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Mechanisms for the α-Adrenoceptor-Mediated Positive Inotropy in Mouse Ventricular Myocardium: Enhancing Effect of Action Potential Prolongation. Int J Mol Sci 2023; 24:ijms24043926. [PMID: 36835338 PMCID: PMC9964142 DOI: 10.3390/ijms24043926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 02/09/2023] [Accepted: 02/13/2023] [Indexed: 02/17/2023] Open
Abstract
Mechanisms for the α-adrenoceptor-mediated positive inotropy in neonatal mouse ventricular myocardium were studied with isolated myocardial preparations. The phenylephrine-induced positive inotropy was suppressed by prazosin, nifedipine, and chelerythrine, a protein kinase C inhibitor, but not by SEA0400, a selective Na+/Ca2+ exchanger inhibitor. Phenylephrine increased the L-type Ca2+ channel current and prolonged the action potential duration, while the voltage-dependent K+ channel current was not influenced. In the presence of cromakalim, an ATP-sensitive K+ channel opener, the phenylephrine-induced prolongation of action potential duration, as well as the positive inotropy, were smaller than in the absence of cromakalim. These results suggest that the α-adrenoceptor-mediated positive inotropy is mediated by an increase in Ca2+ influx through the L-type Ca2+ channel, and the concomitant increase in action potential duration acts as an enhancing factor.
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Erdogan BR, Michel MC, Arioglu-Inan E. Expression and Signaling of β-Adrenoceptor Subtypes in the Diabetic Heart. Cells 2020; 9:cells9122548. [PMID: 33256212 PMCID: PMC7759850 DOI: 10.3390/cells9122548] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 11/20/2020] [Accepted: 11/24/2020] [Indexed: 12/18/2022] Open
Abstract
Diabetes is a chronic, endocrine disorder that effects millions of people worldwide. Cardiovascular complications are the major cause of diabetes-related morbidity and mortality. Cardiac β1- and β2-adrenoceptor (AR) stimulation mediates positive inotropy and chronotropy, whereas β3-AR mediates negative inotropic effect. Changes in β-AR responsiveness are thought to be an important factor that contributes to the diabetic cardiac dysfunction. Diabetes related changes in β-AR expression, signaling, and β-AR mediated cardiac function have been studied by several investigators for many years. In the present review, we have screened PubMed database to obtain relevant articles on this topic. Our search has ended up with wide range of different findings about the effect of diabetes on β-AR mediated changes both in molecular and functional level. Considering these inconsistent findings, the effect of diabetes on cardiac β-AR still remains to be clarified.
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Affiliation(s)
- Betul R. Erdogan
- Department of Pharmacology, Faculty of Pharmacy, Ankara University, 06560 Ankara, Turkey;
- Department of Pharmacology, Faculty of Pharmacy, Izmir Katip Celebi University, 35620 Izmir, Turkey
| | - Martin C. Michel
- Department of Pharmacology, Johannes Gutenberg University, 55131 Mainz, Germany;
| | - Ebru Arioglu-Inan
- Department of Pharmacology, Faculty of Pharmacy, Ankara University, 06560 Ankara, Turkey;
- Correspondence:
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Kanae H, Hamaguchi S, Wakasugi Y, Kusakabe T, Kato K, Namekata I, Tanaka H. Pathological prolongation of action potential duration as a cause of the reduced alpha-adrenoceptor-mediated negative inotropy in streptozotocin-induced diabetic mice myocardium. J Pharmacol Sci 2017; 135:131-133. [DOI: 10.1016/j.jphs.2017.10.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 10/09/2017] [Accepted: 10/12/2017] [Indexed: 10/18/2022] Open
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NOS1 induces NADPH oxidases and impairs contraction kinetics in aged murine ventricular myocytes. Basic Res Cardiol 2015; 110:506. [PMID: 26173391 DOI: 10.1007/s00395-015-0506-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 06/20/2015] [Accepted: 07/07/2015] [Indexed: 01/08/2023]
Abstract
