations. However, changes in common to caveolin-1 expression and G protein signalling, through attenuation of Rgs2 and Rgs5, may contribute to hypertension through augmentation of vasoconstrictor pathways and provide potential targets for common drug development.
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Affiliation(s)
- T Hilton Grayson
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia.
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Zhang J, Kawashima S, Yokoyama M, Huang P, Hill CE. Protective effect of endothelial nitric oxide synthase against induction of chemically-induced diabetes in mice. Nitric Oxide 2007; 17:69-74. [PMID: 17658282 DOI: 10.1016/j.niox.2007.06.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 06/08/2007] [Accepted: 06/12/2007] [Indexed: 11/23/2022]
Abstract
Since activation of endothelial nitric oxide synthase has been shown to exert protective effects against the metabolic syndrome, while endothelial nitric oxide synthase knockout mice develop hyperinsulinemia and glucose intolerance, we hypothesised that endothelial nitric oxide might play a protective role against induction of diabetes. The role of endothelial nitric oxide in the development of chemically-induced diabetes has been determined using mice in which the bioavailability of endothelial nitric oxide was either increased, through upregulation of endothelial nitric oxide synthase, or absent, through deletion of endothelial nitric oxide synthase gene. Diabetes was induced intraperitoneally with either a single dose of alloxan, streptozotocin, or multiple low doses of streptozotocin and blood glucose monitored twice a week. The role of cyclic guanosine monophosphate was investigated in wildtype mice by treatment with the phosphodiesterase inhibitor, tadalafil, during diabetes induction. Results showed that the incidence of diabetes was markedly decreased in mice overexpressing endothelial nitric oxide synthase, compared to wildtype or endothelial nitric oxide synthase knockout mice, regardless of the method of diabetes induction. Under normal physiological conditions, or during diabetes induction with alloxan or multiple low doses of streptozotocin, blood glucose was significantly lower in mice overexpressing endothelial nitric oxide synthase compared to wildtype or knockout mice. Treatment with tadalafil had no effect on the incidence or severity of diabetes in wildtype mice. We conclude that upregulation of endothelial nitric oxide synthase exerts a protective action against diabetes induction through a direct effect of nitric oxide, independently of cyclic guanosine monophosphate.
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Affiliation(s)
- J Zhang
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2602, Australia
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35
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Abstract
The effects of pharmacological interventions that modulate Ca(2+) homeodynamics and membrane potential in rat isolated cerebral vessels during vasomotion (i.e., rhythmic fluctuations in arterial diameter) were simulated by a third-order system of nonlinear differential equations. Independent control variables employed in the model were [Ca(2+)] in the cytosol, [Ca(2+)] in intracellular stores, and smooth muscle membrane potential. Interactions between ryanodine- and inositol 1,4,5-trisphosphate-sensitive intracellular Ca(2+) stores and transmembrane ion fluxes via K(+) channels, Cl(-) channels, and voltage-operated Ca(2+) channels were studied by comparing simulations of oscillatory behavior with experimental measurements of membrane potential, intracellular free [Ca(2+)] and vessel diameter during a range of pharmacological interventions. The main conclusion of the study is that a general model of vasomotion that predicts experimental data can be constructed by a low-order system that incorporates nonlinear interactions between dynamical control variables.
