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El-Mas MM, El-Gowelli HM, Ghazal ARM, Harraz OF, Mohy El-Din MM. Facilitation of central imidazoline I(1)-site/extracellular signal-regulated kinase/p38 mitogen-activated protein kinase signalling mediates the hypotensive effect of ethanol in rats with acute renal failure. Br J Pharmacol 2009; 158:1629-40. [PMID: 19845670 DOI: 10.1111/j.1476-5381.2009.00444.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND AND PURPOSE This study investigated the role of central sympathetic activity and related mitogen-activated protein kinase (MAPK) signalling in the cardiovascular effects of ethanol in a model of acute renal failure (ARF). EXPERIMENTAL APPROACH The effects of pharmacological interventions that inhibit peripheral or central sympathetic activity or MAPK on the cardiovascular actions of ethanol in rats with ARF induced by glycerol were evaluated. KEY RESULTS Glycerol (50%, 10 mL.kg(-1), i.m.) caused progressive increases and decreases in blood pressure (BP) and heart rate (HR) respectively. Subsequent i.v. ethanol (0.25 or 1 g.kg(-1)) elicited dose-related changes in BP (decreases) and HR (increases). These effects were replicated after intracisternal (i.c.) administration of ethanol. Blockade of nicotinic cholinoceptors (nAChR, hexamethonium, 20 mg.kg(-1)) or alpha(1)-adrenoceptors (prazosin, 1 mg.kg(-1)) attenuated cardiovascular effects of ethanol. Ethanol hypotension was also attenuated after the centrally acting sympatholytic drug moxonidine (selective I(1)-site agonist, 100 microg.kg(-1) i.v.), but not guanabenz (selective alpha(2)-receptor agonist, 30 microg.kg(-1), i.v.), suggesting involvement of central circuits of I(1) sites in ethanol-evoked hypotension. Selective blockade I(1) sites (efaroxan) but not alpha(2) (yohimbine) adrenoceptors abolished the hypotensive response to ethanol. Intracisternal administration of PD98059 or SB203580, inhibitors of extracellular signal-regulated kinase (ERK 1/2) and p38 MAPK, respectively, reduced the hypotensive action of moxonidine or ethanol. When used simultaneously, the two MAPK inhibitors produced additive attenuation of ethanol hypotension. CONCLUSIONS AND IMPLICATIONS Sympathoinhibitory pathways of central I(1)-sites and downstream ERK/p38 MAPK signalling were involved in the hypotensive action of ethanol in ARF.
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Dhalla AK, Chisholm JW, Reaven GM, Belardinelli L. A1 adenosine receptor: role in diabetes and obesity. Handb Exp Pharmacol 2009:271-295. [PMID: 19639285 DOI: 10.1007/978-3-540-89615-9_9] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Adenosine mediates its diverse effects via four subtypes (A(1), A(2A), A(2B) and A(3)) of G-protein-coupled receptors. The A(1) adenosine receptor (A(1)AR) subtype is the most extensively studied and is well characterized in various organ systems. The A(1)ARs are highly expressed in adipose tissue, and endogenous adenosine has been shown to tonically activate adipose tissue A(1)ARs. Activation of the A(1)ARs in adipocytes reduces adenylate cyclase and cAMP content and causes inhibition of lipolysis. The role of A(1)ARs in lipolysis has been well characterized by using several selective A(1)AR agonists as well as A(1)AR knockout mice. However, the contribution of A(1)ARs to the regulation of lipolysis in pathological conditions like insulin resistance, diabetes and dyslipidemia, where free fatty acids (FFA) play an important role, has not been well characterized. Pharmacological agents that reduce the release of FFA from adipose tissue and thus the availability of circulating FFA have the potential to be useful for insulin resistance and hyperlipidemia. Toward this goal, several selective and efficacious agonists of the A(1)ARs are now available, and some have entered early-phase clinical trials; however, none have received regulatory approval yet. Here we review the existing knowledge on the role of A(1)ARs in insulin resistance, diabetes and obesity, and the progress made in the development of A(1)AR agonists as antilipolytic agents, including the challenges associated with this approach.
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Affiliation(s)
- Arvinder K Dhalla
- Department of Pharmacological Sciences, CV Therapeutics Inc., Palo Alto, CA 94304, USA.