Nitric oxide (NO) modulates calcium transients and contraction of cardiomyocytes. However, it is largely unknown whether NO contributes also to alterations in the contractile function of cardiomyocytes during aging. Therefore, we analyzed the putative role of nitric oxide synthases and NO for the age-related alterations of cardiomyocyte contraction. We used C57BL/6 mice, nitric oxide synthase 1 (NOS1)-deficient mice (NOS1(-/-)) and mice with cardiomyocyte-specific NOS1-overexpression to analyze contractions, calcium transients (Indo-1 fluorescence), acto-myosin ATPase activity (malachite green assay), NADPH oxidase activity (lucigenin chemiluminescence) of isolated ventricular myocytes and cardiac gene expression (Western blots, qPCR). In C57BL/6 mice, cardiac expression of NOS1 was upregulated by aging. Since we found a negative regulation of NOS1 expression by cAMP in isolated cardiomyocytes, we suggest that reduced efficacy of β-adrenergic signaling that is evident in aged hearts promotes upregulation of NOS1. Shortening and relengthening of cardiomyocytes from aged C57BL/6 mice were decelerated, but were normalized by pharmacological inhibition of NOS1/NO. Cardiomyocytes from NOS1(-/-) mice displayed no age-related changes in contraction, calcium transients or acto-myosin ATPase activity. Aging increased cardiac expression of NADPH oxidase subunits NOX2 and NOX4 in C57BL/6 mice, but not in NOS1(-/-) mice. Similarly, cardiac expression of NOX2 and NOX4 was upregulated in a murine model with cardiomyocyte-specific overexpression of NOS1. We conclude that age-dependently upregulated NOS1, putatively via reduced efficacy of β-adrenergic signaling, induces NADPH oxidases. By increasing nitrosative and oxidative stress, both enzyme systems act synergistically to decelerate contraction of aged cardiomyocytes.
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Shpakov AO, Derkach KV, Chistyakova OV, Moyseyuk IV, Bondareva VM. The effect of long-term diabetes mellitus induced by treatment with streptozotocin in 6-week-old rats on functional activity of the adenylyl cyclase system. ACTA ACUST UNITED AC 2014. [DOI: 10.1134/s1990519x14010118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Ceylan-Isık A, Hünkar T, Aşan E, Kaymaz F, Arı N, Söylemezoǧlu T, Renda N, Soncul H, Bali M, Karasu Ç. Cod liver oil supplementation improves cardiovascular and metabolic abnormalities in streptozotocin diabetic rats. J Pharm Pharmacol 2010; 59:1629-41. [DOI: 10.1211/jpp.59.12.0004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Abstract
Abnormalities in the metabolism of essential fatty acids and the results of increased oxidative stress have been implicated in cardiovascular disorders observed in diabetes mellitus. This study, therefore, aimed to investigate the effects of cod liver oil (CLO, Lysi Ltd, Iceland), which comprises mainly an antioxidant vitamin A, n:3 polyunsaturated fatty acids (n:3 PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on cardiovascular abnormalities in streptozotocin (STZ)-diabetic rats. Two days after single STZ (55 mg kg−1, i.p.) or vehicle injection, diabetes was verified by increased blood glucose, and non-diabetic and diabetic rats were left untreated or treated with CLO (0.5 mL kg−1 daily, by intragastric probing) for 12 weeks. Plasma glucose, triacylglycerol and cholesterol concentrations were significantly elevated in 12-week untreated-diabetic rats; CLO provided better weight gain, entirely prevented the plasma lipid abnormalities, but partially controlled the glycaemia in diabetic rats. In isolated aorta rings, diabetes resulted in increased phenylephrine-induced vasoconstriction and isoprenaline-induced vasorelaxation, impaired endothelium-dependent vasodilatation and unchanged responsiveness to sodium nitroprusside. CLO treatment completely prevented endothelial deficiency, partly corrected the phenylephrine-induced vasoconstriction and did not affect the responses to isoprenaline and sodium nitroprusside in diabetic aorta. Diabetes also produced a marked decrease in the rate of spontaneously beating right atria and a significant increase in basal contractile force of left ventricular papillary muscle. The responsiveness of right atria to the positive chronotropic effect of isoprenaline was significantly decreased in diabetic rats, and was increased in CLO-treated diabetic rats. The positive chronotropic effect of noradrenaline was markedly increased in diabetic atria, but prevented by CLO treatment. Diabetes also resulted in an increased positive inotropic response of papillary muscle to both noradrenaline and isoprenaline, which were prevented by CLO treatment. CLO treatment also resulted in lower tissue sensitivity (pD2) to these agonists in diabetic papillary muscle. Ventricular hydroxy-proline content was found to be unchanged among the experimental groups. The ultrastructure of diabetic myocardium displayed various degenerations (i.e. intracellular oedema, myofibrillar fragmentation, condensed pleomorphic mitochondria, thick capillary irregular basement membrane, swollen endothelial cells), which were partially prevented by CLO treatment. We conclude that the supplementation with CLO is effective in preventing cardiovascular disorders observed in experimental diabetes.
