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de Oliveira HT, Couto GK, Davel AP, Xavier FE, Rossoni LV. Chronic cyclooxygenase-2 inhibition prevents the worsening of hypertension and endothelial dysfunction induced by ouabain in resistance arteries of spontaneously hypertensive rats. Vascul Pharmacol 2021; 139:106880. [PMID: 34052431 DOI: 10.1016/j.vph.2021.106880] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/21/2021] [Accepted: 05/25/2021] [Indexed: 01/16/2023]
Abstract
AIM Previous studies raise cyclooxygenase (COX) activation as a possible mechanism involved in the pathophysiology of ouabain-induced hypertension. We hypothesized that inhibition of COX-2 activity might prevent ouabain-induced vascular dysfunction and worsening of hypertension in spontaneously hypertensive rats (SHR). METHODS SHR were exposed to ouabain or vehicle and treated or not with the selective COX-2 inhibitor nimesulide for 5 weeks. Systolic blood pressure was measured by plethysmography. Vascular reactivity by wire myograph and protein expression by Western-blot were assessed in mesenteric resistance arteries (MRA) of groups. Thromboxane A2 (TXA2) production by ELISA was evaluated in MRA supernatants of groups. RESULTS Noradrenaline-induced maximal contraction (Emax) was greater in MRA from SHR receiving ouabain than those of vehicle group. In situ inhibition of COX-2, TXA2 synthase, or TP receptor reduced the Emax to noradrenaline in MRA of ouabain to vehicle levels. TXA2 production was higher in ouabain than in vehicle group. Ouabain enhanced expression of cytoplasmic tyrosine kinase Src (c-Src)/ERK1/2/COX-2/TXA2 synthase/TP receptor in SHR MRA, but did not change NFkB/iKB ratio. Anticontractile effect of nitric oxide (NO) was smaller in MRA from ouabain- than vehicle-treated SHR, as well as eNOS and nNOS expression. Nimesulide co-treatment prevented the ouabain-induced worsening of hypertension and noradrenaline MRA hypercontractility in SHR. CONCLUSION Ouabain worsen hypertension and induce MRA hypercontractility in SHR associated with upregulated c-Src/ERK1/2/COX-2/TXA2 synthase/TXA2/TP receptor axis. These effects were prevented by COX-2 inhibition.
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Affiliation(s)
- Helane Tito de Oliveira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, Brazil
| | - Gisele Kruger Couto
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, Brazil
| | - Ana Paula Davel
- Department of Structural and Functional Biology, University of Campinas, Campinas, Brazil
| | - Fabiano Elias Xavier
- Department of Physiology and Pharmacology, Biosciences Center, Federal University of Pernambuco, Recife, Brazil
| | - Luciana Venturini Rossoni
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, Brazil.
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2
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Luchi TC, Coelho PM, Cordeiro JP, Assis ALEM, Nogueira BV, Marques VB, Dos Santos L, Lima-Leopoldo AP, Lunz W, Leopoldo AS. Chronic aerobic exercise associated to low-dose L-NAME improves contractility without changing calcium handling in rat cardiomyocytes. ACTA ACUST UNITED AC 2020; 53:e8761. [PMID: 32159612 PMCID: PMC7076801 DOI: 10.1590/1414-431x20198761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Accepted: 12/11/2019] [Indexed: 11/22/2022]
Abstract
Nitric oxide (NO) inhibition by high-dose NG-nitro-L-arginine methyl ester (L-NAME) is associated with several detrimental effects on the cardiovascular system. However, low-dose L-NAME increases NO synthesis, which in turn induces physiological cardiovascular benefits, probably by activating a protective negative feedback mechanism. Aerobic exercise, likewise, improves several cardiovascular functions in healthy hearts, but its effects are not known when chronically associated with low-dose L-NAME. Thus, we tested whether the association between low-dose L-NAME administration and chronic aerobic exercise promotes beneficial effects to the cardiovascular system, evaluating the cardiac remodeling process. Male Wistar rats were randomly assigned to control (C), L-NAME (L), chronic aerobic exercise (Ex), and chronic aerobic exercise associated to L-NAME (ExL). Aerobic training was performed with progressive intensity for 12 weeks; L-NAME (1.5 mg·kg-1·day-1) was administered by orogastric gavage. Low-dose L-NAME alone did not change systolic blood pressure (SBP), but ExL significantly increased SBP at week 8 with normalization after 12 weeks. Furthermore, ExL promoted the elevation of left ventricle (LV) end-diastolic pressure without the presence of cardiac hypertrophy and fibrosis. Time to 50% shortening and relaxation were reduced in ExL, suggesting a cardiomyocyte contractile improvement. In addition, the time to 50% Ca2+ peak was increased without alterations in Ca2+ amplitude and time to 50% Ca2+ decay. In conclusion, the association of chronic aerobic exercise and low-dose L-NAME prevented cardiac pathological remodeling and induced cardiomyocyte contractile function improvement; however, it did not alter myocyte affinity and sensitivity to intracellular Ca2+ handling.