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Affiliation(s)
- D Parthimos
- Wales Heart Research Institute, Department of Diagnostic Radiology, Cardiff University, Cardiff, UK
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36
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Goto K, Edwards FR, Hill CE. Depolarization evoked by acetylcholine in mesenteric arteries of hypertensive rats attenuates endothelium-dependent hyperpolarizing factor. J Hypertens 2007; 25:345-59. [PMID: 17211241 DOI: 10.1097/hjh.0b013e328010d616] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE During blockade of endothelium-dependent hyperpolarizing factor (EDHF), acetylcholine evoked larger and faster depolarization in mesenteric arteries of spontaneously hypertensive rats (SHR) than normotensive Wistar-Kyoto (WKY) rats. We studied the mechanism underlying this response and its role in the attenuation of EDHF. METHODS Electrophysiology, computational modelling and myography were used to study changes in membrane potential and effects on contractility. RESULTS The large acetylcholine-evoked depolarization in SHR was accompanied by contraction, but this was not seen in WKY rats. The depolarization depended on release of intracellular Ca2+ but was unaffected by nonselective cation channel inhibitors, gadolinium, lanthanum or amiloride. The depolarization was significantly reduced by the Ca2+-dependent Cl- channel inhibitors, niflumic acid or flufenamic acid, or alterations in Cl- gradients using bumetanide (Na/K/Cl transporter inhibitor) or external Cl- replacement with isethionate. These drugs altered the time course of EDHF-evoked hyperpolarizations in SHR, making them indistinguishable from those in WKY rats. EDHF-induced relaxation was less sensitive to acetylcholine in SHR than in WKY rats, but this difference was eliminated following artery pretreatment with bumetanide. Computational modelling in which the SHR fast depolarizing response was selectively modulated mimicked physiologically acquired results obtained in SHR and WKY rats during Cl- -channel blockade. CONCLUSIONS Acetylcholine evokes a fast depolarization in SHR but not in WKY rats, mediated by the opening of Ca2+-dependent Cl- channels. The depolarization is responsible for a constriction that reduces EDHF-mediated relaxation. Data suggest that Ca2+-dependent Cl- channels may provide a novel therapeutic target for improvement of endothelial dysfunction during hypertension.
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Affiliation(s)
- Kenichi Goto
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia
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37
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Gilvin PJ, Luo LZ, Baker ST, Hill CE, Rotunda JE. Type testing of an extremity finger stall dosemeter based on Harshaw TLD EXTRAD technology. Radiat Prot Dosimetry 2007; 123:329-36. [PMID: 17132668 DOI: 10.1093/rpd/ncl382] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
A new type of extremity dosemeter, which incorporates the Harshaw TLD EXTRAD dosemeter element into a PVC finger stall, has been developed. The dosemeter uses high-sensitivity lithium fluoride, (7)LiF:Mg,Cu,P (TLD-700H) in a thin 7 mg cm(-2) layer, with alternative coverings of PVC at 10 mg cm(-2) and aluminised polyester at 3.2 mg cm(-2). Results are presented of the type testing of both versions of the finger stall dosemeter against published standards.
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Affiliation(s)
- P J Gilvin
- Health Protection Agency, Radiation Protection Division, Chilton, Didcot, Oxon, UK.
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38
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Haddock RE, Meaney KR, Sandow SL, Hill CE. Non‐specific gap junction action of connexin‐mimetic peptides in the rat basilar artery. FASEB J 2007. [DOI: 10.1096/fasebj.21.6.a911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Rebecca Ellen Haddock
- PhysiologyUniversity of New South WalesSchool of Medical ScienceFaculty of MedicineWallace Worth Building, UNSW, Kensington, NSW2052Australia
- NeuroscienceJohn Curtin School of Medical ResearchAustralian National UniversityCanberra, ACT0200Australia
| | - Kate R Meaney
- NeuroscienceJohn Curtin School of Medical ResearchAustralian National UniversityCanberra, ACT0200Australia
| | - Shaun L Sandow
- PhysiologyUniversity of New South WalesSchool of Medical ScienceFaculty of MedicineWallace Worth Building, UNSW, Kensington, NSW2052Australia
| | - Caryl E Hill
- NeuroscienceJohn Curtin School of Medical ResearchAustralian National UniversityCanberra, ACT0200Australia
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39