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3
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Abstract
In this review we outline the unique effects of the autacoid adenosine in the kidney. Adenosine is present in the cytosol of renal cells and in the extracellular space of normoxic kidneys. Extracellular adenosine can derive from cellular adenosine release or extracellular breakdown of ATP, AMP, or cAMP. It is generated at enhanced rates when tubular NaCl reabsorption and thus transport work increase or when hypoxia is induced. Extracellular adenosine acts on adenosine receptor subtypes in the cell membranes to affect vascular and tubular functions. Adenosine lowers glomerular filtration rate (GFR) by constricting afferent arterioles, especially in superficial nephrons, and acts as a mediator of the tubuloglomerular feedback, i.e., a mechanism that coordinates GFR and tubular transport. In contrast, it leads to vasodilation in deep cortex and medulla. Moreover, adenosine tonically inhibits the renal release of renin and stimulates NaCl transport in the cortical proximal tubule but inhibits it in medullary segments including the medullary thick ascending limb. These differential effects of adenosine are subsequently analyzed in a more integrative way in the context of intrarenal metabolic regulation of kidney function, and potential pathophysiological consequences are outlined.
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Affiliation(s)
- Volker Vallon
- Department of Medicine, University of California, San Diego, USA
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Matsuya T, Takamatsu H, Murakami Y, Noda A, Ichise R, Awaga Y, Nishimura S. Synthesis and evaluation of [11C]FR194921 as a nonxanthine-type PET tracer for adenosine A1 receptors in the brain. Nucl Med Biol 2005; 32:837-44. [PMID: 16253808 DOI: 10.1016/j.nucmedbio.2005.06.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Revised: 05/31/2005] [Accepted: 06/09/2005] [Indexed: 11/18/2022]
Abstract
This report describes the synthesis of [11C]2-(1-methyl-4-piperidinyl)-6-(2-phenylpyrazolo[1,5-a]pyridin-3-yl)-3(2H)-pyridazinone ([11C]FR194921), a highly selective, nonxanthine-type adenosine A(1) receptor antagonist, used in brain imaging in rats and conscious monkeys as a potential novel PET tracer. [11C]FR194921 was successfully synthesized in 19 min after [11C]CH3I formation. The radiochemical yield was 38+/-3%; and radioactivity was 4.1+/-0.4 GBq, calculated from end of synthesis; radiochemical purity was higher than 99%; and the specific radioactivity was 25.0+/-8.1 GBq micromol(-1) (n=5). In a rat experiment, the distribution of [11C]FR194921 was higher in the hippocampus, striatum and cerebellum regions. This accumulation was significantly decreased by approximately 50% by pretreatment with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), an adenosine A1 receptor antagonist, which indicated specific binding of the radioligand to adenosine A1 receptors. In conscious monkey PET experiments, [11C]FR194921 accumulated in several regions of the brain, especially in the occipital cortex, thalamus and striatum. These results suggest that [11C]FR194921 can be used as an agent for imaging adenosine A1 receptors in vivo by positron emission tomography (PET).
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Affiliation(s)
- Takahiro Matsuya
- Basic Research Division, The Medical and Pharmacological Research Center Foundation, Ishikawa 925-0613, Japan.
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5
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Hammond LC, Bonnet C, Kemp PJ, Yates MS, Bowmer CJ. Chronic hypoxia up-regulates expression of adenosine A1 receptors in DDT1-MF2 cells. Biochem Pharmacol 2004; 67:421-6. [PMID: 15037194 DOI: 10.1016/j.bcp.2003.09.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2003] [Accepted: 09/04/2003] [Indexed: 11/18/2022]
Abstract
As the first step to understand how chronic hypoxia might regulate smooth muscle function in health and disease, we have employed an established immortalised cell model of smooth muscle, DDT1-MF2 cells, to address the hypothesis that adenosine A1 receptor density is modulated by O2 availability. Maximal specific binding (Bmax) of the selective adenosine A1 receptor antagonist, [3H]-DPCPX, to cell membranes increased 3.5-fold from 0.48 +/- 0.02 pmol/mg to 1.7 +/- 0.5 pmol/mg protein after 16 hr of hypoxia and this effect was not accompanied by any statistically significant changes in either binding affinity (0.84 +/- 0.2 nM vs. 1.2 +/- 0.3 nM) or Hill coefficient (1.1 +/- 0.1 vs. 0.99 +/- 0.03). Hypoxia-evoked increases in membrane receptor density were paralleled in intact DDT1-MF2 cells. In addition, the increase in [3H]-DPCPX binding to intact cells was inhibited by co-incubation during hypoxia with the translational inhibitor cycloheximide, the transcriptional blocker actinomycin D and the NFkappaB inhibitor sulphasalazine. Together, these data show that adenosine A1 receptor density is modulated, at least in part, by O2-dependent activation of the transcription factor NFkappaB and adds to the list of processes dynamically regulated by ambient oxygen availability. Since hypoxia is an initiating factor in acute renal failure, similar changes in transcription may account for up-regulation of adenosine A1 receptors noted previously in the renal vasculature of rats with acute renal failure.