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Affiliation(s)
- T C Luchi
- Departamento de Desportos, Centro de Educação Física e Desportos, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - P M Coelho
- Programa de Pós-Graduação em Nutrição e Saúde, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - J P Cordeiro
- Departamento de Desportos, Centro de Educação Física e Desportos, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - A L E M Assis
- Departamento de Morfologia, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - B V Nogueira
- Departamento de Morfologia, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - V B Marques
- Departamento de Ciências Fisiológicas, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - L Dos Santos
- Departamento de Ciências Fisiológicas, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - A P Lima-Leopoldo
- Departamento de Desportos, Centro de Educação Física e Desportos, Universidade Federal do Espírito Santo, Vitória, ES, Brasil.,Programa de Pós-Graduação em Nutrição e Saúde, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - W Lunz
- Departamento de Desportos, Centro de Educação Física e Desportos, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - A S Leopoldo
- Departamento de Desportos, Centro de Educação Física e Desportos, Universidade Federal do Espírito Santo, Vitória, ES, Brasil.,Programa de Pós-Graduação em Nutrição e Saúde, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brasil
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3
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Veklich TO, Labyntseva RD, Shkrabak OA, Tsymbalyuk OV, Rodik RV, Kalchenko VI, Kosterin SO. Inhibition of Na(+),K(+)-ATPase and activation of myosin ATPase by calix[4]arene C-107 cause stimulation of isolated smooth muscle contractile activity. UKRAINIAN BIOCHEMICAL JOURNAL 2020. [DOI: 10.15407/ubj92.01.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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4
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Cordeiro ER, Filetti FM, Simões MR, Vassallo DV. Mercury induces nuclear estrogen receptors to act as vasoconstrictors promoting endothelial denudation via the PI3K/Akt signaling pathway. Toxicol Appl Pharmacol 2019; 381:114710. [PMID: 31415774 DOI: 10.1016/j.taap.2019.114710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 07/29/2019] [Accepted: 08/10/2019] [Indexed: 10/26/2022]
Abstract
Cardiovascular diseases (CVD) are more frequent among postmenopausal women due to the decline of estrogen concentration in plasma. However, the role of the vascular modulator effect of estrogen is controversial, since it occurs both in physiological and pathological conditions, increasing or reducing vascular reactivity. As mercury is widely associated with the development of CVD, we investigated putative hazardous effects on the mechanisms that modulate vascular reactivity in aortic rings of female Wistar rats promoted by acute mercury exposure. Mercury increased vascular reactivity and oxidative stress possibly due to NADPH oxidase participation, increased production of cyclooxygenase-2 (COX-2) and thromboxane A2 (TXA2) formation. The metal also induced endothelial denudation in the aorta by reducing the bioavailability of nitric oxide (NO) and enhancing the activity of the PI3K/Akt signaling pathway. Mercury exposure also induced nuclear estrogen receptors (ERα, ERβ) to act as vasoconstrictors. Our findings suggest that mercury might increase the chances of developing cardiovascular diseases in females and should be considered an important environmental risk factor.
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Affiliation(s)
- Evellyn Rodrigues Cordeiro
- Dept. of Physiological Sciences, Universidade Federal do Espírito Santo, Vitória, ES CEP 29043-900, Brazil
| | - Filipe Martinuzo Filetti
- Dept. of Physiological Sciences, Universidade Federal do Espírito Santo, Vitória, ES CEP 29043-900, Brazil
| | - Maylla Ronacher Simões
- Dept. of Physiological Sciences, Universidade Federal do Espírito Santo, Vitória, ES CEP 29043-900, Brazil
| | - Dalton Valentim Vassallo
- Dept. of Physiological Sciences, Universidade Federal do Espírito Santo, Vitória, ES CEP 29043-900, Brazil; Health Science Center of Vitória-EMESCAM, Vitória, ES CEP 29045-402, Brazil.
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5
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Marques VB, Leal MAS, Mageski JGA, Fidelis HG, Nogueira BV, Vasquez EC, Meyrelles SDS, Simões MR, dos Santos L. Chronic iron overload intensifies atherosclerosis in apolipoprotein E deficient mice: Role of oxidative stress and endothelial dysfunction. Life Sci 2019; 233:116702. [DOI: 10.1016/j.lfs.2019.116702] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/24/2019] [Accepted: 07/25/2019] [Indexed: 02/07/2023]
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6
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Botelho T, Marques VB, Simões MR, do Val Lima PR, Simões FV, Vassallo DV, dos Santos L. Impaired participation of potassium channels and Na+
/K+
-ATPase in vasodilatation due to reduced nitric oxide bioavailability in rats exposed to mercury. Basic Clin Pharmacol Toxicol 2018; 124:190-198. [DOI: 10.1111/bcpt.13113] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 08/13/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Tatiani Botelho
- Department of Physiological Sciences; Federal University of Espirito Santo; Vitória Brazil
| | - Vinícius B. Marques
- Department of Physiological Sciences; Federal University of Espirito Santo; Vitória Brazil
| | - Maylla R. Simões
- Department of Physiological Sciences; Federal University of Espirito Santo; Vitória Brazil
| | | | - Fabiana V. Simões
- Department of Physiological Sciences; Federal University of Espirito Santo; Vitória Brazil
| | - Dalton V. Vassallo
- Department of Physiological Sciences; Federal University of Espirito Santo; Vitória Brazil
- Health Science Center of Vitória-EMESCAM; Vitória Brazil
| | - Leonardo dos Santos
- Department of Physiological Sciences; Federal University of Espirito Santo; Vitória Brazil
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7
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Jiang S, Wu Y, Fang DF, Chen Y. Hypothermic preconditioning but not ketamine reduces oxygen and glucose deprivation induced neuronal injury correlated with downregulation of COX-2 expression in mouse hippocampal slices. J Pharmacol Sci 2018; 137:30-37. [PMID: 29681435 DOI: 10.1016/j.jphs.2018.04.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 03/03/2018] [Accepted: 03/29/2018] [Indexed: 01/24/2023] Open
Abstract
Hypothermic preconditioning is an effective treatment for limiting ischemic injury, but the mechanism is poorly understood. This study was aimed to explore the effect of hypothermic and ketamine preconditioning on oxygen and glucose deprivation (OGD) induced neuronal injury in mouse hippocampal slices, and to investigate its possible mechanism. The population spike (PS) was recorded in the CA1 region of mouse hippocampal slices using extracellular recordings, Na+/K+ ATPase activity in slices was determined by spectrophotometer and the expression of Cyclooxygenase-2 (COX-2) was measured by Western blot. Ten min of OGD induced a poor recovery of PS in slices after reoxygenation. Hypothermic (33 °C) preconditioning delayed the appearance of transient recovery (TR) of PS and improved the recovery amplitude of PS after reoxygenation. Hypothermic preconditioning also decreased the expression of COX-2 and increased Na+/K+ ATPase activity in slices. Pretreatment of ketamine, a non-competitive NMDA receptor antagonist at a subanesthetic dose has no effect on OGD induced neuronal injury. Moreover, the protection of hypothermic preconditioning was not added by ketamine. The downregulation of COX-2 expression and the increase of Na+/K+ ATPase activity may be associated with the effectiveness of hypothermic preconditioning in increasing tolerance to an OGD insult.