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Haddock RE, Grayson TH, Brackenbury TD, Meaney KR, Neylon CB, Sandow SL, Hill CE. Endothelial coordination of cerebral vasomotion via myoendothelial gap junctions containing connexins 37 and 40. Am J Physiol Heart Circ Physiol 2006; 291:H2047-56. [PMID: 16815985 DOI: 10.1152/ajpheart.00484.2006] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Control of cerebral vasculature differs from that of systemic vessels outside the blood-brain barrier. The hypothesis that the endothelium modulates vasomotion via direct myoendothelial coupling was investigated in a small vessel of the cerebral circulation. In the primary branch of the rat basilar artery, membrane potential, diameter, and calcium dynamics associated with vasomotion were examined using selective inhibitors of endothelial function in intact and endothelium-denuded arteries. Vessel anatomy, protein, and mRNA expression were studied using conventional electron microscopy high-resolution ultrastructural and confocal immunohistochemistry and quantitative PCR. Membrane potential oscillations were present in both endothelial cells and smooth muscle cells (SMCs), and these preceded rhythmical contractions during which adjacent SMC intracellular calcium concentration ([Ca(2+)](i)) waves were synchronized. Endothelium removal abolished vasomotion and desynchronized adjacent smooth muscle cell [Ca(2+)](i) waves. N(G)-nitro-l-arginine methyl ester (10 microM) did not mimic this effect, and dibutyryl cGMP (300 muM) failed to resynchronize [Ca(2+)](i) waves in endothelium-denuded arteries. Combined charybdotoxin and apamin abolished vasomotion and depolarized and constricted vessels, even in absence of endothelium. Separately, (37,43)Gap27 and (40)Gap27 abolished vasomotion. Extensive myoendothelial gap junctions (3 per endothelial cell) composed of connexins 37 and 40 connected the endothelial cell and SMC layers. Synchronized vasomotion in rat basilar artery is endothelium dependent, with [Ca(2+)](i) waves generated within SMCs being coordinated by electrical coupling via myoendothelial gap junctions.
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Affiliation(s)
- Rebecca E Haddock
- Div. of Neuroscience, John Curtin School of Medical Research, Australian National Univ., Canberra, 2601 ACT Australia
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40
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Navarro‐Gonzalez MF, Hill CE. Control of tone in cerebral arteries by nifedipine‐insensitive voltage activated calcium channels. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a731-d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Caryl E. Hill
- Division of NeuroscienceJohn Curtin School of Medical ResearchAustralian National UniversityCanberra2601Australia
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41
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Hill CE, Goto K. Acetylcholine‐evoked depolarization reduces EDHF in rat mesenteric arteries during hypertension. FASEB J 2006. [DOI: 10.1096/fasebj.20.5.a1182-b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Caryl E. Hill
- NeuroscienceJohn Curtin School of Medical ResearchBuilding 54, Mills RoadActon2601Australia
| | - Kenichi Goto
- NeuroscienceJohn Curtin School of Medical ResearchBuilding 54, Mills RoadActon2601Australia
- Department of Medicine and Clinical ScienceKyushu UniversityMaidashi 3‐1‐1, Higashi‐kuFukuoka812‐8582Japan
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42
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Zhang JH, Kawashima S, Yokoyama M, Huang P, Hill CE. Increased eNOS accounts for changes in connexin expression in renal arterioles during diabetes. ACTA ACUST UNITED AC 2006; 288:1000-8. [PMID: 16892422 DOI: 10.1002/ar.a.20369] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Previous studies have shown that connexin (Cx) expression is considerably higher in the preglomerular compared to postglomerular vasculature and that these differences are accentuated during diabetes. Since nitric oxide (NO) has been reported to alter Cx expression in endothelial cells and muscle cells and NO bioavailability is altered in diabetes, we hypothesized that NO may be responsible for the changes during diabetes. Cx expression was studied using immunohistochemistry in mice in which eNOS expression was either upregulated (eNOS transgenic) or downregulated (eNOS knockout). Diabetes was induced intraperitoneally with a single dose of alloxan or multiple low doses of streptozotocin. Expression of Cx40 in smooth muscle cells of afferent arterioles was increased, while expression of Cx43 in endothelial cells of efferent arterioles was absent in eNOS transgenic mice, similar to the changes occurring in wild-type mice during diabetes. Expression of Cx40 and Cx43 in eNOS knockout mice was not different from control; however, induction of diabetes in eNOS knockout mice failed to produce any changes in Cx40 or Cx43 in either afferent or efferent arterioles. Immunohistochemistry showed that eNOS expression was increased in the endothelium of renal arterioles in wild-type diabetic and eNOS transgenic mice, but absent from arterioles of eNOS knockout mice. We conclude that changes occurring in Cx expression in afferent and efferent arterioles during diabetes may result from increased eNOS.