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Affiliation(s)
- Lucy C Hammond
- School of Biomedical Sciences, Worsley Building, University of Leeds, Leeds LS2 9JT, UK
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6
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Küçükhüseyin C, Akbaş N, Silan C, Barlas A, Yillar DO, Seçkin I. Renovascular actions of adenosine in the isolated perfused rat kidney: possible underlying mechanisms. J Basic Clin Physiol Pharmacol 2002; 12:289-304. [PMID: 11868905 DOI: 10.1515/jbcpp.2001.12.4.289] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We studied the renovascular action of adenosine on isolated perfused rat 10 min after drug injections. Adenosine was applied intraarterially as a single bolus injection in logarithmically increasing doses (0.3-30 microg). Adenosine treatment induced a biphasic vascular-response, namely, an initial vasoconstriction followed by a long-lasting vasodilation. Pretreatment with 0.1. 0.3, or 1.0 mM theophylline or quinidine (2 microg/ml) significantly depressed both components of the adenosine response. The vasoconstrictor response to adenosine was not affected by either 0.5 or 1.0 microg/ml dihydroergocristine. whereas the vasodilatory response was dose-dependently reduced. The biphasic response to adenosine was markedly depressed by 10 microg/ml indomethacin and was augmented by combining this agent with quinidine. We studied the possible roles of the platelet activating factor (PAF) and nitric oxide-cGMP systems in the renovascular actions of adenosine. Tebokan (a PAF antagonist) antagonized both components of the response, but methylene blue (MM) reduced only the pressory part Electron-microscopic examination of kidneys exposed for 15 min to MM showed some acute degenerative alterations and constriction in the glomeruli. From these findings, we conclude that the P1/A1, and P2x purinoceptors, the prostaglandins, PAF, and the NO-cGMP systems have a share in the renovascular actions of adenosine.
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Affiliation(s)
- C Küçükhüseyin
- Department of Pharmacology, Cerrahpaşa Medical Faculty, University of Istanbul, Turkey.
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7
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Docherty NG, Pérez-Barriocanal F, Balboa NE, López-Novoa JM. Transforming growth factor-beta1 (TGF-beta1): a potential recovery signal in the post-ischemic kidney. Ren Fail 2002; 24:391-406. [PMID: 12212820 DOI: 10.1081/jdi-120006767] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
TGF-beta1 has been demonstrated to be up-regulated in response to ischemic events both in animal models and in man. Demonstration of this up-regulation in the kidney following experimentally induced acute renal failure and in renal transplants complements similar findings in coronary and cerebral ischemia. Activation of TGF-beta1 occurs as a direct consequence of hypoxia, angiotensin II signaling and loss of extra cellular matrix (ECM) integrity, all of which occur in renal ischemia-reperfusion injury. TGF-beta1 thus up-regulates the synthesis of extracellular matrix components such as fibronectin and collagen IV providing a basis for the restoration of epithelial coverage in the regenerating tubule. TGF-beta1 also regulates epithelial tubular cell proliferation and differentiation. This response is quickly closed down in response to recovery of the kidney. This review examines the evidence linking TGF-beta1 activity to recovery from renal ischemia thereby constructing a hypothesis for the beneficial role of TGF-beta1 in the post ischemic kidney.