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Affiliation(s)
- Aslı Ceylan-Isık
- Department of Pharmacology, Faculty of Pharmacy, Ankara University, Ankara, Turkey
| | - Tuǧba Hünkar
- Institute of Forensic Medicine, Ankara University, Ankara, Turkey
| | - Esin Aşan
- Department of Histology and Embryology, Hacettepe University, Ankara, Turkey
| | - Fugen Kaymaz
- Department of Histology and Embryology, Hacettepe University, Ankara, Turkey
| | - Nuray Arı
- Department of Pharmacology, Faculty of Pharmacy, Ankara University, Ankara, Turkey
| | | | - Nurten Renda
- Department of Biochemistry, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Halim Soncul
- Department of Nephrology, Faculty of Medicine, Gazi University, Ankara, Turkey
| | - Musa Bali
- Department of Cardiovascular Surgery, Faculty of Medicine, Gazi University, Ankara, Turkey
| | - Çimen Karasu
- Department of Medical Pharmacology, Faculty of Medicine, Gazi University, Ankara, Turkey
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7
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Mechanisms of α1-adrenoceptor mediated QT prolongation in the diabetic rat heart. Life Sci 2009; 84:250-6. [DOI: 10.1016/j.lfs.2008.12.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2008] [Revised: 11/14/2008] [Accepted: 12/06/2008] [Indexed: 11/23/2022]
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Aragno M, Mastrocola R, Alloatti G, Vercellinatto I, Bardini P, Geuna S, Catalano MG, Danni O, Boccuzzi G. Oxidative stress triggers cardiac fibrosis in the heart of diabetic rats. Endocrinology 2008; 149:380-8. [PMID: 17901230 DOI: 10.1210/en.2007-0877] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Diabetic cardiomyopathy is characterized by myocyte loss and myocardial fibrosis, leading to decreased elasticity and impaired contractile function. The study examines the downstream signaling whereby oxidative stress, induced by hyperglycemia, leads to myocardial fibrosis and impaired contractile function in the left ventricle of diabetic rats. It also examines the effects of dehydroepiandrosterone (DHEA), which prevents the oxidative damage induced by hyperglycemia in experimental models. DHEA was administered for 6 wk in the diet [0.02%, wt/wt)] to rats with streptozotocin-induced diabetes. Oxidative balance, advanced glycated end products (AGEs) and AGE receptors, transcription factors nuclear factor-kappaB and activator protein-1, and profibrogenic growth factors (connective tissue growth factor and TGFbeta1) were determined in the left ventricle of treated and untreated streptozotocin-diabetic rats. Structural and ultrastructural changes, and the contractile force developed by electrically driven papillary muscles, under basal conditions and after stimulation with isoproterenol, were also evaluated. Oxidative stress induced by hyperglycemia increased AGEs and AGE receptors and triggered a cascade of signaling, eventually leading to interstitial fibrosis. DHEA treatment, by improving oxidative balance, counteracted the enhanced AGE receptor activation and increase of profibrogenic factors and restored tissue levels of collagen I, collagen IV, and fibronectin to those of control animals. Moreover, DHEA completely restored the contractility of isolated papillary muscle. Oxidative stress led to cardiac fibrosis, the most important pathogenetic factor of the heart's impaired functional integrity in diabetes. Structural and ultrastructural changes and impairment of muscle function induced by experimental diabetes were minimized by DHEA treatment.