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Affiliation(s)
- Shan Jiang
- Department of Anesthesiology, The First People's Hospital of Lianyungang, Lianyungang, China; Department of Anatomy and Physiology, Lianyungang Branch of Traditional Chinese Medicine, Jiangsu Union Technical Institute, Lianyungang, China
| | - Yong Wu
- Department of Anesthesiology, The First People's Hospital of Lianyungang, Lianyungang, China
| | - De-Fang Fang
- Department of Anatomy and Physiology, Lianyungang Branch of Traditional Chinese Medicine, Jiangsu Union Technical Institute, Lianyungang, China
| | - Ying Chen
- Department of Anesthesiology, The First People's Hospital of Lianyungang, Lianyungang, China.
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Özen N, Nasırcılar Ülker S, Ülker P, Özcan F, Aslan M, Şentürk ÜK, Basralı F. Effect of 20-HETE inhibition on L-NAME-induced hypertension in rats. Clin Exp Hypertens 2017; 40:292-302. [DOI: 10.1080/10641963.2017.1368540] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Nur Özen
- Medical Faculty, Department of Physiology, Akdeniz University, Antalya, Turkey
| | | | - Pınar Ülker
- Medical Faculty, Department of Physiology, Akdeniz University, Antalya, Turkey
| | - Filiz Özcan
- Medical Faculty, Department of Biochemistry, Akdeniz University, Antalya, Turkey
| | - Mutay Aslan
- Medical Faculty, Department of Biochemistry, Akdeniz University, Antalya, Turkey
| | - Ümit Kemal Şentürk
- Medical Faculty, Department of Physiology, Akdeniz University, Antalya, Turkey
| | - Filiz Basralı
- Medical Faculty, Department of Physiology, Akdeniz University, Antalya, Turkey
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9
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Low-salt diet increases NO bioavailability and COX-2 vasoconstrictor prostanoid production in spontaneously hypertensive rats. Life Sci 2015; 145:66-73. [PMID: 26685759 DOI: 10.1016/j.lfs.2015.12.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 11/12/2015] [Accepted: 12/09/2015] [Indexed: 12/17/2022]
Abstract
AIMS The ability of dietary sodium restriction to reduce the incidence of cardiovascular mortality and improve vascular function in hypertension still remains poorly understood. The aim of this study was to observe the effects of a long period of salt restriction on the vascular reactivity of mesenteric resistance arteries of SHRs. METHODS Male SHRs received either standard-salt diet (0.3% NaCl) or low-salt diet (0.03% NaCl) for 28weeks. Vascular reactivity was studied in mesenteric artery segments and the influence of cyclooxygenase-2 (COX-2), reactive oxygen species (ROS) and participation of the renin-angiotensin system were analyzed. KEY FINDINGS Decreased salt intake did not affect phenylephrine-induced vasoconstriction but increased acetylcholine-induced vasodilatation and also increased the response to phenylephrine after inhibition of NO synthase by L-NAME (100μM) and iNOS protein expression was elevated. Cyclooxygenase inhibitor indomethacin (10μM) and COX-2 inhibitor NS 398 (1μM) decreased the reactivity to phenylephrine in low-salt-treated group, and COX-2 protein expression was elevated in low-salt group. The effects of apocynin (10μM); superoxide anion scavenger, tiron (1mM); hydrogen peroxide scavenger, catalase (1000UmL(-1)); and ACE and AT1 receptor blockers, enalapril (10μM) and losartan (10μM) on vascular reactivity were not different between two groups. The levels of AT1 protein expression were similar in both groups. SIGNIFICANCE Low-salt diet modulates mesenteric vascular responses via increased NO bioavailability suggested by increased iNOS protein expression and vasoconstrictor prostanoid production via COX-2 pathway, in SHRs. Neither ROS nor the local renin-angiotensin system is involved in these responses.