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Affiliation(s)
- Neil G Docherty
- Instituto Reina Sofia de Investigación Nefrológia, Department of Physiology and Pharmacology, University of Salamanca, Spain
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8
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Jackson EK, Zhu C, Tofovic SP. Expression of adenosine receptors in the preglomerular microcirculation. Am J Physiol Renal Physiol 2002; 283:F41-51. [PMID: 12060585 DOI: 10.1152/ajprenal.00232.2001] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to systematically investigate the abundance of each of the adenosine receptor subtypes in the preglomerular microcirculation vs. other vascular segments and vs. the renal cortex and medulla. Rat preglomerular microvessels (PGMVs) were isolated by iron oxide loading followed by magnetic separation. For comparison, mesenteric microvessels, segments of the aorta (thoracic, middle abdominal, and lower abdominal), renal cortex, and renal medulla were obtained by dissection. Adenosine receptor protein and mRNA expression were examined by Western blotting, Northern blotting, and RT-PCR. Our results indicate that compared with other vascular segments and renal tissues, A1 and A2B receptor protein and mRNA are abundantly expressed in the preglomerular microcirculation, whereas A2A and A3 receptor protein and mRNA are barely detectable or undetectable in PGMVs. We conclude that, relative to other vascular and renal tissues, A1 and A2B receptors are well expressed in PGMVs, whereas A2A and A3 receptors are notably deficient. Thus A1 and A2B receptors, but not A2A or A3 receptors, may importantly regulate the preglomerular microcirculation.
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Affiliation(s)
- Edwin K Jackson
- Center for Clinical Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA. ejd+@pitt.edu
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Smith JA, Sivaprasadarao A, Munsey TS, Bowmer CJ, Yates MS. Immunolocalisation of adenosine A(1) receptors in the rat kidney. Biochem Pharmacol 2001; 61:237-44. [PMID: 11163338 DOI: 10.1016/s0006-2952(00)00532-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The location of adenosine A(1) receptors in the rat kidney was investigated using immunolabelling with antibodies raised to a 15-amino-acid sequence near the C-terminus of the receptor (antibody I) and to a 14-amino-acid sequence in the second extracellular loop (antibody II). In the cortex, antibody I bound to adenosine A(1) receptors in mesangial cells and afferent arterioles, whilst antibody II bound to receptors in proximal convoluted tubules. In the medulla, both antibodies bound to receptors in collecting ducts and the papillary surface epithelium. These observations provide support for the diverse functional roles previously proposed for the adenosine A(1) receptor in the kidney. The labelling of distinct but different structures in the cortex by antibodies raised to different amino acid sequences on the A(1) receptor protein suggests that differing forms of the receptor are present in this region of the kidney.
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Affiliation(s)
- J A Smith
- School of Biomedical Sciences, University of Leeds, LS2 9JT, Leeds, UK
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Pflueger A, Larson TS, Nath KA, King BF, Gross JM, Knox FG. Role of adenosine in contrast media-induced acute renal failure in diabetes mellitus. Mayo Clin Proc 2000; 75:1275-83. [PMID: 11126837 DOI: 10.4065/75.12.1275] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Increased release of renal adenosine and stimulation of renal adenosine receptors have been proposed to be major mechanisms in the development of contrast media-induced acute renal failure (CM-ARF). Patients with diabetes mellitus or preexisting renal disease who have reduced renal function have a markedly increased risk to develop CM-ARF. This increased risk to develop CM-ARF in patients with diabetes mellitus is linked to a higher sensitivity of the renal vasculature to adenosine, since experimental studies have shown increased adenosine-induced vasoconstriction in the kidneys of diabetic animals. Furthermore, recent evidence suggests that administration of adenosine receptor antagonists reduces the risk of development of CM-ARF in both diabetic and nondiabetic patients. The purpose of this review is to discuss the role of adenosine in the development of CM-ARF, particularly in the kidneys of diabetic patients, and to evaluate the therapeutic potential of adenosine receptor antagonists in the prevention of CM-ARF. Selective adenosine A1 receptor antagonists may provide a therapeutic tool to prevent CM-ARF in patients with diabetes mellitus and reduced renal function.
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Affiliation(s)
- A Pflueger
- Department of Physiology and Biophysics, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
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Smith JA, Whitaker EM, Bowmer CJ, Yates MS. Differential expression of renal adenosine A(1) receptors induced by acute renal failure. Biochem Pharmacol 2000; 59:727-32. [PMID: 10677590 DOI: 10.1016/s0006-2952(99)00369-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The distribution of renal adenosine A(1) receptors was investigated in rats with glycerol- or mercuric chloride (HgCl(2))-induced acute renal failure. Receptors were localised by autoradiography using [(3)H]8-cyclopentyl-1,3-dipropylxanthine ([(3)H]DPCPX), a selective A(1) adenosine receptor antagonist. In saline-injected control animals, significant labelling with [(3)H]DPCPX was detected in glomeruli, the inner stripe of outer medulla, and the inner medulla. Sixteen hours following induction of glycerol-induced acute renal failure (ARF), a 34% increase in labelling in glomeruli was noted compared to saline-injected controls, and by 48 hr, glomerular labelling had increased by 200%. In addition, 48 hr following glycerol injection, significant labelling was now detected in the cortical labyrinth and medullary rays whilst, in the inner medulla, labelling had decreased by 34%. By contrast to glycerol-induced ARF, the only significant change noted 48 hr following induction of HgCl(2)-induced ARF was a 39% decrease in labelling in the inner medulla. It is concluded that glycerol-induced ARF results in differential expression of renal adenosine A(1) receptors with increased expression in the cortex and reduced expression in the inner medulla. Increased density of A(1) receptors in glomeruli may account, at least in part, for the increased renal vasoconstrictor response to adenosine and depressed glomerular filtration rate noted previously in this type of acute renal failure.
