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1.
Braz. j. med. biol. res ; 53(3): e8761, 2020. tab, graf
Article in English | LILACS | ID: biblio-1089339

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.


Subject(s)
Animals , Male , Physical Conditioning, Animal/physiology , Calcium/analysis , Nitric Oxide Synthase/drug effects , NG-Nitroarginine Methyl Ester/pharmacology , Enzyme Inhibitors/pharmacology , Myocardial Contraction/drug effects , Body Weight/physiology , Rats, Wistar , Ventricular Pressure/drug effects , Nitric Oxide Synthase/metabolism , NG-Nitroarginine Methyl Ester/administration & dosage , Models, Animal , Myocytes, Cardiac/drug effects , Myocytes, Cardiac/physiology , Enzyme Inhibitors/administration & dosage , Adiposity , Hemodynamics , Motor Activity/physiology , Myocardium/pathology
2.
Medisan ; 23(2)mar.-abr. 2019. ilus
Article in Spanish | LILACS | ID: biblio-1002636

ABSTRACT

Los digitálicos son fármacos con capacidad de aumentar la contractilidad miocárdica (inotrópico positivo), que han desempeñado un rol primordial en el tratamiento de pacientes con insuficiencia cardiaca; su uso inapropiado puede traer complicaciones serias a estos pacientes, incluso, hasta la muerte. La más importante de estas complicaciones es la intoxicación digitálica, originada por la sobredosis de dichos fármacos, a causa de la combinación del efecto inhibitorio en la conducción nodal y la estimulación sobre las fibras individuales auriculares y ventriculares. Debido al uso frecuente de estos medicamentos en todos los niveles de atención de salud y lo difícil que resulta diagnosticar dicha complicación por la complejidad de su cuadro clínico y de su expresión electrocardiográfica, se realizó una revisión bibliográfica exhaustiva sobre el tema para brindar amplia información, que permita una atención adecuada a los pacientes con este diagnóstico


Digitalis are drugs with the capacity of increasing myocardial contractility (inotropic positive agents) which have carried out an important role in the treatment of heart failure; their inappropriate use can bring severe complications to the patient, even, to death. The most important in these complications is the digitalis toxicity, originated by the overdose of these drugs, caused by the combination of the inhibitory effect in the nodal conduction and stimulation on the individual atrial and ventricular fibers. Due to the frequent use of these medications at all levels of medical care and to the difficulty in diagnosing this complication caused by the complexity of their clinical pattern and of their electrocardiographic expression, an exhaustive literature review was carried out on the topic to give a wide information that allows an appropriate care to the patients with this diagnosis


Subject(s)
Humans , Male , Female , Digitalis Glycosides/poisoning , Digitalis Glycosides/pharmacology , Drug-Related Side Effects and Adverse Reactions , Myocardial Contraction/drug effects , Poisoning , Drug Overdose/metabolism
3.
Arq. bras. cardiol ; 105(3): 235-240, Sept. 2015. tab, ilus
Article in English | LILACS | ID: lil-761504

ABSTRACT

AbstractBackground:One of the most important thyroid hormone targets is the cardiovascular system. Hemodynamic changes, such as decreased resting heart rate (HR), myocardial contractility, and cardiac output, and increased diastolic pressure and systemic vascular resistance, have been observed in hypothyroid patients. Moreover, in these patients, ECG changes include sinus bradycardia and low voltage complexes (P waves or QRS complexes).Objective:This study aimed at evaluating the prophylactic effect of apelin on HR changes and QRS voltage that occur in propylthiouracil (PTU)-induced hypothyroid rats.Method:In this study, 48 adult male Wistar rats weighing 170-235g were randomly divided into 6 groups: Control group (normal saline ip injection + tap water gavage); P group (PTU 0.05%, in drinking water); A group (apelin 200 µg.kg-1.day-1, ip); PA group [co-administration of PTU and apelin]; PT group [co-administration of PTU + T4 (0.2 mg/g per day, gavage)]; and PAT group (co-administration of PTU, apelin and T4). All experiments were performed for 28 consecutive days, and then the animals were anesthetized with an ip injection of ketamine (80 mg/kg) and xylazine (12 mg/kg). Lead II electrocardiogram was recorded to calculate HR and QRS voltage.Results:Heart rate and QRS voltage increased more significantly in the hypothyroid group that consumed both apelin and T4 (201 ± 4 beat/min, 0.71 ± 0.02 mv vs. hypothyroid 145 ± 9 beat/min, 0.563 ± 0.015 mv; respectively).Conclusion:The co-administration of apelin and T4 showed a protective effect on QRS voltage and HR in PTU‑induced hypothyroid rats.


ResumoFundamento:O sistema cardiovascular é um dos alvos mais importantes dos hormônios tireoidianos. As seguintes alterações hemodinâmicas foram observadas em pacientes com hipotireoidismo: redução da frequência cardíaca (FC) de repouso, da contratilidade miocárdica e do débito cardíaco; e aumento da pressão diastólica e da resistência vascular sistêmica. Além disso, tais pacientes apresentam alterações eletrocardiográficas, como bradicardia sinusal e baixa voltagem dos complexos (ondas P e complexos QRS).Objetivo:Avaliar o efeito profilático da apelina nas alterações de FC e voltagem de QRS que ocorrem em ratos com hipotireoidismo induzido por propiltiouracil (PTU).Método:Este estudo dividiu de maneira aleatória 48 ratos Wistar machos adultos, pesando 170-235g, em seis grupos: grupo controle (CO), injeção intraperitoneal (ip) de solução salina + água potável gavagem; grupo hipotireoideo (P), PTU 0,05% em água potável; grupo A, apelina ip (200 µg.kg-1.dia-1); grupo PA, coadministração de PTU e apelina; grupo PT, coadministração de PTU e T4, 0.2 mg/g por dia por gavagem; e grupo PAT, coadministração de PTU, apelina e T4. Todos os experimentos foram realizados durante 28 dias consecutivos, sendo então os animais anestesiados com injeção ip de cetamina (80 mg/kg) e xilazina (12 mg/kg). Utilizou-se o registro do ECG na derivação DII para calcular a FC e a voltagem do QRS.Resultados:Houve aumento mais significativo da FC e da voltagem do QRS no grupo hipotireoideo que recebeu apelina e T4 (201±4 bpm, 0,71±0,02mV) do que no hipotireoideo (145±9 bpm, 0,563±0,015 mV), respectivamente.Conclusão:A coadministração de apelina e T4 mostrou efeito protetor na voltagem do QRS e FC em ratos com hipotireoidismo induzido por PTU.