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Affiliation(s)
- Jian Hong Zhang
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2602, Australia
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43
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Abstract
BACKGROUND Gap junctions may play an important role in regulating renal blood flow and glomerular responses. We have therefore made a comprehensive analysis of connexin expression in the renal vasculature of control and diabetic mice since elevated glucose has been reported to down-regulate connexin 43 in vascular cells in vitro. METHODS Connexin distribution was determined with immunohistochemistry using subtype-specific and cell type-specific antibodies. Diabetes was induced with streptozotocin (120/80 mg/kg, intraperitoneally) in C57BL/6 mice. RESULTS Connexins 37, 40, and 43 were expressed in endothelial cells of the renal, lobar, arcuate, and interlobular arteries and afferent arterioles, although connexin 43 was weak in the renal and arcuate arteries. Connexin 37 was detected in the media of arcuate, interlobular arteries and afferent arterioles and connexins 37 and 40 were found in renin-secreting cells. Both connexins 37 and 40 were expressed in extraglomerular mesangial cells, connexin 40 was abundantly expressed in intraglomerular mesangial cells, but connexin 37 was limited to mesangial cells at the vascular pole. In contrast, only connexin 43 was detected in endothelial cells of efferent arterioles and there was no connexin staining in the media. In diabetes, connexin 40 was expressed in smooth muscle cells along afferent arterioles, glomerular connexin staining was more extensive and connexin 43 was detected in renin-secreting cells. In contrast connexin 43 expression in endothelial cells of efferent arterioles was markedly reduced. CONCLUSION The renal vasculature and mesangial cells are well coupled on the preglomerular side but there is little evidence that the coupling extends into the efferent arteriole. This pattern of cell coupling is accentuated during diabetes.
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Affiliation(s)
- Jianhong Zhang
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia
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44
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Abstract
Many arteries and arterioles exhibit rhythmical contractions which are synchronous over considerable distances. This vasomotion is likely to assist in tissue perfusion especially during periods of altered metabolism or perfusion pressure. While the mechanism underlying vascular rhythmicity has been investigated for many years, it has only been recently, with the advent of imaging techniques for visualizing intracellular calcium release, that significant advances have been made. These methods, when combined with mechanical and electrophysiological recordings, have demonstrated that the rhythm depends critically on calcium released from intracellular stores within the smooth muscle cells and on cell coupling via gap junctions to synchronize oscillations in calcium release amongst adjacent cells. While these factors are common to all vessels studied to date, the contribution of voltage-dependent channels and the endothelium varies amongst different vessels. The basic mechanism for rhythmical activity in arteries thus differs from its counterpart in non-vascular smooth muscle, where specific networks of pacemaker cells generate electrical potentials which drive activity within the otherwise quiescent muscle cells.
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Affiliation(s)
- Rebecca E Haddock
- Division of Neuroscience, John Curtin School of Medical Research, GPO Box 334, Canberra, ACT, 2601, Australia.
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45
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Abstract
Four connexin (Cx) molecules, namely Cx37, Cx40, Cx43 and Cx45, are expressed in the gap junctions that exist within and between the cellular layers of arteries. Endothelial cells are well coupled by large gap junctions expressing Cx37, Cx40 and, to a lesser extent, Cx43, whose expression may be more subject to regulation by physical factors. Smooth muscle cells are more heterogeneously coupled by gap junctions that are small and rare. The identity of the Cx expressed in the media may vary among different arteries. Myoendothelial gap junctions are small and more common in resistance arteries with fewer layers of smooth muscle cells. Given the small size of these gap junctions and the rapid turnover rate of Cxs, homocellular coupling in the media and heterocellular coupling between the cell layers may be subject to more dynamic control than coupling in the endothelium. Vascular gap junctions have been implicated in a number of vasomotor responses that may regulate vascular tone and blood pressure. These include the mechanism of action of the vasodilator, endothelium-derived hyperpolarizing factor (EDHF), the myogenic constriction to intramural pressure increase, the spontaneous or agonist-induced vasomotion of arteries and arterioles and the spreading vasodilation and constriction observed in microcirculatory networks. Few data are available on Cx expression in the media of resistance arteries during hypertension. Changes in the expression of Cx43 described in the media of the aorta of hypertensive rats vary with the hypertensive model studied and are likely to represent adaptations to structural changes in the vascular wall. In contrast, in the endothelium of the caudal and mesenteric arteries of spontaneously hypertensive rats, expression of Cxs is significantly decreased compared with arteries from normotensive rats and this decrease is reversed by inhibitors of the renin-angiotensin system. During hypertension, the activity of EDHF is decreased in the mesenteric artery, but this occurs much later than the initial increase in blood pressure and the decrease in endothelial Cxs, suggesting that changes in EDHF may not be causally related to hypertension or to the changes in endothelial Cxs. Upregulation of the myogenic response and the incidence of vasomotion has been reported in hypertension. Little is currently known of the effects of hypertension on spreading vasomotor responses. Deletion of specific Cxs in genetically modified mice is complicated by neonatal lethality or coordinate regulation and compensatory changes in the remaining Cxs. Nevertheless, mice in which Cx40 has been deleted are hypertensive and spreading vasodilatory responses are significantly impaired. Determination of a role for specific Cxs in the control of blood pressure must await the development of animals in which Cx expression can be modulated in a more complex temporal and tissue-specific manner.