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Affiliation(s)
- J A Smith
- School of Biomedical Sciences, University of Leeds, Leeds, UK
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Halimi G, Sampol J, Clot-Faybesse O, Mercier L, Devaux C, Berland Y, Dussol B, Rochat H, Guieu R. Cyclosporine A and purinergic receptors in rat kidney. Life Sci 2000; 65:2801-13. [PMID: 10622269 DOI: 10.1016/s0024-3205(99)00549-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previous reports have demonstrated that Cyclosporine A (CyA) chronically administered induces an increase in adenosine plasma concentration by inhibiting adenosine uptake by red blood cells (RBC). We hypothesized that this effect may modulate, by a down regulation, the mRNA expression of adenosine receptors in rat kidney. Since high blood pressure (HBP) is a classical side effect of CyA treatment, nicardipine, a dihydropyridine calcium channel blocker, is often associated with CyA in treatment. To distinguish between the effects of CyA-induced HBP and the effects of CyA by itself, we have evaluated the effects of CyA and/or nicardipine on the mRNA expression of A1 and A2a adenosine receptors. The study was performed on five groups of rats (n= 8) receiving during 21 days either serum saline (0.5 ml i.p), CyA (12 mg/kg/day, i.p), nicardipine (1.2 mg/kg i.p) or nicardipine + CyA. The last (or fifth) group was injected with vehicle (0.5 ml i.p). Blood samples for adenosine assay were collected in the renal artery at day 21, just before the rat kidneys were removed for quantitation of adenosine A1 and A2a mRNA concentration by RT-PCR. We make two conclusions :i) Nicardipine induces a decrease in mRNA expression of A1 but not of A2a adenosine receptors. However, because nicardipine lowered both blood pressure and A1 mRNA expression, it is not possible to conclude if A1 mRNA decrease is implicated in the nicardipine effects on blood pressure.ii) CyA induces an increase in renal artery adenosine concentration and a decrease in mRNA expression of A1 and A2a adenosine receptors.
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Affiliation(s)
- G Halimi
- UMR CNRS 6560 Laboratoire de Biochimie et d'Ingenierie des Protéines, Faculté de Médecine Secteur Nord, Marseille, France
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13
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Abstract
Recent studies indicate a widening role for adenosine receptors in many therapeutic areas. Adenosine receptors are involved in immunological and inflammatory responses, respiratory regulation, the cardiovascular system, the kidney, various CNS-mediated events including sleep and neuroprotection, as well as central and peripheral pain processes. In this review, the physiological role of adenosine receptors in these key areas is described with reference to the therapeutic potential of adenosine receptor agonists and antagonists.
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Affiliation(s)
- SM Kaiser
- AstraZeneca R & D Griffith University, Brisbane 4111, Australia
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14
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Smith JA, Whitaker EM, Yaktubay N, Morton MJ, Bowmer CJ, Yates MS. Regulation of renal adenosine A(1) receptors: effect of dietary sodium chloride. Eur J Pharmacol 1999; 384:71-9. [PMID: 10611422 DOI: 10.1016/s0014-2999(99)00661-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The influence of dietary NaCl on the regulation of renal adenosine A(1) receptors was investigated in the rat. Renal membranes from rats fed on a diet low (0.04%) in NaCl showed a 46% increase in B(max) for the binding of [3H]-1,3-dipropyl-8-cyclopentylxanthine ([3H]DPCPX), a selective adenosine A(1) receptor antagonist, compared to membranes from rats fed on a normal diet (0.4% NaCl). Conversely, a high NaCl diet (4.0%) resulted in a 37% decrease in B(max). Levels of renal adenosine A(1) receptor mRNA were 65% lower in rats on a high salt diet. Autoradiographic studies showed that, for the inner medullary collecting ducts, a low NaCl diet resulted in a 30% increase in [3H]DPCPX binding with a 39% decrease noted in rats maintained on a high salt diet. The results indicate that changes in adenosine A(1) receptor density may represent a novel mechanism whereby the kidneys adapt to changes in salt load.