Subject(s)
Animals , Male , Cardiotonic Agents/administration & dosage , Heart Rate/drug effects , Hypothyroidism/physiopathology , Intercellular Signaling Peptides and Proteins/administration & dosage , Myocardial Contraction/drug effects , Thyroxine/administration & dosage , Antithyroid Agents , Body Weight , Drug Combinations , Electrocardiography , Hypothyroidism/chemically induced , Propylthiouracil , Random Allocation , Rats, Wistar , Reproducibility of Results , Thyrotropin/blood , Thyroxine/blood
4.
Acta cir. bras ; 30(7): 484-490, 07/2015. graf
Article in English | LILACS | ID: lil-754985

ABSTRACT

PURPOSE: To study racemic bupivacaine, non-racemic bupivacaine and ropivacaine on myocardial contractility. METHODS: Isolated Wistar papillary muscles were submitted to 50 and 100 mM racemic bupivacaine (B50 and B100), non-racemic bupivacaine (NR50 and NR100) and ropivacaine (R50 and R100) intoxication. Isometric contraction data were obtained in basal condition (0.2 Hz), after increasing the frequency of stimulation to 1.0 Hz and after 5, 10 and 15 min of local anesthetic intoxication. Data were analyzed as relative changes of variation. RESULTS: Developed tension was higher with R100 than B100 at D1 (4.3 ± 41.1 vs -57.9 ± 48.1). Resting tension was altered with B50 (-10.6 ± 23.8 vs -4.7 ± 5.0) and R50 (-14.0 ± 20.5 vs -0.5 ± 7.1) between D1 and D3. Maximum rate of tension development was lower with B100 (-56.6 ± 38.0) than R50 (-6.3 ± 37.9) and R100 (-1.9 ± 37.2) in D1. B50, B100 and NR100 modified the maximum rate of tension decline from D1 through D2. Time to peak tension was changed with NR50 between D1 and D2. CONCLUSIONS: Racemic bupivacaine depressed myocardial contractile force more than non-racemic bupivacaine and ropivacaine. Non-racemic and racemic bupivacaine caused myocardial relaxation impairment more than ropivacaine. .


Subject(s)
Animals , Male , Amides/pharmacology , Anesthetics, Local/pharmacology , Bupivacaine/pharmacology , Myocardial Contraction/drug effects , Bupivacaine/chemistry , Depression, Chemical , Muscle Tonus/drug effects , Muscle Tonus/physiology , Myocardial Contraction/physiology , Papillary Muscles/drug effects , Papillary Muscles/physiology , Rats, Wistar , Reference Values , Stereoisomerism , Time Factors
6.
Braz. j. med. biol. res ; 47(4): 328-333, 8/4/2014. graf
Article in English | LILACS | ID: lil-705768

ABSTRACT

In cardiac and skeletal muscle, eugenol (μM range) blocks excitation-contraction coupling. In skeletal muscle, however, larger doses of eugenol (mM range) induce calcium release from the sarcoplasmic reticulum. The effects of eugenol are therefore dependent on its concentration. In this study, we evaluated the effects of eugenol on the contractility of isolated, quiescent atrial trabeculae from male Wistar rats (250-300 g; n=131) and measured atrial ATP content. Eugenol (1, 3, 5, 7, and 10 mM) increased resting tension in a dose-dependent manner. Ryanodine [100 µM; a specific ryanodine receptor (RyR) blocker] and procaine (30 mM; a nonspecific RyR blocker) did not block the increased resting tension induced by eugenol regardless of whether extracellular calcium was present. The myosin-specific inhibitor 2,3-butanedione monoxime (BDM), however, reversed the increase in resting tension induced by eugenol. In Triton-skinned atrial trabeculae, in which all membranes were solubilized, eugenol did not change resting tension, maximum force produced, or the force vs pCa relationship (pCa=-log [Ca2+]). Given that eugenol reduced ATP concentration, the increase in resting tension observed in this study may have resulted from cooperative activation of cardiac thin filaments by strongly attached cross-bridges (rigor state).


Subject(s)
Animals , Male , Calcium/physiology , Eugenol/pharmacology , Excitation Contraction Coupling/drug effects , Heart Atria/drug effects , Muscle Strength/drug effects , Myocardial Contraction/drug effects , Adenosine Triphosphate/analysis , Anesthetics, Local/pharmacology , Eugenol/administration & dosage , In Vitro Techniques , Luciferases , Muscle, Skeletal/drug effects , Procaine/pharmacology , Rats, Wistar , Ryanodine/pharmacology
7.
Braz. j. med. biol. res ; 46(2): 178-185, 01/fev. 2013. tab, graf
Article in English | LILACS | ID: lil-668775

ABSTRACT

We studied the effects of the acute administration of small doses of lead over time on hemodynamic parameters in anesthetized rats to determine if myocardial contractility changes are dependent or not on the development of hypertension. Male Wistar rats received 320 µg/kg lead acetate iv once, and their hemodynamic parameters were measured for 2 h. Cardiac contractility was evaluated in vitro using left ventricular papillary muscles as were Na+,K+-ATPase and myosin Ca2+-ATPase activities. Lead increased left- (control: 112 ± 3.7 vs lead: 129 ± 3.2 mmHg) and right-ventricular systolic pressures (control: 28 ± 1.2 vs lead: 34 ± 1.2 mmHg) significantly without modifying heart rate. Papillary muscles were exposed to 8 µM lead acetate and evaluated 60 min later. Isometric contractions increased (control: 0.546 ± 0.07 vs lead: 0.608 ± 0.06 g/mg) and time to peak tension decreased (control: 268 ± 13 vs lead: 227 ± 5.58 ms), but relaxation time was unchanged. Post-pause potentiation was similar between groups (n = 6 per group), suggesting no change in sarcoplasmic reticulum activity, evaluated indirectly by this protocol. After 1-h exposure to lead acetate, the papillary muscles became hyperactive in response to a β-adrenergic agonist (10 µM isoproterenol). In addition, post-rest contractions decreased, suggesting a reduction in sarcolemmal calcium influx. The heart samples treated with 8 µM lead acetate presented increased Na+,K+-ATPase (approximately 140%, P < 0.05 for control vs lead) and myosin ATPase (approximately 30%, P < 0.05 for control vs lead) activity. Our results indicated that acute exposure to low lead concentrations produces direct positive inotropic and lusitropic effects on myocardial contractility and increases the right and left ventricular systolic pressure, thus potentially contributing to the early development of hypertension.


Subject(s)
Animals , Male , Hypertension/physiopathology , Myocardial Contraction/drug effects , Myosins/drug effects , Organometallic Compounds/pharmacology , Adenosine Triphosphatases/drug effects , Enzyme Activation , Hypertension/enzymology , Myocardial Contraction/physiology , Myosins/physiology , Rats, Wistar
8.
Arch. cardiol. Méx ; 82(4): 320-323, oct.-dic. 2012.
Article in Spanish | LILACS | ID: lil-695069

ABSTRACT

En este artículo se presenta una idea original: inhibir la contracción miocárdica en forma regional y selectiva sin inducir necrosis. Se propone como una posible opción terapéutica en miocardiopatía hipertrófica asimétrica obstructiva, y se plantean 2 modelos farmacológicos basados en la administración intramiocárdica de toxina botulínica y de wortmanina.


The purpose of this paper is to introduce a new idea: local inhibition of contractility without necrosis. It's potential usefulness in hypertrophic cardiomyopathy treatment is discussed and 2 pharmacological models, administrating botulinum toxin and wortmannin directly in the myocardium are disclosed.