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MESH Headings
- Animals
- Connective Tissue Growth Factor
- Dehydroepiandrosterone/pharmacology
- Dehydroepiandrosterone/therapeutic use
- Diabetes Mellitus, Experimental/complications
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Drug Evaluation, Preclinical
- Fibrosis
- Gene Expression Regulation/drug effects
- Glycation End Products, Advanced/metabolism
- Heart Diseases/drug therapy
- Heart Diseases/etiology
- Heart Diseases/metabolism
- Heart Diseases/pathology
- Heart Ventricles/metabolism
- Heart Ventricles/pathology
- Immediate-Early Proteins/genetics
- Immediate-Early Proteins/metabolism
- Intercellular Signaling Peptides and Proteins/genetics
- Intercellular Signaling Peptides and Proteins/metabolism
- Male
- Myocardium/pathology
- Myocardium/ultrastructure
- Oxidative Stress/drug effects
- Oxidative Stress/physiology
- Rats
- Rats, Wistar
- Receptor for Advanced Glycation End Products
- Receptors, Adrenergic, beta-1/genetics
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Immunologic/metabolism
- Streptozocin
- Transcription Factor AP-1/metabolism
- Transforming Growth Factor beta1/genetics
- Transforming Growth Factor beta1/metabolism
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Affiliation(s)
- Manuela Aragno
- Department of Experimental Medicine and Oncology, University of Turin, Via Genova 3, 10126 Turin, Italy
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9
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Kamata K, Satoh T, Matsumoto T, Noguchi E, Taguchi K, Kobayashi T, Tanaka H, Shigenobu K. Enhancement of methoxamine-induced contractile responses of rat ventricular muscle in streptozotocin-induced diabetes is associated with alpha1A adrenoceptor upregulation. Acta Physiol (Oxf) 2006; 188:173-83. [PMID: 17054657 DOI: 10.1111/j.1748-1716.2006.01616.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
AIM To clarify the time-related changes in cardiac function and the mechanism underlying the cardiac dysfunction present in diabetes mellitus, we studied mechanical responses induced by alpha(1)- and beta-adrenoceptors, the Ca(2+)-entry promoter Bay K 8644- and ryanodine (an agent known to inhibit Ca(2+) release from the sarcoplasmic reticulum) in papillary muscles from streptozotocin (STZ)-induced diabetic and age-matched control rats. METHODS Male Wistar rats received a single injection of STZ (60 mg kg(-1)) via the tail vein to induce diabetes. For the mechanical studies, papillary muscle preparations were suspended in an organ bath and isometric contractions were measured in 1-, 4-, and 10-week STZ-induced diabetic and age-matched control rats. RESULTS In 1-week diabetic rats, the contractions induced by isoproterenol, methoxamine and Bay K 8644 were unchanged (vs. age-matched controls). In 4-week diabetic rats, (a) the isoproterenol- and Bay K 8644-induced contractions were impaired, (b) sensitivity to ryanodine was reduced, whereas (c) the methoxamine-induced contraction was unchanged. In 10-week diabetic rats, the isoproterenol- and Bay K 8644-induced contractile responses were impaired and the sensitivity to ryanodine was reduced, but in sharp contrast the methoxamine-induced contraction was enhanced. Both the mRNA level for the alpha(1A) adrenoceptor (but not the alpha(1B) or alpha(1D) mRNAs) and alpha(1A) adrenoceptor protein were increased in 10-week diabetic rats (vs. age-matched controls). CONCLUSION These results suggest that impairments of beta-adrenergic and Ca(2+)-handling mechanisms occur early in the development of cardiomyopathy in STZ-induced diabetic rats, and that this is followed by augmentation of alpha(1A) adrenoceptor-mediated inotropy due to alpha(1A) adrenoceptor upregulation.
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Affiliation(s)
- K Kamata
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Tokyo, Japan.
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10
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Matsumoto T, Wakabayashi K, Kobayashi T, Kamata K. Functional changes in adenylyl cyclases and associated decreases in relaxation responses in mesenteric arteries from diabetic rats. Am J Physiol Heart Circ Physiol 2005; 289:H2234-43. [PMID: 15894571 DOI: 10.1152/ajpheart.00971.2004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To assess the functional change in adenylyl cyclases (AC) associated with the diabetic state, we investigated AC-mediated relaxations and cAMP production in mesenteric arteries from rats with streptozotocin (STZ)-induced diabetes. The relaxations induced by the water-soluble forskolin (FSK) analog NKH477, which is a putative AC5 activator, but not by the beta-adrenoceptor agonist isoproterenol (Iso) and the AC activator FSK, were reduced in intact diabetic mesenteric artery. In diabetic rats, however, Iso-, FSK-, and NKH477-induced relaxations were attenuated in the presence of inhibitors of nitric oxide synthase and cyclooxygenase. To exclude the influence of phosphodiesterase (PDE), we also examined the relaxations induced by several AC activators in the presence of 3-isobutyl-1-methylxanthine (IBMX; a PDE inhibitor). Under these conditions, the relaxation induced by Iso was greatly impaired in STZ-diabetic rats. This Iso-induced relaxation was significantly attenuated by pretreatment with SQ-22536, an AC inhibitor, in mesenteric rings from age-matched controls but not in those from STZ-diabetic rats. Under the same conditions, the relaxations induced by FSK or NKH477 were impaired in STZ-diabetic rats. Neither FSK- nor A-23187 (a Ca2+ ionophore)-induced cAMP production was significantly different between diabetics and controls. However, cAMP production induced by Iso or NKH477 was significantly impaired in diabetic mesenteric arteries. Expression of mRNAs and proteins for AC5/6 was lower in diabetic mesenteric arteries than in controls. These results suggest that AC-mediated relaxation is impaired in the STZ-diabetic rat mesenteric artery, perhaps reflecting a reduction in AC5/6 activity.