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Affiliation(s)
- Nicole M Rummery
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia
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46
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Lan WZ, Abbas H, Lemay AM, Briggs MM, Hill CE. Electrophysiological and molecular identification of hepatocellular volume-activated K+ channels. Biochimica et Biophysica Acta (BBA) - Biomembranes 2005; 1668:223-33. [PMID: 15737333 DOI: 10.1016/j.bbamem.2004.12.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Revised: 11/26/2004] [Accepted: 12/17/2004] [Indexed: 11/30/2022]
Abstract
Although K+ channels are essential for hepatocellular function, it is not known which channels are involved in the regulatory volume decrease (RVD) in these cells. We have used a combination of electrophysiological and molecular approaches to describe the potential candidates for these channels. The dialysis of short-term cultured rat hepatocytes with a hypotonic solution containing high K+ and low Cl- concentration caused the slow activation of an outward, time-independent current under whole-cell configuration of the patch electrode voltage clamp. The reversal potential of this current suggested that K+ was the primary charge carrier. The swelling-induced K+ current (IKvol) occurred in the absence of Ca2+ and was inhibited with 1 microM Ca2+ in the pipette solution. The activation of IKvol required both Mg2+ and ATP and an increasing concentration of Mg-ATP from 0.25 through 0.5 to 0.9 mM activated IKvol increasingly faster and to a larger extent. The KCNQ1 inhibitor chromanol 293B reversibly depressed IKvol with an IC50 of 26 microM. RT-PCR detected the expression of members of the KCNQ family from KCNQ1 to KCNQ5 and of the accessory proteins KCNE1 to KCNE3 in the rat hepatocytes, but not KCNQ2 and KCNE2 in human liver. Western blotting showed KCNE3 expression in a plasma membrane-enriched fraction from rat hepatocytes. The results suggest that KCNQ1, probably with KCNE2 or KCNE3 as its accessory unit, provides a significant fraction of IKvol in rat hepatocytes.
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Affiliation(s)
- W-Z Lan
- GI Diseases Research Unit, Hotel Dieu Hospital and Queen's University, Kingston, Ontario, Canada K7L 5G2
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47
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Abstract
OBJECTIVE AND DESIGN Remodelling in the media and decreases in connexin (Cx) expression and size of endothelial cells occur in the caudal artery of spontaneously hypertensive rats (SHR). The objective of this study was to determine whether similar changes are found in the aorta and whether effects in both aorta and caudal artery are present in the pre-hypertensive period or can be reversed by antihypertensive treatment. METHODS AND RESULTS In the aorta of SHR, there was no difference in endothelial cell size although Cxs 37 and 40 were decreased, compared with normotensive Wistar-Kyoto rats. Cxs 37 and 43 were also reduced in the media. These differences were not apparent in pre-hypertensive SHR. Inhibition of angiotensin-converting enzyme (ACE) in SHR decreased blood pressure and restored Cx expression in the endothelium of both aorta and caudal artery. The decreased endothelial cell size in the caudal artery or the reduced Cxs in the media of the aorta of SHR were unaffected by ACE inhibition. CONCLUSION We conclude that cellular coupling is reduced in the endothelium of arteries of SHR, but this can be restored by inhibition of the renin-angiotensin system. Decreased cellular coupling in the media or decreased endothelial size in SHR were not reversed by this antihypertensive treatment.