Subject(s)
Androstadienes/administration & dosage , Botulinum Toxins/administration & dosage , Cardiomyopathy, Hypertrophic/drug therapy , Models, Theoretical , Androstadienes/pharmacology , Botulinum Toxins/pharmacology , Injections, Intralesional , Myocardial Contraction/drug effects , Necrosis/prevention & control
9.
Ann Card Anaesth ; 2012 Apr; 15(2): 128-133
Article in English | IMSEAR | ID: sea-139654

ABSTRACT

We aimed to investigate whether low-dose vasopressin administered to patients undergoing coronary artery bypass grafting (CABG) surgery with preexisting mild to moderate systolic dysfunction can produce sustained improvement in cardiac function. This double-blind randomized study was conducted in a hospital where a single anesthetic and surgical team performed elective CABG. Twenty patients aged 32-61 years who underwent elective CABG between January 2007 and December 2007 were enrolled in this study. The patients randomly received either vasopressin 0.03 IU/min (Group A) or normal saline (Group B) in equal volume for 60 min after cardiopulmonary bypass (CPB). The cardiac output, cardiac index, stroke volume index, fractional area of contraction and systemic vascular resistance index were significantly higher in Group A than in Group B. Adrenaline (mean dose: 0.06 μg/kg•min-1) was required in seven patients from Group B but in none of the Group A patients on initial separation from CPB (P< 0.05). Of the 10 patients in Group B, five required phenylepherine to maintain the mean arterial pressure (MAP) >65 mmHg, whereas none of the Group A patients required phenylephrine for MAP regulation (P< 0.05). We conclude that Infusion of low-dose vasopressin for patients with mild to moderate left ventricular systolic dysfunction during separation from CPB is beneficial for the postoperative hemodynamic profile, reduces the catecholamine doses required and improves left ventricular systolic function.


Subject(s)
Adult , Anesthesia , Blood Pressure/drug effects , Cardiac Catheterization , Cardiac Output/drug effects , Cardiopulmonary Bypass/methods , Double-Blind Method , Echocardiography, Transesophageal , Female , Hemostatics/administration & dosage , Hemostatics/therapeutic use , Humans , Male , Middle Aged , Myocardial Contraction/drug effects , Phenylephrine/therapeutic use , Stroke Volume/drug effects , Vascular Resistance/drug effects , Vasoconstrictor Agents/therapeutic use , Vasopressins/administration & dosage , Vasopressins/therapeutic use , Ventricular Function, Left/drug effects
10.
Arq. bras. cardiol ; 98(3): 243-251, mar. 2012. tab
Article in Portuguese | LILACS | ID: lil-622515

ABSTRACT

FUNDAMENTO: A Contração Pós-Repouso (CPR) do músculo cardíaco fornece informações indiretas sobre a manipulação de cálcio intracelular. OBJETIVO: Nosso objetivo foi estudar o comportamento da CPR e seus mecanismos subjacentes em camundongos com infarto do miocárdio. MÉTODOS: Seis semanas após a oclusão coronariana, a contratilidade dos Músculos Papilares (MP) obtidos a partir de camundongos submetidos à cirurgia sham (C, n = 17), com infarto moderado (MMI, n = 10) e grande infarto (LMI, n = 14), foi avaliada após intervalos de repouso de 10 a 60 segundos antes e depois da incubação com cloreto de lítio (Li+) em substituição ao cloreto de sódio ou rianodina (Ry). A expressão proteica de SR Ca(2+)-ATPase (SERCA2), trocador Na+/Ca2+ (NCX), fosfolambam (PLB) e fosfo-Ser (16)-PLB foi analisada por Western blotting. RESULTADOS: Os camundongos MMI apresentaram potenciação de CPR reduzida em comparação aos camundongos C. Em oposição à potenciação normal para camundongos C, foram observadas degradações de força pós-repouso nos músculos de camundongos LMI. Além disso, a Ry bloqueou a degradação ou potenciação de PRC observada em camundongos LMI e C; o Li+ inibiu o NCX e converteu a degradação em potenciação de CPR em camundongos LMI. Embora os camundongos MMI e LMI tenham apresentado diminuição no SERCA2 (72 ± 7% e 47 ± 9% de camundongos controle, respectivamente) e expressão protéica de fosfo-Ser16-PLB (75 ± 5% e 46 ± 11%, respectivamente), a superexpressão do NCX (175 ± 20%) só foi observada nos músculos de camundongos LMI. CONCLUSÃO: Nossos resultados mostraram, pela primeira vez, que a remodelação miocárdica pós-IAM em camundongos pode mudar a potenciação regular para degradação pós-repouso, afetando as proteínas de manipulação de Ca(2+) em miócitos.


BACKGROUND: Post-rest contraction (PRC) of cardiac muscle provides indirect information about the intracellular calcium handling. OBJECTIVE: Our aim was to study the behavior of PRC, and its underlying mechanisms, in rats with myocardial infarction. METHODS: Six weeks after coronary occlusion, the contractility of papillary muscles (PM) obtained from sham-operated (C, n=17), moderate infarcted (MMI, n=10) and large infarcted (LMI, n=14) rats was evaluated, following rest intervals of 10 to 60 seconds before and after incubation with lithium chloride (Li+) substituting sodium chloride or ryanodine (Ry). Protein expression of SR Ca(2+)-ATPase (SERCA2), Na+/Ca2+ exchanger (NCX), phospholamban (PLB) and phospho-Ser(16)-PLB were analyzed by Western blotting. RESULTS: MMI exhibited reduced PRC potentiation when compared to C. Opposing the normal potentiation for C, post-rest decays of force were observed in LMI muscles. In addition, Ry blocked PRC decay or potentiation observed in LMI and C; Li+ inhibited NCX and converted PRC decay to potentiation in LMI. Although MMI and LMI presented decreased SERCA2 (72±7% and 47±9% of Control, respectively) and phospho-Ser16-PLB (75±5% and 46±11%, respectively) protein expression, overexpression of NCX (175±20%) was only observed in LMI muscles. CONCLUSION: Our results showed, for the first time ever, that myocardial remodeling after MI in rats may change the regular potentiation to post-rest decay by affecting myocyte Ca(2+) handling proteins.


FUNDAMENTO: La Contracción pos pausa (CPP) del músculo cardíaco provee informaciones indirectas sobre la manejo del calcio intracelular. OBJETIVO: Nuestro objetivo fue estudiar el comportamiento de la CPP y sus mecanismos subyacentes en Ratas con infarto de miocardio. MÉTODOS: Seis semanas después de la oclusión coronaria, la contractilidad de los Músculos Papilares (MP) obtenidos a partir de Ratas sometidos a falsa cirurgia (C, n = 17), con infarto moderado (MMI, n = 10) y gran infarto (LMI, n = 14), fue evaluada después de pausas de estímulos de 10 a 60 segundos antes y después de la incubación con cloruro de litio (Li+) en substitución del cloruro de sodio o rianodina (Ry). La expresión proteica de SR Ca(2+)-ATPasa (SERCA2), intercambiador Na+/Ca2+ (NCX), fosfolamban (PLB) y fosfo-Ser (16)-PLB fue analizada por Western blotting. RESULTADOS: Los Ratas MMI presentaron potenciación de CPP reducida en comparación a los Ratas C. En oposición a la potenciación normal para Ratas C, fueron observadas decaimientos de fuerza post-reposo en los músculos de Ratas LMI. Además de eso, la Ry bloqueó la decaimiento o potenciación de PRC observada en Ratas LMI y C; el Li+ inhibió el NCX y convirtió la decaimiento en potenciación de CPP en Ratas LMI. Aunque los Ratas MMI y LMI hayan presentado disminución en el SERCA2 (72 ± 7% y 47 ± 9% de Ratas control, respectivamente) y expresión proteica de fosfo-Ser16-PLB (75 ± 5% y 46 ± 11%, respectivamente), la superexpresión del NCX (175 ± 20%) sólo fue observada en los músculos de Ratas LMI. CONCLUSIÓN: Nuestros resultados mostraron, por primera vez, que el remodelado miocárdico post-IAM en Ratas puede cambiar la potenciación regular para decaimiento post-reposo, afectando las proteínas de manejo del Ca(2+) en miocitos.