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10
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Basralı F, Koçer G, Ülker Karadamar P, Nasırcılar Ülker S, Satı L, Özen N, Özyurt D, Şentürk ÜK. Effect of magnesium supplementation on blood pressure and vascular reactivity in nitric oxide synthase inhibition-induced hypertension model. Clin Exp Hypertens 2015; 37:633-42. [DOI: 10.3109/10641963.2015.1036063] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Fontes MT, Silva TLBT, Mota MM, Barreto AS, Rossoni LV, Santos MRV. Resistance exercise acutely enhances mesenteric artery insulin-induced relaxation in healthy rats. Life Sci 2013; 94:24-9. [PMID: 24316143 DOI: 10.1016/j.lfs.2013.11.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 11/11/2013] [Accepted: 11/21/2013] [Indexed: 12/20/2022]
Abstract
AIMS We evaluated the mechanisms involved in insulin-induced vasodilatation after acute resistance exercise in healthy rats. MAIN METHODS Wistar rats were divided into 3 groups: control (CT), electrically stimulated (ES) and resistance exercise (RE). Immediately after acute RE (15 sets with 10 repetitions at 70% of maximal intensity), the animals were sacrificed and rings of mesenteric artery were mounted in an isometric system. After this, concentration-response curves to insulin were performed in control condition and in the presence of LY294002 (PI3K inhibitor), L-NAME (NOS inhibitor), L-NAME+TEA (K(+) channels inhibitor), LY294002+BQ123 (ET-A antagonist) or ouabain (Na(+)/K(+) ATPase inhibitor). KEY FINDINGS Acute RE increased insulin-induced vasorelaxation as compared to control (CT: Rmax=7.3 ± 0.4% and RE: Rmax=15.8 ± 0.8%; p<0.001). NOS inhibition reduced (p<0.001) this vasorelaxation from both groups (CT: Rmax=2.0 ± 0.3%, and RE: Rmax=-1.2 ± 0.1%), while PI3K inhibition abolished the vasorelaxation in CT (Rmax=-0.1±0.3%, p<0.001), and caused vasoconstriction in RE (Rmax=-6.5 ± 0.6%). That insulin-induced vasoconstriction on PI3K inhibition was abolished (p<0.001) by the ET-A antagonist (Rmax=2.9 ± 0.4%). Additionally, acute RE enhanced (p<0.001) the functional activity of the ouabain-sensitive Na(+)/K(+) ATPase activity (Rmax=10.7 ± 0.4%) and of the K(+) channels (Rmax=-6.1±0.5%; p<0.001) in the insulin-induced vasorelaxation as compared to CT. SIGNIFICANCE Such results suggest that acute RE promotes enhanced insulin-induced vasodilatation, which could act as a fine tuning to vascular tone.
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Affiliation(s)
- M T Fontes
- Department of Physiology, Federal University of Sergipe, 49100-000, São Cristóvão, SE, Brazil
| | - T L B T Silva
- Department of Physiology, Federal University of Sergipe, 49100-000, São Cristóvão, SE, Brazil
| | - M M Mota
- Department of Physiology, Federal University of Sergipe, 49100-000, São Cristóvão, SE, Brazil
| | - A S Barreto
- Department of Physiology, Federal University of Sergipe, 49100-000, São Cristóvão, SE, Brazil
| | - L V Rossoni
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, 05508-900, São Paulo, SP, Brazil
| | - M R V Santos
- Department of Physiology, Federal University of Sergipe, 49100-000, São Cristóvão, SE, Brazil.
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Ramos-Alves FE, de Queiroz DB, Santos-Rocha J, Duarte GP, Xavier FE. Increased cyclooxygenase-2-derived prostanoids contributes to the hyperreactivity to noradrenaline in mesenteric resistance arteries from offspring of diabetic rats. PLoS One 2012; 7:e50593. [PMID: 23209788 PMCID: PMC3509067 DOI: 10.1371/journal.pone.0050593] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 10/22/2012] [Indexed: 01/22/2023] Open
Abstract
This study analyzed the effect of in utero exposure to maternal diabetes on contraction to noradrenaline in mesenteric resistance arteries (MRA) from adult offspring, focusing on the role of cyclooxygenase (COX)-derived prostanoids. Diabetes in the maternal rat was induced by a single injection of streptozotocin (50 mg/kg body weight) on day 7 of pregnancy. Contraction to noradrenaline was analyzed in isolated MRA from offspring of diabetic (O-DR) and non-diabetic (O-CR) rats at 3, 6 and 12 months of age. Release of thromboxane A2 (TxA2) and prostaglandins E2 (PGE2) and F2α (PGF2α), was measured by specific enzyme immunoassay kits. O-DR developed hypertension from 6 months of age compared with O-CR. Arteries from O-DR were hyperactive to noradrenaline only at 6 and 12 months of age. Endothelial removal abolished this hyperreactivity to noradrenaline between O-CR and O-DR. Preincubation with either the COX-1/2 (indomethacin) or COX-2 inhibitor (NS-398) decreased noradrenaline contraction only in 6- and 12-month-old O-DR, while it remained unmodified by COX-1 inhibitor SC-560. In vessels from 6-month-old O-DR, a similar reduction in the contraction to noradrenaline produced by NS-398 was observed when TP and EP receptors were blocked (SQ29548+AH6809). In 12-month-old O-DR, this effect was only achieved when TP, EP and FP were blocked (SQ29548+AH6809+AL8810). Noradrenaline-stimulated TxB2 and PGE2 release was higher in 6- and 12-month-old O-DR, whereas PGF2α was increased only in 12-month-old O-DR. Our results demonstrated that in utero exposure to maternal hyperglycaemia in rats increases the participation of COX-2-derived prostanoids on contraction to noradrenaline, which might help to explain the greater response to this agonist in MRA from 6- and 12-month-old offspring. As increased contractile response in resistance vessels may contribute to hypertension, our results suggest a role for these COX-2-derived prostanoids in elevating vascular resistance and blood pressure in offspring of diabetic rats.