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Affiliation(s)
- Nicole M Rummery
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT, 2601, Australia.
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48
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Grayson TH, Haddock RE, Murray TP, Wojcikiewicz RJH, Hill CE. Inositol 1,4,5-trisphosphate receptor subtypes are differentially distributed between smooth muscle and endothelial layers of rat arteries. Cell Calcium 2004; 36:447-58. [PMID: 15488594 DOI: 10.1016/j.ceca.2004.04.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Revised: 03/29/2004] [Accepted: 04/20/2004] [Indexed: 11/22/2022]
Abstract
In blood vessels, the ability to control vascular tone depends on extracellular calcium entry and the release of calcium from inositol 1,4,5-trisphosphate receptor (IP3R)-gated stores located in both the endothelial and smooth muscle cells of the vascular wall. Therefore, we examined mRNA expression and protein distribution of IP3R subtypes in intact aorta, basilar and mesenteric arteries of the rat. IP3R1 mRNA was predominantly expressed in all three arteries. Immunohistochemistry showed that IP3R1 was present in both the muscle and endothelial cell layers, while IP3R2 and IP3R3 were largely restricted to the endothelium. Weak expression of IP3R2 was observed in the smooth muscle of the basilar artery. Co-localisation studies of IP3R subtypes with known cellular elements showed no association of any of the three subtypes with the endothelial cell plasma membrane, but a close association between the subtypes and actin filaments was observed in all cell layers. IP3R2 was found to be present near the endothelial cell nucleus. We are the first to demonstrate differential IP3R subtype distribution between the cell layers of the intact vascular wall and hypothesise that this may underlie the diversity of IP3R-dependent responses, such as vasoconstriction, vasodilation and vasomotion, displayed by arteries.
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MESH Headings
- Animals
- Arteries/chemistry
- Arteries/metabolism
- Calcium Channels/analysis
- Calcium Channels/biosynthesis
- Endothelium, Vascular/chemistry
- Endothelium, Vascular/metabolism
- Inositol 1,4,5-Trisphosphate Receptors
- Muscle, Smooth, Vascular/chemistry
- Muscle, Smooth, Vascular/metabolism
- Protein Subunits/analysis
- Protein Subunits/biosynthesis
- Rats
- Rats, Wistar
- Receptors, Cytoplasmic and Nuclear/analysis
- Receptors, Cytoplasmic and Nuclear/biosynthesis
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Affiliation(s)
- T Hilton Grayson
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT 0200, Australia.
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49
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Goto K, Rummery NM, Grayson TH, Hill CE. Attenuation of conducted vasodilatation in rat mesenteric arteries during hypertension: role of inwardly rectifying potassium channels. J Physiol 2004; 561:215-31. [PMID: 15550469 PMCID: PMC1665331 DOI: 10.1113/jphysiol.2004.070458] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The present study was designed to elucidate whether the conduction of vasomotor responses mediated by endothelium-derived hyperpolarizing factor (EDHF) in rat mesenteric arteries is altered during hypertension. Iontophoresed acetylcholine (ACh; 500 ms) caused EDHF-mediated hyperpolarization and vasodilatation at the local site and these responses spread through the endothelium to remote sites in 12-week-old Wistar-Kyoto rats (WKY). Conducted responses were significantly attenuated in age-matched spontaneously hypertensive rats (SHR) although the rate of decay with distance did not change. Inhibition of inwardly rectifying potassium (Kir) channels (30 microM barium) eliminated the difference between WKY and SHR by attenuating conducted responses in WKY but not SHR. At the local site, barium (30 microM) significantly reduced the duration but not the amplitude of ACh-induced hyperpolarization in WKY only. Barium had no effect when the iontophoretic stimulus was reduced to 350 ms. After blockade of EDHF in SHR, ACh elicited a depolarization which our indirect data suggest spreads along the vessel in the endothelium. Messenger RNA expression of Kir2.0 genes did not differ between the strains nor did the amplitude of K(+)-induced hyperpolarization, which was abolished by disruption of the endothelium. Immunohistochemistry revealed a decrease in connexin (Cx)37 but not Cx40 or Cx43 protein in endothelial cells of SHR compared to WKY. Results suggest that conduction of EDHF-mediated responses in WKY, but not in SHR, is facilitated by activation of Kir channels at the site of ACh application and not by differences in endothelial connexin expression. Lack of Kir channel involvement in hypertension may result from reduction in the duration of the hyperpolarization due to the development of ACh-mediated depolarization, rather than to any difference in Kir subunit expression or function.