Subject(s)
Animals , Rats , Calcium-Binding Proteins/metabolism , Calcium/metabolism , Myocardial Contraction/drug effects , Myocardial Infarction/metabolism , Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism , Sodium-Calcium Exchanger/metabolism , Ventricular Remodeling/physiology , Disease Models, Animal , Lithium Chloride/pharmacology , Myocardial Contraction/physiology , Myocardial Infarction/classification , Myocytes, Cardiac/metabolism , Papillary Muscles/metabolism , Random Allocation , Rats, Wistar , Ryanodine/pharmacology
11.
Rev. bras. cir. cardiovasc ; 27(1): 110-116, jan.-mar. 2012. ilus, tab
Article in English | LILACS | ID: lil-638658

ABSTRACT

BACKGROUND: There is a growing need to improve myocardial protection, which will lead to better performance of cardiac operations and reduce morbidity and mortality. Therefore, the objective of this study was to compare the efficacy of myocardial protection solution using both intracellular and extracellular crystalloid type regarding the performance of the electrical conduction system, left ventricular contractility and edema, after being subjected to ischemic arrest and reperfusion. METHODS: Hearts isolated from male Wistar (n=32) rats were prepared using Langendorff method and randomly divided equally into four groups according the cardioprotective solutions used Krebs-Henseleit-Buffer (KHB), Bretschneider-HTK (HTK), St. Thomas-1 (STH-1) and Celsior (CEL). After stabilization with KHB at 37ºC, baseline values (control) were collected for heart rate (HR), left ventricle systolic pressure (LVSP), maximum first derivate of rise left ventricular pressure (+dP/dt), maximum first derivate of fall left ventricular pressure (-dP/dt) and coronary flow (CF). The hearts were then perfused at 10ºC for 5 min and kept for 2 h in static ischemia at 20ºC in each cardioprotective solution. Data evaluation was done using analysis of variance in completely randomized One-Way ANOVA and Tukey's test for multiple comparisons. The level of statistical significance chosen was P<0.05. RESULTS: HR was restored with all the solutions used. The evaluation of left ventricular contractility (LVSP, +dP/ dt and -dP/dt) showed that treatment with CEL solution was better compared to other solutions. When analyzing the CF, the HTK solution showed better protection against edema. CONCLUSION: Despite the cardioprotective crystalloid solutions studied are not fully able to suppress the deleterious effects of ischemia and reperfusion in the rat heart, the CEL solution had significantly higher results followed by HTK>KHB>STH-1.


INTRODUÇÃO: Existe crescente necessidade de aprimorar a proteção miocárdica, para melhor desempenho das operações cardíacas e diminuição da morbimortalidade. Portanto, o objetivo deste estudo foi comparar a eficácia da proteção miocárdica usando tanto solução cristaloide tipo intracelular como extracelular quanto ao desempenho do sistema de condução elétrica, contratilidade do ventrículo esquerdo e edema, após parada isquêmica e posterior reperfusão. MÉTODOS: Corações isolados de ratos Wistar foram montados em Langendorff e aleatoriamente divididos em quatro grupos. de acordo com as soluções cardioprotetoras utilizadas Krebs-Henseleit-Buffer (KHB), Bretschneider-HTK (HTK), St. Thomas-1(STH-1) e Celsior (CEL). Após a estabilização com KHB a 37ºC, valores basais (controle) foram coletados para frequência cardíaca (FC), pressão sistólica do ventrículo esquerdo (PSVE), derivada máxima de aumento da pressão ventricular esquerda (+dP/dt), derivada máxima de queda da pressão ventricular esquerda (-dP/dt) e fluxo coronariano (FCo). Os corações foram então perfundidos a 10ºC por 5 min e mantidos por 2 h em isquemia estática a 20ºC em cada solução cardioprotetora. Avaliação dos dados foi por análise de variância inteiramente casualizados em One-Way ANOVA e teste de Tukey para comparações múltiplas. O nível de significância estatística escolhido foi P<0,05. RESULTADOS: Houve recuperação da FC com todas as soluções utilizadas. A avaliação da contratilidade ventricular esquerda (PSVE, +dP/dt e -dP/dt) demonstrou que o tratamento com a solução CEL foi melhor em comparação às outras soluções. Ao analisar o CF, a solução HTK indicou melhor proteção contra edema. CONCLUSÃO: Apesar das soluções cristaloides cardioprotetoras estudadas não serem capazes de suprimir os efeitos deletérios da isquemia e reperfusão no coração de ratos, a solução CEL apresentou resultado superior seguido por HTK>KHB>STH-1.


Subject(s)
Animals , Male , Rats , Cardioplegic Solutions/pharmacology , Edema, Cardiac/pathology , Heart Transplantation , Heart Conduction System/drug effects , Isotonic Solutions/pharmacology , Myocardial Contraction/drug effects , Ventricular Function, Left/drug effects , Analysis of Variance , Bicarbonates/pharmacology , Calcium Chloride/pharmacology , Disaccharides/pharmacology , Electrolytes/pharmacology , Glucose/pharmacology , Glutamates/pharmacology , Glutathione/pharmacology , Heart Arrest, Induced/methods , Hemodynamics/drug effects , Histidine/pharmacology , Models, Animal , Magnesium/pharmacology , Mannitol/pharmacology , Myocardial Reperfusion Injury/prevention & control , Organ Preservation/methods , Potassium Chloride/pharmacology , Procaine/pharmacology , Random Allocation , Rats, Wistar , Sodium Chloride/pharmacology , Tromethamine/pharmacology
12.
Clinics ; 67(5): 489-496, 2012. graf, tab
Article in English | LILACS | ID: lil-626346