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Affiliation(s)
- Fernanda E. Ramos-Alves
- Departamento de Fisiologia e Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Pernambuco, Recife, Brazil
| | - Diego B. de Queiroz
- Departamento de Fisiologia e Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Pernambuco, Recife, Brazil
| | - Juliana Santos-Rocha
- Departamento de Fisiologia e Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Pernambuco, Recife, Brazil
| | - Gloria P. Duarte
- Departamento de Fisiologia e Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Pernambuco, Recife, Brazil
| | - Fabiano E. Xavier
- Departamento de Fisiologia e Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Pernambuco, Recife, Brazil
- * E-mail:
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Singh TU, Choudhury S, Parida S, Maruti BS, Mishra SK. Arachidonic acid inhibits Na⁺-K⁺-ATPase via cytochrome P-450, lipoxygenase and protein kinase C-dependent pathways in sheep pulmonary artery. Vascul Pharmacol 2011; 56:84-90. [PMID: 22155164 DOI: 10.1016/j.vph.2011.11.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Revised: 09/04/2011] [Accepted: 11/28/2011] [Indexed: 11/16/2022]
Abstract
The purpose of the study was to examine whether arachidonic acid inhibits vascular Na(+)-K(+)-ATPase in pulmonary vasculature and if so, what are the mechanisms involved. Functional Na(+)-K(+)-ATPase activity was studied in terms of K(+)-induced relaxation in sheep pulmonary arterial rings contracted with K(+)-free solution and 5-HT. Arachidonic acid (10-100 μM) caused concentration-dependent inhibition of KCl-induced relaxations and also increased basal arterial tone. Cytochrome P-450 inhibitor, 17-octadecynoic acid (17-ODYA) completely reversed the arachidonic acid (30 μM)-induced inhibition of KCl relaxation. Further, in the presence of HET0016, a selective blocker of 20-hydroxyeicosatetraenoic acid (20-HETE), arachidonic acid-induced inhibition of KCl relaxation was not evident. Accordingly, 20-HETE, a cytochrome P-450 metabolite of arachidonic acid, also significantly attenuated KCl-induced relaxations. Norhydihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, however, partially restored the relaxation to K(+), impaired in the presence of arachidonic acid (30 μM). On the other hand, cyclooxygenase inhibitor indomethacin failed to reverse the inhibitory effect of arachidonic acid on KCl-induced relaxation. Staurosporin, a protein kinase C inhibitor, completely reversed the inhibitory effect of arachidonic acid and 20-HETE on K(+)-induced relaxation. In conclusion, the results suggest that 20-HETE, a cytochrome P-450 metabolite of arachidonic acid has a predominant role in the inhibition of functional Na(+)-K(+)-ATPase activity in the sheep pulmonary artery, while the lipooxygenase pathway has a secondary role. It is also evident that protein kinase C is involved in the inhibition of Na(+)-K(+)-ATPase by arachidonic acid/20-HETE in sheep pulmonary artery.
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Affiliation(s)
- Thakur Uttam Singh
- Division of Pharmacology and Toxicology, Indian Veterinary Research Institute, Izatnagar-243122, Bareilly, Uttar Pradesh, India.
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Wenceslau CF, Davel AP, Xavier FE, Rossoni LV. Long-term ouabain treatment impairs vascular function in resistance arteries. J Vasc Res 2011; 48:316-26. [PMID: 21273786 DOI: 10.1159/000322576] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 10/14/2010] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND/AIMS The purpose of this study was to examine the cardiovascular effects of long-term ouabain treatment at different time points. METHODS Systolic blood pressure (SBP) was measured by tail-cuff method in male Wistar rats treated with ouabain (approx. 8.0 μg·day(-1)) or vehicle for 5, 10 and 20 weeks. Afterwards, vascular function was assessed in mesenteric resistance arteries (MRA) using a wire myograph. ROS production and COX-1 and COX-2, TNF-α, and IL-6 protein expression were investigated. RESULTS SBP was increased by ouabain treatment up to the 6th week and remained stable until the 20th week. However, noradrenaline-induced contraction increased only in MRA in rats treated with ouabain for 20 weeks. NOS inhibition and endothelium removal increased the noradrenaline response, but to a smaller magnitude in MRA in the ouabain group. Moreover, inhibition of COX-2 or incubation with superoxide dismutase restores noradrenaline-induced contraction in the 20-week ouabain group to control levels. ROS production as well as COX-2, IL-6 and TNF-α protein expression increased in MRA in this group. CONCLUSION Although ouabain treatment induced hypertension in all groups, a larger noradrenaline induced contraction was observed over 20 weeks of treatment. This vascular dysfunction was related to COX-2-derived prostanoids and oxidative stress, increased pro- inflammatory cytokines and reduced NO bioavailability.