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Affiliation(s)
- Kenichi Goto
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT, 0200, Australia.
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50
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Sandow SL, Goto K, Rummery NM, Hill CE. Developmental changes in myoendothelial gap junction mediated vasodilator activity in the rat saphenous artery. J Physiol 2004; 556:875-86. [PMID: 14766938 PMCID: PMC1665009 DOI: 10.1113/jphysiol.2003.058669] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
A role for myoendothelial gap junctions (MEGJs) has been proposed in the action of the vasodilator endothelium-derived hyperpolarizing factor (EDHF). EDHF activity varies in disease and during ageing, but little is known of the role of EDHF during development when, in many organ systems, gap junctions are up-regulated. The aims of the present study were therefore to determine whether an up-regulation of heterocellular gap junctional coupling occurs during arterial development and whether this change is reflected functionally through an increased action of EDHF. Results demonstrated that in the saphenous artery of juvenile WKY rats, MEGJs were abundant and application of acetylcholine (ACh) evoked EDHF-mediated hyperpolarization and relaxation in the presence of N(omega)-nitro-l-arginine methyl ester (L-NAME) and indomethacin to inhibit nitric oxide and prostaglandins, respectively. Responses were blocked by a combination of charybdotoxin plus apamin, or 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34) plus apamin, or by blockade of gap junctions with the connexin (Cx)-mimetic peptides, (43)Gap26, (40)Gap27 and (37,43)Gap27. On the other hand, we found no evidence for the involvement of the putative chemical mediators of EDHF, eicosanoids, L-NAME-insensitive nitric oxide, hydrogen peroxide or potassium ions, since 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE), hydroxocobalamin, catalase or barium and ouabain were without effect. In contrast, in the adult saphenous artery, MEGJs were rare, EDHF-mediated relaxation was absent and hyperpolarizations were small and unstable. The present study demonstrates that MEGJs and EDHF are up-regulated during arterial development. Furthermore, the data show for the first time that this developmentally regulated EDHF is dependent on direct electrotonic coupling via MEGJs.
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MESH Headings
- 8,11,14-Eicosatrienoic Acid/analogs & derivatives
- 8,11,14-Eicosatrienoic Acid/pharmacology
- Acetylcholine/pharmacology
- Animals
- Apamin/pharmacology
- Arteries/drug effects
- Arteries/physiology
- Barium/pharmacology
- Biological Factors/physiology
- Catalase/pharmacology
- Charybdotoxin/pharmacology
- Connexin 26
- Connexins/chemistry
- Connexins/pharmacology
- Endothelium, Vascular/cytology
- Endothelium, Vascular/physiology
- Femoral Artery/drug effects
- Femoral Artery/physiology
- Gap Junctions/physiology
- Gap Junctions/ultrastructure
- Hydroxocobalamin/pharmacology
- Immunohistochemistry
- In Vitro Techniques
- Indomethacin/pharmacology
- Male
- Membrane Potentials/drug effects
- Microscopy, Electron
- Models, Biological
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/physiology
- NG-Nitroarginine Methyl Ester/pharmacology
- Oligopeptides
- Ouabain/pharmacology
- Patch-Clamp Techniques
- Peptide Fragments/pharmacology
- Phenylephrine/pharmacology
- Pyrazoles/pharmacology
- Rats
- Rats, Inbred WKY
- Vasodilation/drug effects
- Vasodilation/physiology
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Affiliation(s)
- Shaun L Sandow
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia.
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