ABSTRACT

OBJECTIVES: Tension cost, the ratio of myosin ATPase activity to tension, reflects the economy of tension development in the myocardium. To evaluate the mechanical advantage represented by the tension cost, we studied papillary muscle contractility and the activity of myosin ATPase in the left ventricles in normal and pathophysiological conditions. METHODS: Experimental protocols were performed using rat left ventricles from: (1) streptozotocin-induced diabetic and control Wistar rats; (2) N-nitro-L-arginine methyl ester (L-NAME) hypertensive and untreated Wistar rats; (3) deoxycorticosterone acetate (DOCA) salt-treated, nephrectomized and salt- and DOCA-treated rats; (4) spontaneous hypertensive rats (SHR) and Wistar Kyoto (WKY) rats; (5) rats with myocardial infarction and shamoperated rats. The isometric force, tetanic tension, and the activity of myosin ATPase were measured. RESULTS: The results obtained from infarcted, diabetic, and deoxycorticosterone acetate-salt-treated rats showed reductions in twitch and tetanic tension compared to the control and sham-operated groups. Twitch and tetanic tension increased in the N-nitro-L-arginine methyl ester-treated rats compared with the Wistar rats. Myosin ATPase activity was depressed in the infarcted, diabetic, and deoxycorticosterone acetate salt-treated rats compared with control and sham-operated rats and was increased in N-nitro-L-arginine methyl ester-treated rats. These parameters did not differ between SHR and WKY rats. In the studied conditions (e.g., post-myocardial infarction, deoxycorticosterone acetate salt-induced hypertension, chronic N-nitro-L-arginine methyl ester treatment, and streptozotocin-induced diabetes), a positive correlation between force or plateau tetanic tension and myosin ATPase activity was observed. CONCLUSION: Our results suggest that the myocardium adapts to force generation by increasing or reducing the tension cost to maintain myocardial contractility with a better mechanical advantage.


Subject(s)
Animals , Male , Rats , Diabetes Mellitus, Experimental/physiopathology , Hypertension/physiopathology , Myocardial Contraction/physiology , Myocardial Infarction/physiopathology , Papillary Muscles/physiopathology , Ventricular Function, Left , Ventricular Myosins/metabolism , Desoxycorticosterone/analogs & derivatives , Diabetes Mellitus, Experimental/chemically induced , Enzyme Inhibitors , Hypertension/chemically induced , Myocardial Contraction/drug effects , Nephrectomy , NG-Nitroarginine Methyl Ester , Rats, Inbred SHR , Rats, Inbred WKY
13.
Yonsei Medical Journal ; : 204-212, 2012.
Article in English | WPRIM | ID: wpr-145830

ABSTRACT

PURPOSE: Despite the fact that desflurane prolongs the QTC interval in humans, little is known about the mechanisms that underlie these actions. We investigated the effects of desflurane on action potential (AP) duration and underlying electrophysiological mechanisms in rat ventricular myocytes. MATERIALS AND METHODS: Rat ventricular myocytes were enzymatically isolated and studied at room temperature. AP was measured using a current clamp technique. The effects of 6% (0.78 mM) and 12% (1.23 mM) desflurane on transient outward K+ current (I(to)), sustained outward current (I(sus)), inward rectifier K+ current (I(KI)), and L-type Ca2+ current were determined using a whole cell voltage clamp. RESULTS: Desflurane prolonged AP duration, while the amplitude and resting membrane potential remained unchanged. Desflurane at 0.78 mM and 1.23 mM significantly reduced the peak I(to) by 20+/-8% and 32+/-7%, respectively, at +60 mV. Desflurane (1.23 mM) shifted the steady-state inactivation curve in a hyperpolarizing direction and accelerated inactivation of the current. While desflurane (1.23 mM) had no effects on I(sus) and I(KI), it reduced the L-type Ca2+ current by 40+/-6% (p<0.05). CONCLUSION: Clinically relevant concentrations of desflurane appear to prolong AP duration by suppressing Ito in rat ventricular myocytes.


Subject(s)
Action Potentials/drug effects , Anesthetics, Inhalation/pharmacology , Animals , Calcium Channels, L-Type/physiology , Heart Conduction System/drug effects , Heart Ventricles/drug effects , Isoflurane/analogs & derivatives , Myocardial Contraction/drug effects , Myocytes, Cardiac/drug effects , Patch-Clamp Techniques , Potassium Channels/physiology , Rats , Rats, Sprague-Dawley
14.
Arq. bras. cardiol ; 97(4): 324-331, out. 2011. ilus, tab
Article in Portuguese | LILACS | ID: lil-606435

ABSTRACT

FUNDAMENTO: O tramadol é um analgésico de ação central cujo mecanismo de ação envolve a ativação de um receptor opioide. Anteriormente, mostramos que o tramadol e seus enantiômeros apresentavam um efeito inotrópico negativo sobre o músculo papilar no qual o (+)-enantiômero era mais potente que (-)- e (±)-tramadol. OBJETIVO: No presente trabalho, investigamos os efeitos do tramadol e seus enantiômeros na corrente de cálcio tipo L (I Ca-L). MÉTODOS: Os experimentos foram realizados em miócitos ventriculares isolados de ratos Wistar utilizando a técnica de patch-clamp com configuração de célula inteira. RESULTADOS: O tramadol (200 µM) reduziu a amplitude de pico do I Ca-L em potenciais de 0 a +50 mV. Em 0 mV, a I Ca-L foi reduzida em 33,7 ± 7,2 por cento. (+)- e (-)-tramadol (200 µM) produziram uma inibição semelhante da I Ca-L, na qual a amplitude do pico foi reduzida em 64,4 ± 2,8 por cento e 68,9 ± 5,8 por cento, respectivamente a 0 mV (P > 0,05). O tramadol, (+)- e (-)-tramadol mudaram a inativação de estado estacionário de I Ca-L para potenciais de membrana mais negativos. Além disso, tramadol e (+)-tramadol alteraram significativamente a curva de recuperação dependente de tempo da I Ca-L para a direita e reduziram a recuperação de I Ca-L da inativação. A constante de tempo foi aumentada de 175,6 ± 18,6 a 305,0 ± 32,9 ms (P < 0,01) para o tramadol e de 248,1 ± 28,1 ms para 359,0 ± 23,8 ms (P < 0,05) para o (+)-tramadol. O agonista do receptor µ-opioide (DAMGO) não tem nenhum efeito na I Ca-L. CONCLUSÃO: A inibição da I Ca-L induzida por tramadol e seus enantiômeros não teve relação com a ativação de receptores opioides e poderia explicar, pelo menos em parte, seu efeito inotrópico negativo cardíaco.


BACKGROUND: Tramadol is a centrally acting analgesic, whose mechanism of action involves opioid-receptor activation. Previously, we have shown that tramadol and its enantiomers had a negative inotropic effect on the papillary muscle in which the (+)-enantiomer is more potent than (-)- and (±)-tramadol. OBJECTIVE: In this study, we investigated the effects of tramadol and its enantiomers on L-type calcium current (I Ca-L). RESULTS: Tramadol (200 µM) reduced the peak amplitude of I Ca-L at potentials from 0 to +50 mV. At 0 mV, I Ca-L was reduced by 33.7 ± 7.2 percent. (+)- and (-)-tramadol (200 µM) produced a similar inhibition of I Ca-L, in which the peak amplitude was reduced by 64.4 ± 2.8 percent and 68.9 ± 5.8 percent, respectively at 0 mV (p > 0.05). Tramadol, (+)- and (-)-tramadol shifted the steady-state inactivation of I Ca-L to more negative membrane potentials. Also, tramadol and (+)-tramadol markedly shifted the time-dependent recovery curve of I Ca-L to the right and slowed down the recovery of I Ca-L from inactivation. The time constant was increased from 175.6 ± 18.6 to 305.0 ± 32.9 ms (p < 0.01) for tramadol and from 248.1 ± 28.1 ms to 359.0 ± 23.8 ms (p < 0.05) for (+)-tramadol. The agonist of µ-opioid receptor DAMGO had no effect on the I Ca-L. CONCLUSION: The inhibition of I Ca-L induced by tramadol and its enantiomers was unrelated to the activation of opioid receptors and could explain, at least in part, their negative cardiac inotropic effect.