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Affiliation(s)
- J A Smith
- School of Biomedical Sciences, Worsley Medical and Dental Building, University of Leeds, Leeds, UK
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15
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Siniscalchi A, Rodi D, Gessi S, Campi F, Borea PA. Early changes in adenosine A1 receptors in cerebral cortex slices submitted to in vitro ischemia. Neurochem Int 1999; 34:517-22. [PMID: 10402227 DOI: 10.1016/s0197-0186(99)00028-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The effects of brain ischemia on the maximum binding capacity (Bmax) and affinity (Kd) of A1 receptors were studied in the rat cerebral cortex, with an in vitro approach. The results were correlated with changes in 3H-adenosine release, studied under identical experimental conditions. Fifteen minutes of in vitro 'ischemia' (hypoxic, glucose-free medium) induced a significant increase in both Bmax (2398+/-132 fmol/mg protein, 151% of the control, P < 0.05) and in Kd (2.43+/-0.12 nM, 161% of the control, P < 0.01). At the same time, an increase in tritium efflux from [3H]-adenosine labeled cerebral cortex slices to 324% of the control was observed. A trend toward normalization was evident 5-15 min after 'reoxygenation' (restoring normal medium), but the binding parameters were still altered after 60 min (Bmax 2110+/-82 fmol/mg protein, Kd 2.26+/-0.14 nM, P < 0.01 vs the corresponding control) as was adenosine release (196% of the control). These findings suggest that the increased availability of adenosine and its receptors may be a defense mechanism against ischemic injury, while the reduced affinity of A1 receptors, possibly due to desensitization, may be a sign of ischemia-induced cellular damage.
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Affiliation(s)
- A Siniscalchi
- Department of Clinical and Experimental Medicine, University of Ferrara, Italy.
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Nyce JW. Insight into adenosine receptor function using antisense and gene-knockout approaches. Trends Pharmacol Sci 1999; 20:79-83. [PMID: 10101969 DOI: 10.1016/s0165-6147(99)01305-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The extensive role of adenosine in discriminating input from the extracellular environment is effected through a series of cell membrane-spanning proteins--the adenosine A1, A2A, A2B and A3 receptors. New genetic and epigenetic tools have emerged that facilitate the elucidation of the function of these receptors with greater specificity than is generally possible with traditional antagonist drugs. These tools include antisense oligonucleotides (epigenetic) and gene 'knockin' and 'knockout' mice (genetic) and are discussed in this article by Jonathan Nyce.
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Affiliation(s)
- J W Nyce
- Department of Molecular Pharmacology and Therapeutics, EpiGenesis Pharmaceuticals, Princeton, NJ 08543, USA
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Morton MJ, Sivaprasadarao A, Bowmer CJ, Yates MS. Adenosine receptor mRNA levels during postnatal renal maturation in the rat. J Pharm Pharmacol 1998; 50:649-54. [PMID: 9680076 DOI: 10.1111/j.2042-7158.1998.tb06900.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Adenosine may affect the pattern of intrarenal blood flow during renal development. It provides an angiogenic stimulus for the growth of new blood vessels and may be involved in compensatory renal growth. It is therefore of interest to investigate the expression of adenosine receptor genes during postnatal renal development. In the present study this was carried out by measuring adenosine receptor mRNA levels in rats aged between 2 and 60 days. The order of abundance of adenosine receptor mRNA levels in 60-day-old rats was A2A > A2B > or = A1 > A3. A1 receptor mRNA levels showed only small changes with increasing age although, by contrast, A3 receptor mRNA increased markedly with age with levels at 60 days twenty-fold greater than at 2 days. A2A receptor mRNA levels declined during renal maturation with transcript numbers four- to fivefold that at 12-18 days compared with numbers at 60 days. By contrast to the A2A receptor, there were no significant changes in the renal levels of A2B receptor mRNA during kidney maturation. During postnatal renal maturation, the levels of mRNA for A2A and A3 adenosine receptor subtypes undergo marked changes which may be related to functional maturation, morphological development, or both.
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Affiliation(s)
- M J Morton
- Department of Pharmacology, Worsley Medical and Dental Building, University of Leeds, UK
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