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Affiliation(s)
- Takayuki Matsumoto
- Dept. of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi Univ., Shinagawa-ku, Tokyo 142-8501, Japan
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Matsumoto T, Wakabayashi K, Kobayashi T, Kamata K. Diabetes-related changes in cAMP-dependent protein kinase activity and decrease in relaxation response in rat mesenteric artery. Am J Physiol Heart Circ Physiol 2004; 287:H1064-71. [PMID: 15130892 DOI: 10.1152/ajpheart.00069.2004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Using superior mesenteric artery rings isolated from age-matched controls and streptozotocin (STZ)-induced diabetic rats, we recently demonstrated that EDHF-type relaxation is impaired in STZ-induced diabetic rats, possibly due to a reduced action of cAMP via increased phosphodiesterase (PDE) activity (Matsumoto T, Kobayashi T, and Kamata K. Am J Physiol Heart Circ Physiol 285: H283-H291, 2003). Here, we investigated the activity and expression of cAMP-dependent protein kinase (PKA), an enzyme that is produced by a pleiotropic and plays key roles in the transduction of many external signals through the cAMP second messenger pathway and in cAMP-mediated vasorelaxation. The relaxation induced by cilostamide, a selective PDE3 inhibitor, was significantly weaker in superior mesenteric artery rings from STZ-induced diabetic rats than in those from age-matched controls. The relaxation responses to 8-bromo-cAMP (8Br-cAMP) and N6,O2-dibutyryl-adenosine-cAMP (db-cAMP), a cell-permeant cAMP analog, were also impaired in the STZ diabetic group. PKA activity in the db-cAMP-treated mesenteric artery was significantly lower in the STZ diabetic group. The expression levels of the mRNA and protein for PKA catalytic subunit Cat-alpha were significantly decreased in the STZ diabetic group, but those for PKA regulatory subunit isoform RII-beta were increased. We conclude that the abnormal vascular relaxation responsiveness seen in STZ-induced diabetic rats may be attributable not only to increased PDE activity but also to decreased PKA activity. Possibly, the decreased PKA activity may result from an imbalance between PKA catalytic and regulatory subunit expressions.
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Affiliation(s)
- Takayuki Matsumoto
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo 142-8501, Japan
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Pang Y, Bounelis P, Chatham JC, Marchase RB. Hexosamine pathway is responsible for inhibition by diabetes of phenylephrine-induced inotropy. Diabetes 2004; 53:1074-81. [PMID: 15047624 DOI: 10.2337/diabetes.53.4.1074] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Hyperglycemia diminishes positive inotropic responses to agonists that activate phospholipase C (PLC) and generate inositol trisphosphate (1,4,5). The mechanisms underlying both the inotropic responses and hyperglycemia's effects on them remain undetermined, but data from isolated cardiomyocytes suggest the involvement of capacitative Ca(2+) entry (CCE), the influx of Ca(2+) through plasma membrane channels activated in response to depletion of endoplasmic or sarcoplasmic reticulum Ca(2+) stores. In neonatal rat cardiomyocytes, hyperglycemia decreased CCE induced by PLC-mediated agonists. The attenuation of CCE was also seen with glucosamine, and the inhibition by hyperglycemia was prevented by azaserine, thereby implicating hexosamine biosynthesis as the responsible metabolic pathway. In the current study, the importance of hexosamine metabolites to hyperglycemia's effects on inotropic responses was examined in isolated perfused rat hearts. The inhibition by hyperglycemia of phenylephrine-induced inotropy was reversed with azaserine and mimicked by glucosamine. An independent inhibitor of CCE, SKF96365, was also effective in blunting inotropy. These treatments did not inhibit inotropy induced by activation of adenylate cyclase through beta-adrenergic receptors. These data thus implicate CCE in responses to PLC-mediated agonists in the intact heart and point to the hexosamine pathway's negative effect on CCE as being central to the inhibition seen with hyperglycemia.