Subject(s)
Animals , Male , Rats , Analgesics, Opioid/pharmacology , Calcium Channels, L-Type/drug effects , Myocardial Contraction/drug effects , Myocytes, Cardiac/drug effects , Papillary Muscles/drug effects , Tramadol/pharmacology , Analysis of Variance , Depression, Chemical , Models, Animal , Patch-Clamp Techniques , Rats, Wistar , Tramadol/analogs & derivatives
15.
Rev. bras. cir. cardiovasc ; 26(3): 433-439, jul.-set. 2011.
Article in English | LILACS | ID: lil-624526

ABSTRACT

OBJECTIVE: To evaluate pantoprazole effect in the functional recovery of isolated hearts of rats, submitted to ischemia and reperfusion with and without ischemic preconditioning. METHODS: In four groups of eight Wistar breed rats, the hearts were removed after anesthesia and perfused with Krebs-Henseleit solution (95% O2, 5% CO2, 37ºC). GI, GII, GIII and GIV hearts were submitted to ischemia (20 min) and reperfusion (30 min). In GII and GIV, preconditioning was performed with 5 min of ischemia and 5 min of reperfusion before 20 min of the ischemia period induction. In GIII and GIV pantoprazole 100 mg was done before a 20 min-period of ischemia induction. Heart Rate (HR), Coronary Flow (CoF), Systolic Pressure (SP), +dP/dt and -dP/dt were registered before (t0) and after reperfusion (t30). Kruskal-Wallis (P<0.05) test was used. RESULTS: There were no differences (P>0.05) between groups among HR and CoF values. Differences occurred between groups, I and II, III and IV at t30 with SP reduced for 32% mean value in GI, 65% GII, 65% GIII, and 73% GIV; The t30 + dP/dtmax were 34% in GI, 61% GII, 63% GIII and 72% GIV. The t30 -dP/dtmax were GI 28%, GII 63%, GIII 75 % and GIV 75%; (P<0.05). There were no significant differences in the SP, +dP/dtmax, and -dP/dtmax between Groups II, III and IV results. CONCLUSIONS: The administration of pantoprazole before induction of ischemia significantly protected the myocardial functional recovery with the results of SP, + dP / dtmax and dP/dtmax similar to the ischemic preconditioning against ischemia-reperfusion.


OBJETIVO: Avaliar o efeito do pantoprazol na recuperação funcional de corações isolados de ratos submetidos à isquemia e reperfusão com e sem pré-condicionamento isquêmico. MÉTODOS: Em quatro grupos de oito ratos Wistar, após anestesia os corações foram removidos e perfundidos com Krebs-Henseleit (95% O2, 5% CO2, 37ºC). Os corações de GI, GII, GIII e GIV foram submetidos a 20' de isquemia e 30'de reperfusão. Em GII e GIV realizou-se pré condicionamento com 5' de isquemia e 5' de reperfusão antes dos 20' de isquemia. Em GIII e GIV, pantoprazol 100mcg foram injetados imediatamente antes dos 20' de isquemia. Frequência cardíaca (FC), Fluxo Coronariano (FCo), Pressão Sistólica (PS), + dP/dt e -dP/dt foram registrados em (T0) e (t30). Estatística: Kruskal-Wallis (P <0,05). RESULTADOS: Não houve diferenças (P> 0,05) entre grupos nos valores de FC e de CFo. Diferenças (P <0,05) ocorreram entre GI e GII, GIII e GIV, com PS t30 reduzida para 32% GI, 65% GII, 65% GIII e 73% GIV. Em t30 + dP/dtmax 34% GI, 61% GII, 63% GIII e 72% GIV. A -dP/dtmax t30 GI 28%, GII 63%, GIII 75% e GIV 75%. Não houve diferença estatística (P< 0,05) nos valores de PS, +dP/dtmax e -dP/dtmax entre os GII, GIII e GIV. CONCLUSÕES: A administração do pantoprazol antes da indução da isquemia protegeu significativamente a recuperação funcional miocárdica com resultados de SP, +dP/ dtmax e -dP/dtmax semelhantes aos do pré-condicionamento isquêmico contra lesão de isquemia-reperfusão.


Subject(s)
Animals , Rats , Enzyme Inhibitors/pharmacology , Ischemic Preconditioning, Myocardial , Myocardial Ischemia/metabolism , Myocardial Reperfusion Injury/prevention & control , /pharmacology , Enzyme Inhibitors/adverse effects , Heart Rate/drug effects , Ischemic Preconditioning, Myocardial/methods , Models, Animal , Myocardial Contraction/drug effects , Random Allocation , Rats, Wistar , Recovery of Function/drug effects , /adverse effects
16.
Rev. bras. cir. cardiovasc ; 25(3): 388-392, jul.-set. 2010. ilus, tab
Article in Portuguese | LILACS | ID: lil-565006

ABSTRACT

OBJETIVO: Analisar efeitos do omeprazol na proteção da recuperação funcional de corações isolados de ratos submetidos à lesão de isquemia-reperfusão. MÉTODOS: Foram estudados 12 ratos Wistar, peso corpóreo médio de 280g. Após anestesia com injeção intra-abdominal de 10mg de cetamina e 2mg de xilazina, os corações foram removidos e mantidos em perfusão com solução Krebs-Henseleit (95 por centoO2 e 5 por cento CO2, 37ºC, 110-120mmHg de pressão de perfusão e pressão diastólica de 8 mmHg) em sistema Langendorff, modificado, descartável, modelo FCSFA-ServCor (Comex Ltda.). Os seis corações do Grupo I (GI) e os seis do Grupo II (GII) foram submetidos a 20 minutos de isquemia e 30 minutos de reperfusão. Nos corações do Grupo II, imediatamente antes da isquemia, foram administrados via perfusão coronária 200mcg de omeprazol. Foram controlados frequência cardíaca (FC), fluxo coronário (FCo), pressão sistólica (PS), +dP/dt e -dP/dt, após estabilização (t0) e no final da reperfusão (t30). Empregou-se método não paramétrico de Kruskal-Wallis (P<0,05) para análise estatística dos dados. RESULTADOS: Não ocorreram diferenças (P>0,05) entre os valores de FCo e FC nos dois grupos. No final do período de reperfusão (t30), foram significantes (P<0,05) as variações da PS reduzida para 28,0±3,6 por cento do valor inicial (t0) no Grupo I e para 79.0±5,9 por cento no Grupo II; a +dP/dtmax declinou para 31,0±5,6 por cento no GI, mantendo-se em 99,4±11,2 por cento (P<0,05) no GII e a -dP/dtmax declinou para 26,0±7,3 por cento no GI, mantendo-se em 82,0±2, 2 por cento no GII (P<0,05). CONCLUSÃO: A administração do omeprazol antes da indução da isquemia coronária protegeu significantemente a recuperação funcional do miocárdio.