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Affiliation(s)
- Camilla Ferreira Wenceslau
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
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15
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Time-dependent increases in ouabain-sensitive Na+, K+-ATPase activity in aortas from diabetic rats: The role of prostanoids and protein kinase C. Life Sci 2010; 87:302-8. [DOI: 10.1016/j.lfs.2010.07.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 06/24/2010] [Accepted: 07/01/2010] [Indexed: 11/21/2022]
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16
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Vlkovicová J, Javorková V, Mézesová L, Pechánová O, Andriantsitohaina R, Vrbjar N. Dual effect of polyphenolic compounds on cardiac Na+/K+-ATPase during development and persistence of hypertension in rats. Can J Physiol Pharmacol 2009; 87:1046-54. [PMID: 20029541 DOI: 10.1139/y09-099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The enzyme kinetics of cardiac Na(+)/K(+)-ATPase were used for characterizing the ATP- and Na(+)-binding sites after administration of red wine polyphenolic compounds (Provinol) during developing and sustained hypertension. Hypertension was induced in rats (LN group) by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 40 mg*kg(-1)*day(-1)). Provinol (40 mg*kg(-1)*day(-1)) was applied during developing hypertension (LNPF4 group) and sustained hypertension (LNPF7/3 group). Provinol reduced the number of active Na(+)/K(+)-ATPase molecules in cardiac tissue, as indicated by decreased V(max) values (by 33% in LNPF4 and 26% in LNPF7/3 compared with LN). Concerning qualitative properties of the enzyme, Provinol induced different effects on the ATP- and Na(+)-binding sites of Na(+)/K(+)-ATPase. The ATP-binding site was impaired by Provinol, as indicated by increased K(m) value (by 52% in LNPF4 vs. LN), suggesting worsened utilization of substrate by the enzyme. In sustained hypertension, however, Provinol had no effect on the ATP-binding site, as indicated by unchanged K(m) value (LNPF7/3 vs. LN). On the other hand, the Na(+)-binding site was protected by Provinol, as suggested by decreased K(Na) value (by 72% in LNPF4 and 69% in LNPF7/3 vs. LN), indicating an increased affinity of the enzyme for sodium. Thus, Provinol appeared to stimulate the extrusion of Na(+) from cardiac cells, especially in the physiologically important range of sodium concentrations (2-10 mmol*L(-1)), during both developing and sustained hypertension.
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Affiliation(s)
- Jana Vlkovicová
- Institute for Heart Research, Department of Biochemistry, Slovak Academy of Sciences, Bratislava, Slovak Republic
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17
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Kuru O, Sentürk UK, Koçer G, Ozdem S, Başkurt OK, Cetin A, Yeşilkaya A, Gündüz F. Effect of exercise training on resistance arteries in rats with chronic NOS inhibition. J Appl Physiol (1985) 2009; 107:896-902. [PMID: 19498093 DOI: 10.1152/japplphysiol.91180.2008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Regular exercise has blood pressure-lowering effects, as shown in different types of experimental hypertension models in rats, including the nitric oxide synthase (NOS) inhibition model. We aimed to investigate possible mechanisms implicated in the exercise effect by evaluating the vasoreactivity of resistance arteries. Exercise effects on agonist-induced vasodilatory responses and flow-mediated dilation were evaluated in vessel segments of the rat chronic NOS inhibition model. Normotensive and hypertensive rats were subjected to swimming exercise (1 h/day, 5 days/wk, 6 wk), while rats in other sedentary and hypertensive groups did not. Hypertension was induced by oral administration of the nonselective NOS inhibitor l-NAME (25 mg/kg day) for 6 wk. Systolic blood pressure, as measured by the tail-cuff method, was significantly decreased by the training protocol in exercising hypertensive rats. The vasoreactivity of resistance arteries was evaluated by both wire and pressure myography studies. An impaired nitric oxide-mediated relaxation pathway in untrained hypertensive rats led to decreased relaxation responses in vessels with intact endothelium. Exercise training significantly improved the responses to acetylcholine and flow-mediated dilation in exercise-trained hypertensive rats in parallel with a decrease in blood pressure. On the other hand contraction (norepinephrine and KCl) and relaxation (sodium nitroprusside) responses of vascular smooth muscle were not different between the groups. Vascular endothelial NOS protein expression was found to be increased in both exercising groups. In conclusion, these results revealed evidence of an increased role of the nitric oxide-dependent relaxation pathway in exercising hypertensive rats.
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Affiliation(s)
- Oktay Kuru
- School of Health Sciences, Mugla University, Mugla, Turkey
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18
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Chronic ouabain treatment exacerbates blood pressure elevation in spontaneously hypertensive rats: the role of vascular mechanisms. J Hypertens 2009; 27:1233-42. [DOI: 10.1097/hjh.0b013e32832a391f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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19
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Afkir S, Nguelefack TB, Aziz M, Zoheir J, Cuisinaud G, Bnouham M, Mekhfi H, Legssyer A, Lahlou S, Ziyyat A. Arbutus unedo prevents cardiovascular and morphological alterations in L-NAME-induced hypertensive rats Part I: cardiovascular and renal hemodynamic effects of Arbutus unedo in L-NAME-induced hypertensive rats. JOURNAL OF ETHNOPHARMACOLOGY 2008; 116:288-295. [PMID: 18191352 DOI: 10.1016/j.jep.2007.11.029] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 11/14/2007] [Accepted: 11/20/2007] [Indexed: 05/25/2023]
Abstract
Hypertension induced by nitric oxide synthase inhibition is associated with functional abnormalities of the heart and kidney. The aim of the present study was to investigate whether chronic treatment with Arbutus unedo leaf (AuL) or root (AuR) aqueous extracts can prevent these alterations. Six groups of rats were used: control group received tap water; N(G)-nitro-l-arginine methyl-ester (L-NAME) group treated with L-NAME at 40 mg/kg/day; AuL and AuR groups received simultaneously L-NAME (40 mg/kg/day) and Au leaves or roots extract at the same concentration 250 mg/kg/day; l-arginine and enalapril groups received simultaneously L-NAME (40 mg/kg/day) and l-arginine at 50mg/kg/day or enalapril at 15 mg/kg/day. Treatment of rats during 4 weeks with L-NAME caused an increase of the systolic blood pressure (SBP) accompanied by a ventricular hypertrophy, an impairment of endothelium-dependent vasorelaxation, an increase of the cardiac baroreflex sensitivity and a decrease of water, sodium and potassium excretion. The co-administration of AuL or AuR extracts with L-NAME reduces the development of increased SBP, ameliorates the vascular reactivity as well as the baroreflex sensitivity and normalizes the renal function. AuR reduces the ventricular hypertrophy but AuL do not. Enalapril associated with L-NAME reverses the majority of alterations induced by L-NAME while l-arginine only lightly ameliorates the vascular reactivity. These results show that chronic treatment with Arbutus extract regress the development of hypertension and ameliorate cardiovascular and renal functions in NO deficient hypertension.