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Affiliation(s)
- Yi Pang
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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13
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Sellers DJ, Chess-Williams R. The effects of streptozotocin-induced diabetes and aldose reductase inhibition with sorbinil, on left and right atrial function in the rat. J Pharm Pharmacol 2000; 52:687-94. [PMID: 10875546 DOI: 10.1211/0022357001774363] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Diabetes mellitus is frequently associated with the complications of cardiovascular disease. Activation of the aldose reductase (or polyol) pathway has long been implicated as an underlying factor for the development of many diabetic complications and indeed, treatment with aldose reductase inhibitors has been shown to prevent or reverse many of these diabetic complications. This study examines the effects of 14-day streptozotocin-induced diabetes on alpha1- and beta-adrenoceptor-mediated responses in rat isolated left and right atria. The effects of treatment with the aldose reductase inhibitor (ARI) sorbinil were also studied. A positive inotropic response was observed to both isoprenaline and phenylephrine in left atria. Diabetes of 14 days duration resulted in a supersensitivity of these tissues to the beta-adrenoceptor agonist in comparison with controls, while responses to the alpha1-adrenoceptor agonist were unaltered. Spontaneously beating right atria from diabetic rats was found to have a depressed resting rate compared with control tissues, although positive chronotropic beta-adrenoceptor-mediated responses were not affected by diabetes. Phenylephrine produced alpha1-adrenoceptor-mediated chronotropic responses in right atrial tissues, and these were found to be enhanced in rats with diabetes. Treatment of diabetic rats with the ARI sorbinil was successful in preventing only one of the observed diabetes-induced changes in atrial function, namely the supersensitivity of left atria to isoprenaline. Sorbinil treatment did, however, alter responses of control left and right atria in a manner similar to diabetes. In conclusion, streptozotocin-induced diabetes of 14 days duration was found to cause a number of alterations in the functioning of both left and right atria. ARI treatment with sorbinil failed to prevent all but one of these changes, and in addition altered responses of atria from control rats, having a similar effect to that produced by diabetes. These data suggest that sorbinil may have effects in addition to, and independent of, aldose reductase inhibition in the cardiovascular system.
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Affiliation(s)
- D J Sellers
- Department of Biomedical Science, University of Sheffield, UK
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14
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Dinçer UD, Onay A, Ari N, Ozçelikay AT, Altan VM. The effects of diabetes on beta-adrenoceptor mediated responsiveness of human and rat atria. Diabetes Res Clin Pract 1998; 40:113-22. [PMID: 9681276 DOI: 10.1016/s0168-8227(98)00034-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The literature on the influence of diabetes on cardiac beta-adrenoceptors is still a matter of controversy. Hence, in the present study, the responsiveness of spontaneously beating right atria from streptozotocin (STZ)-diabetic rats to beta-adrenoceptor agonists were compared with those from non-diabetic controls. The responsiveness of right atria from 8-week diabetic rats to the chronotropic effects of isoprenaline, noradrenaline and fenoterol was found to be unchanged. As the disease progressed, on the other hand, the diabetic atria were found to have decreased responsiveness to the chronotropic effects of noradrenaline. The pD2 value and maximum chronotropic effect of noradrenaline were decreased in 14-week diabetic right atria when compared with those from age-matched controls. A significant decrease in the maximum chronotropic response to isoprenaline with no change in pD2 value was also observed in 14-week diabetes. These results suggest that beta 1--but not beta 2-adrenoceptor mediated chronotropic responses were reduced in the right atria due to the increase in the duration of diabetes. On the other hand, the inotropic responses to beta-adrenoceptor agonists were also assessed on diabetic and nondiabetic human atrial tissue. There were no significant differences in the inotropic responses to each agonists in either of the diabetic and nondiabetic human atrial tissues. The full agonist potency order was isoprenaline > or = fenoterol > noradrenaline.
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Affiliation(s)
- U D Dinçer
- Department of Pharmacology, Faculty of Pharmacy, University of Ankara, Tandogan, Turkey
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