OBJECTIVE: To evaluate the myocardium contractility alterations of isolated hearts of rats, submitted to ischemia and reperfusion with and without administration of the omeprazole. METHODS: Twelve Wistar breed rats with 270g mean body weight was studied. After anesthesia by intraperitoneal injection of ketamine 10mg and xylazine 2mg, their hearts were removed and perfused with Krebs-Henseleit solution (95 percent of O2 and 5 percent of CO2, 37ºC, 110-120 mmHg perfusion pressure, 8 mmHg ventricular diastolic pressure) in the São Francisco de Assis disposable Langendorff system model Comex Ltda, MG. The six hearts of Group I (GI) and of the Group II (GII) were submitted to 20 min ischemia and 30 min reperfusion. In GII hearts, intracoronary injection of omeprazole 200 mcg was done immediately before the ischemia period induction. The following parameters were registered after the stabilization period (t0), and after the reperfusion period (t30): heart rate (HR), coronary flow (CoF), systolic pressure (SP), +dP/dt and -dP/dt. The Kruskal-Wallis test (P<0.05) was applied to statistical analysis. RESULTS: There were no significant differences (P>0.05) between groups among HR and CoF values. Differences (P<0.05) occurred between groups, I e II after the reperfusion period (t30) regarding systolic pressure reduced for 28.0±3.6 percent in the control group GI and for 79.0±5.9 percent in GII; The +dP/dtmax declined to be only 31.0±5.6 percent in GI, preserving 99.4±11.2 percent values in GII (P<0.05). The t30 -dP/dtmax values were GI 26.0±7.3 percent and GII 82.0±2.2 percent (P<0.05). CONCLUSION: The omeprazole administration before ischemia induction significantly protected the myocardium function recovery.


Subject(s)
Animals , Rats , Enzyme Inhibitors/therapeutic use , Myocardial Contraction/drug effects , Myocardial Reperfusion Injury/drug therapy , Omeprazole/therapeutic use , Enzyme Inhibitors/pharmacology , Heart Rate/drug effects , Omeprazole/pharmacology , Rats, Wistar , Recovery of Function/drug effects
17.
Braz. j. med. biol. res ; 42(10): 902-911, Oct. 2009. ilus, tab
Article in English | LILACS | ID: lil-526185

ABSTRACT

Myocardial infarction leads to compensatory ventricular remodeling. Disturbances in myocardial contractility depend on the active transport of Ca2+ and Na+, which are regulated by Na+-K+ ATPase. Inappropriate regulation of Na+-K+ ATPase activity leads to excessive loss of K+ and gain of Na+ by the cell. We determined the participation of Na+-K+ ATPase in ventricular performance early and late after myocardial infarction. Wistar rats (8-10 per group) underwent left coronary artery ligation (infarcted, Inf) or sham-operation (Sham). Ventricular performance was measured at 3 and 30 days after surgery using the Langendorff technique. Left ventricular systolic pressure was obtained under different ventricular diastolic pressures and increased extracellular Ca2+ concentrations (Ca2+e) and after low and high ouabain concentrations. The baseline coronary perfusion pressure increased 3 days after myocardial infarction and normalized by 30 days (Sham 3 = 88 ± 6; Inf 3 = 130 ± 9; Inf 30 = 92 ± 7 mmHg; P < 0.05). The inotropic response to Ca2+e and ouabain was reduced at 3 and 30 days after myocardial infarction (Ca2+ = 1.25 mM; Sham 3 = 70 ± 3; Inf 3 = 45 ± 2; Inf 30 = 29 ± 3 mmHg; P < 0.05), while the Frank-Starling mechanism was preserved. At 3 and 30 days after myocardial infarction, ventricular Na+-K+ ATPase activity and contractility were reduced. This Na+-K+ ATPase hypoactivity may modify the Na+, K+ and Ca2+ transport across the sarcolemma resulting in ventricular dysfunction.


Subject(s)
Animals , Male , Rats , Myocardial Contraction/physiology , Myocardial Infarction/physiopathology , Sodium-Potassium-Exchanging ATPase/metabolism , Ventricular Function, Left/physiology , Cardiotonic Agents/pharmacology , Myocardial Contraction/drug effects , Myocardial Infarction/enzymology , Ouabain/pharmacology , Rats, Wistar , Vascular Resistance/drug effects , Vascular Resistance/physiology , Ventricular Function, Left/drug effects
18.
Acta cir. bras ; 24(3): 173-176, May-June 2009. graf, tab
Article in English | LILACS | ID: lil-515797

ABSTRACT

PURPOSE: To study the effects of benzodiazepine midazolam in the coronary flow (Cflo), cardiac frequency (CF) and myocardial contractility in isolated hearts of rats subjected to ischemic preconditioning (IPC). METHODS: 30 Wistar rats were used, undistinguished by gender. After anesthesia with ethyl ether, the hearts were put into perfusion (Krebs-Henseleit solution, 95 percent O2 and 5 percent CO2, 37°C, 110-120mmHg), in disposable Langendorff type system. Five groups of six animals were constituted: GI- Control; GII- Ischemia; GIII- IPC; GIV- Ischemia + 100mcg of midazolam; GV- IPC + 100mcg of midazolam. After stabilization (t0), and on times t5, t10, t15, t20 and t25, CF, Cflo, systolic pressure (SP) and diastolic pressure (DP) and dP/dt were recorded. DP was maintained at 5 ± 2 mmHg. The statistical method ANOVA and Tukey Test were employed for p < 0.05. RESULTS: No significant variations have occurred between Cflo and CF. On Pd/td, differences have occurred (p<0.05) between groups I and II (respectively 94.7±23.0 and 62.3±12.1 percent). The preconditioning (GIII), improved significantly the results in the group II (respectively 62.3±12.1 and 87.1±12.4 percent). The decrease in dP/dt in group II was not prevented by midazolam (GIV) (62.3±12,1 and 60.5±15.8 percent). In group III, dP/dt was 87.1±12.4 percent, whereas in group V, only 55.5±17.2 percent (p<0.05) CONCLUSION: Midazolam, when administered before the ischemia, was unable to prevent the ischemic deterioration of the myocardium. When administered before the preconditioning, it has abolished its protective effect.