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Affiliation(s)
- Saida Afkir
- UFR Physiologie et Pharmacologie, Laboratoire de Physiologie et Ethnopharmacologie, Département de Biologie, Faculté des Sciences, Université Mohamed Premier, BP 717, Bd Mohamed VI, 60000 Oujda, Morocco
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20
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Javorková V, Vlkovicova J, Kunes J, Pechanova O, Zicha J, Vrbjar N. Effect of maturation on renal Na+/K+-atpase and its susceptibility to nitric oxide-deficient hypertension in rats. Clin Exp Pharmacol Physiol 2007; 34:617-23. [PMID: 17581218 DOI: 10.1111/j.1440-1681.2007.04629.x] [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: 11/30/2022]
Abstract
1. The present study deals with the effect of maturation on the kinetic properties of renal Na(+)/K(+)-ATPase and its susceptibility to nitric oxide (NO)-deficient hypertension induced by the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). 2. Immature (4-week-old) and adult (12-week-old) male Wistar rats were administered L-NAME (40 mg/kg per day) in their drinking water for 4 weeks. 3. The properties of the ATP- and Na(+)-binding sites of Na(+)/K(+)-ATPase were investigated by activation of the enzyme with increasing concentrations of the energy substrate ATP and/or cofactor Na(+). Unchanged values of K(m) suggest that energy utilization by the enzyme in the kidney of control rats remains unaffected during maturation. Conversely, the decrease in K(Na) values (the concentration of Na(+) necessary to achieve half-maximal reaction velocity) indicates improved affinity for Na(+) in the older group of control rats. 4. Application of L-NAME to all young animals had no significant effect on the functional properties of Na(+)/K(+)-ATPase. 5. In adult animals, the V(max) values remained unchanged after treatment with L-NAME, but the affinities of the ATP- and Na(+)-binding sites were decreased, as indicated by significant increase in K(m) and K(Na) values. 6. Maturation of control rats was accompanied by an increase in the Na(+) affinity of renal Na(+)/K(+)-ATPase without affecting ATP utilization. However, maturation increased the susceptibility of renal Na(+)/K(+)-ATPase to the harmful effects of L-NAME.
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Affiliation(s)
- Veronika Javorková
- Institute for Heart Research, Department of Biochemistry, Slovak Academy of Sciences, Bratislava, Slovak Republic
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21
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dos Santos L, Gonçalves MV, Vassallo DV, Oliveira EM, Rossoni LV. Effects of high sodium intake diet on the vascular reactivity to phenylephrine on rat isolated caudal and renal vascular beds: Endothelial modulation. Life Sci 2005; 78:2272-9. [PMID: 16289140 DOI: 10.1016/j.lfs.2005.09.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Accepted: 09/15/2005] [Indexed: 10/25/2022]
Abstract
High salt intake is involved in the genesis of hypertension and vascular changes in salt-sensitive patients. Although many mechanisms have been proposed, the underlying mechanisms of these alterations in healthy rats are not completely elucidated. The aim of this study was to investigate if male Wistar rats fed a high salt diet, NaCl 1.8% in drinking water for 4 weeks, develop changes in the pressor reactivity of isolated tail and renal vascular beds. Salt treatment increased mean arterial pressure (SALT = 124 +/- 2.2 vs. CT = 111 +/- 3.9 mmHg; p < 0.01) and urinary sodium excretion in the absence of changes in sodium plasma levels. Pressor reactivity was generated in isolated tail and kidney vascular beds as dose-response curves to phenylephrine (PHE = 0.01 to 300 microg). SALT increased the reactivity (E(max): SALT = 378 +/- 15.8 vs. CT = 282 +/- 10 mmHg; p < 0.01) without changing the sensitivity (pD(2)) to PHE in the tail vascular bed. However, these parameters did not change in the renal bed. In subsequent studies on the isolated caudal vascular bed, we found that endothelial damage, but not L-NAME (100 microM) or indomethacin (10 microM), abolished the increment in E(max) to PHE induced by SALT. On the other hand, losartan (100 microM) reduced E(max) in SALT to CT values. Additionally, local angiotensin-converting enzyme activity in segments from tail artery increased by 95%. In conclusion, 4 weeks of high salt diet increases blood pressure and induces specific territorial vascular changes in response to PHE. Results also suggest that the increment in E(max) in the tail vascular bed from SALT rats was endothelium-dependent and was mediated by the activation of the local renin-angiotensin system.