OBJETIVO: Estudar os efeitos do benzodiazepínico midazolam no fluxo coronariano (Fco), freqüência cardíaca (FC) e contratilidade miocárdica de corações isolados de ratos submetidos ao precondicionamento isquêmico (PCI). MÉTODOS: Foram utilizados 30 ratos Wistar sem distinção de sexo. Após anestesia com éter etílico, os corações foram postos em perfusão (solução de Krebs-Henseleit, 95 por cento de O2 e 5 por cento de CO2, 37°C, 110-120mmHg), em sistema tipo Langendorff descartável. Foram constituídos cinco grupos de seis animais: GI- Controle; GII- Isquemia; GIII- PCI; GIV- Isquemia + 100mcg de midazolam ; GV- PCI + 100mcg de midazolam. Após estabilização (t0), e nos tempos t5, t10, t15, t20 e t25, foram registrados a FC, Fco, pressões sistólica (PS) e diastólica (PD) e dP/dt. A PD foi mantida em 5 ± 2 mmHg. Empregou-se método estatístico ANOVA e Teste de Tukey para p < 0,05. RESULTADOS: Não ocorreram variações significantes entre FCo e FC. Na dP/dt, ocorreram diferenças (p<0,05) entre os grupos I e II (respectivamente 94,7±23,0 e 62,3±12,1 por cento). O precondicionamento (GIII), melhorou significantemente os resultados do grupo II (respectivamente 62,3±12,1 e 87,1±12,4 por cento). A queda da dP/dt no grupo II não foi impedida pelo midazolam (GIV) ( 62,3±12,1 e 60,5±15,8 por cento). No grupo III a dP/dT foi 87,1±12,4 por cento, sendo que no grupo V, apenas 55,5±17,2 por cento (p<0,05). CONCLUSÃO: O midazolan quando administrado antes da isquemia não impediu deterioração isquêmica do miocárdio. Quando administrado antes do precondicionamento aboliu seu efeito protetor.


Subject(s)
Animals , Female , Male , Rats , Anti-Anxiety Agents/pharmacology , Coronary Circulation/drug effects , Heart Rate/drug effects , Ischemic Preconditioning, Myocardial/methods , Midazolam/pharmacology , Myocardial Contraction/drug effects , Disease Models, Animal , Myocardial Reperfusion Injury/prevention & control , Rats, Wistar
19.
Rev. bras. cir. cardiovasc ; 24(1): 23-30, Jan.-Mar. 2009. ilus, tab, graf
Article in Portuguese | LILACS | ID: lil-515582

ABSTRACT

OBJETIVO: Avaliar se a N-Acetilcisteína (NAC) altera o Precondicionamento Isquêmico (PC) em corações isolados de ratos usando apenas um ciclo de PC. MÉTODOS: Freqüência Cardíaca (FC), Fluxo Coronariano (FLC) e Contratilidade Miocárdica (dP/dt) foram registradas em 30 corações de ratos Wistar. Após anestesia, os corações foram perfundidos em sistema de Langendorff com solução de Krebs-Hensleit (K-H), equilibrada (95 por cento de O2 e 5 por cento de CO2). GI: Controle (n=6); GII: 20 min. isquemia (n=6); GIII: PC (n=6); GIV 50 µg/ml/min NAC antes do PC (n =6); GV: 100 µg/ml/min NAC antes do PC (n=6). Todos os parâmetros foram mensurados após 15 minutos de estabilização (T0) e T3, T5, T10, T15, T20, T25 e T30 minutos de reperfusão. Significância estatística foi considerada quando P<0,05. RESULTADOS: Foram observadas alterações na FC comparando GI com GII em T20 e T25 e comparando GI com GIII e GIV com GV em T10 e T20 (P<0,05). FLC foi diferente comparando GI com GII em T3 e T5, GI com GIV em T10 e GI com GV em T10 e T25 (P<0,05). dP/dt foi semelhante comparando GIII com GI e GV. GIII apresentou maior dP/dt que GIV, mas sem diferença estatística (P>0,05). dP/dt foi maior no GV comparado com GIV, mas com diferença estatisticamente significativa somente em T30. CONCLUSÃO: Os corações precondicionados tiveram melhor dP/dt, sendo alteradas pelo uso de NAC no GIV e não alteradas no GV.


OBJECTIVE: The aim of this study is to assess if N-Acetylcysteine (NAC) changes the Ischemic Preconditioning (IP) in isolated rat hearts using only one cycle of IP. METHODS: Heart Rate (HR), Coronary Flow (CF) and Myocardial Contractility (dP/dt) were registered in 30 Wistar rat's hearts. After anesthesia the hearts were removed and perfused with Krebes-Hensleit equilibrated solution with 95 percent of O2 and 5 percent of CO2 according Langendorff's method. GI: Control (n=6); GII: 20 min. ischemia (n=6); GIII: IP (n=6); GIV 50 µg/ml/min NAC before IP (n =6); GV: 100 µg/ ml/min NAC before IP (n=6). Parameters were measured after 15 min. of stabilization (T 0) and T3, T5, T10, T15, T20, T25 and T30 min. after reperfusion. Statistical significance was considered when P<0.05. RESULTS: There were changes on HR comparing GI with GII at T20 and T25 and comparing GI with GIII, GIV with GV at T10 and T20 (P<0.05). CF was different comparing GI with GII at T3 and T5, GI with GIV at T10 and GI with GV at T10 and T25 (P<0.05). Myocardial Contractility was similar comparing GIII with GI and GV. GIII had higher dP/dt than GIV but without statistical difference (P>0.05). dP/dt was higher in GV than GIV but with statistically significant difference only at T30. CONCLUSION: dP/dt was better in preconditioned hearts and was changed if using NAC in GIV. The use of NAC didn't change the effects of preconditioning on myocardial contractility in GV.


Subject(s)
Animals , Rats , Acetylcysteine/administration & dosage , Coronary Circulation/drug effects , Free Radical Scavengers/administration & dosage , Heart Rate/drug effects , Ischemic Preconditioning, Myocardial/methods , Myocardial Contraction/drug effects , Analysis of Variance , Models, Animal , Rats, Wistar , Time Factors
20.
Pakistan Journal of Medical Sciences. 2009; 25 (2): 289-292
in English | IMEMR | ID: emr-92421

ABSTRACT

Hemorrhagic shock and resuscitation is well known to result in myocardial dysfunction and injury. Stimulation of the Na[+] -H[+] exchanger plays an important role in the pathway of myocardial injury. The purpose of the present study was to examine the protective effects of blocking the cardiac Na[+] -H[+] exchange, using 100mM ethyl-isopropyl amiloride [EIPA], a specific Na[+] -H[+] exchanger blocker, on myocardial contractile function on ex vivo resuscitation of isolated rat heart following one hour of hemorrhagic shock. Sprague- Dawley rats were assigned to hemorrhage, hemorrhage + EIPA, sham hemorrhage and sham hemorrhage + EIPA groups. Rats were hemorrhaged for one hour. Hearts were harvested and ex vivo treated and resuscitated by perfused in the Langendorff System. Myocardial function was determined. The results showed that inhibition of the Na[+] -H[+] exchanger using EIPA improved the post-resuscitation myocardial contractile function. Blocking the Na[+] -H[+] exchanger using 100mM EIPA following 60 minutes of hemorrhagic shock improved myocardial function


Subject(s)
Animals, Laboratory , Shock, Hemorrhagic/complications , Amiloride/pharmacology , Sodium-Hydrogen Exchangers/antagonists & inhibitors , Resuscitation , Rats , Hemorrhage , Myocardial Contraction/drug effects , Amiloride/analogs & derivatives
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