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Affiliation(s)
- Leonardo dos Santos
- Departamento de Ciências Fisiológicas, Centro Biomédico, Universidade Federal do Espírito Santo, Brazil
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22
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Preti SC, da Cunha V, Vassallo DV, Stefanon I. The Superoxide Dismutase Mimetic, Tempol, Reduces the Bioavailability of Nitric Oxide and does not Alter L-NAME-Induced Hypertension in Rats. Basic Clin Pharmacol Toxicol 2005; 97:29-34. [PMID: 15943756 DOI: 10.1111/j.1742-7843.2005.pto_97105.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
L-NAME-induced hypertension is characterized by chronic inhibition of nitric oxide synthesis. We have investigated if tempol, an agent mimicking superoxide dismutase might reduce hypertension and the increased vascular reactivity to pressor agents. Rats were divided into: Control, animals receiving L-NAME 50 mg kg(-1)day(-1), tempol 200 mg kg(-1)day(-1) and tempol plus L-NAME. Drugs were administrated in the drinking water for seven days. L-NAME increased mean arterial blood pressure (Control: 108+/-3 mmHg versus L-NAME 181+/-5 mmHg; P<0.05). Tempol did not change arterial pressure and heart rate in L-NAME and Control groups. The reactivity to phenylephrine increased in the L-NAME group (E(max) Control: 2.00+/-0.15 g versus L-NAME: 2.45+/-0.14 g); tempol+L-NAME (E(max): 2.55+/-0.15 g) and in the tempol group (E(max): 2.57+/-0.14 g). Maximal relaxation induced by acetylcholine was reduced in L-NAME group (60.9+/-3%) and tempol+L-NAME (37.4+/-6%) compared to Control (99.1+/-0.12%) and tempol groups (95.6+/-2.12%). All treated groups presented a reduction in the effects of L-NAME administration on basal vascular tone. Our results show that tempol, in the dose used in this study, did not change the effects of L-NAME on blood pressure which suggests that tempol reduces bioavailability of nitric oxide on aortic isolated ring.
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Affiliation(s)
- Silvio César Preti
- Department of Physiological Sciences, Federal University of Espirito Santo, Vitoria, ES, Brazil
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23
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Armitage JA, Lakasing L, Taylor PD, Balachandran AA, Jensen RI, Dekou V, Ashton N, Nyengaard JR, Poston L. Developmental programming of aortic and renal structure in offspring of rats fed fat-rich diets in pregnancy. J Physiol 2005; 565:171-84. [PMID: 15774514 PMCID: PMC1464506 DOI: 10.1113/jphysiol.2005.084947] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Evidence from human and animal studies suggests that maternal nutrition can induce developmental programming of adult hypertension in offspring. We have previously described a model of maternal dietary imbalance in Sprague-Dawley rats whereby administration of a maternal diet rich in animal lard programmes the development of increased blood pressure, insulin resistance, dyslipidaemia, obesity and mesenteric artery endothelial dysfunction in adult offspring. To further characterize the mechanism of hypertension in this model we have examined vascular and renal structure in adult offspring of Sprague-Dawley rats fed a control diet (OC) or lard-rich diet (OHF) during pregnancy and suckling followed by a control diet post-weaning. To gain further insight, we assessed aortic reactivity and elasticity in an organ bath preparation and renal renin and Na+,K+-ATPase activity. Plasma aldosterone concentration was also measured. Stereological examination of the aorta in OHF demonstrated reduced endothelial cell volume and smooth muscle cell number compared with OC. Adult OHF animals showed increased aortic stiffness and reduced endothelium-dependent relaxation. Renal stereology showed no differences in kidney weight, glomerular number or volume in OHF compared with OC, but renin and Na+,K+-ATPase activity were significantly reduced in OHF compared with controls. Programmed alterations to aortic structure and function are consistent with previous observations that exposure to maternal high fat diets produces systemic vascular changes in the offspring. Despite normal renal stereology, altered renal Na+,K+-ATPase and renin activity offers further insight into the mechanism underlying the increased blood pressure characteristic of this model.
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Affiliation(s)
- James A Armitage
- Maternal and Fetal Research Unit, Division of Reproductive Health, Endocrinology and Development, King's College London, GKT Department of Women's Health, St Thomas' Hospital, UK.
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Vlkovicová J, Javorková V, Pechánová O, Vrbjar N. Gender difference in functional properties of Na,K-ATPase in the heart of spontaneously hypertensive rats. Life Sci 2005; 76:971-82. [PMID: 15607327 DOI: 10.1016/j.lfs.2004.10.013] [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: 05/19/2004] [Accepted: 06/17/2004] [Indexed: 10/26/2022]
Abstract
The aim of present study was the investigation of functional properties of the cardiac Na,K-ATPase in 16 weeks old male and female spontaneously hypertensive rats (SHR). The Na,K-ATPase activity in the presence of increasing concentrations of ATP, as well as Na(+) was lower in SHR of both genders, as compared to respective normotensive controls. Evaluation of kinetic parameters revealed a significant decrease of the maximum velocity (V(max)) in males (30% for ATP-activation, 40% for Na(+)-activation), as well as in females (24% for ATP, 29% for Na(+)), indicating a hypertension-induced diminution of the number of active enzyme molecules in cardiac sarcolemma. Insignificant changes were observed in the value of Michaelis-Menten constant (K(m)) in both cases. The concentration of sodium that gives half-maximal reaction velocity (K(Na)), increased by 38% in male and by 70% in female SHR. This impairment in the affinity of the Na(+)-binding site together with decreased number of active Na,K-ATPase molecules are probably responsible for the deteriorated enzyme-function in hearts of SHR. Direct comparison of SHR of both genders showed, that the enzyme from female hearts seems to be adapted better to hypertension as documented by its increased activity as a consequence of improved ability to bind and utilize ATP, as suggested by 32% decrease of K(m) value in females. In addition, the enzyme from female hearts is able to increase its activity (by 41%) in the presence of increasing sodium concentration even in the range where the enzyme from male hearts is already saturated.
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Affiliation(s)
- Jana Vlkovicová
- Institute for Heart Research, Department of Biochemistry, Slovak Academy of Sciences, Dúbravská cesta 9, P.O. Box 104, 840 05 Bratislava 45, Slovak Republic
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