Alteraçães ponderais, hemodinâmicas e da função vascular do leito arterial caudal em ratas sete dias após o infarto do miocárdio
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Data
2009-01-01
Autores
Baldo, Thais de Oliveira Faria
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Universidade Federal do Espírito Santo
Resumo
Infarct area (AI) is an important determinant to heart failure (IC) development. However, studies from our laboratory have been shown that IC nor always correlates with AI. The aim of this study was to evaluate the IC development at 7 days after myocardial infarction (IM), and its consequence on vascular reactivity in the rat tail bed. Female Wistar rats were divided in Control group (CT); fictitious surgery (SHAM); and a group that was submitted to myocardial infarction (INF). Later, the INF group was subdivided in those developed (INFIC) or not (INF) IC. Seven days later, animals were anesthetized and catheterized to assess blood pressure and left ventricular function. After that, the vascular tail bed was removed and perfused under constant flow (2.5 mL/min). Alterations in the mean perfusion pressure (PPM) were acquire after concentration-response curve to phenilephrine (FE, 0.0001-300µg), before and after CHAPS-induced endothelial damage. To evaluate basal nitric oxide (NO) release, L-NAME was used in the presence of FE. To evaluate the dependent or independent relaxation, crescent concentration of acetilcholine (ACh) and sodium nitroprusside (NPS) were perfused after contraction with KCl (65mM). Data are shown as mean ± the standard error of mean, and statistical significance set at P<0.05. Seven days after, animals from INF-IC group showed decreased body weight (PC) (CT: 14.5±2.73; SHAM: 8.14±2.24; INF: - 4.06±2.65; INF-IC: -23.3±4.96g; P<0.05), increased lung/PC ratio (CT: 5.5±0.64; SHAM: 5.5±0.22; INF: 8.44±0.62; INF-IC: 9.90±0.91mg/g; P<0.05) and right ventricle/PC ratio (CT: 0.45±0.03; SHAM: 0.57±0.06; INF: 0.68±0.04; INF-IC: 0.78±0.06mg/g; P<0.05) when compared to other groups. Moreover, increased values for left ventricular end-diastolic pressure (PDFVE) were evidenced in INF-IC group as compared to the others (CT: 1.72±0.8; SHAM: 1.6±0.5; INF: 4.48±0.5; INF-IC: 14.5±1.3mmHg; P<0.05). AI was similar between infarcted groups (INF: 35.8±1.2; INF-IC: 38.8±2.3%; P>0.05). Furthermore, variation in the PC during the seven days correlates with PDFVE (r= -0.592; P<0.05). In the vascular tail bed, INF-IC group showed reduced maximal response (Rmáx) to FE (330.4±13.4 mmHg) as compared to other groups (CT: 423.2±25.4; SHAM: 403.6±28; IM: 425.5±30.4; P<0.05). Basal NO release acquire in the INF-IC group (13.35 ± 2.31) was significantly better as compared to other groups (CT 7.40 ± 1.36; SHAM 7.23 ± 0.8; INF 3.77 ± 0.7; P< 0.05). The relaxation mediated by Ach was reduced in SHAM and INF groups (SHAM: 50.0±2.8; INF: 48.4±2.7 %) as compared to CT and INF-IC groups (CT: 69.1±4.0; INF-IC: 66.9±3.4%; P<0.05). We conclude that seven days after IM is possible to identify animals that, with the same AI, develop or not the IC. Moreover, these animals depict different patterns of vascular response due, at least in part, to a better endothelial NO bioavailability.
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Palavras-chave
Infarto do miocárdio , Insuficiência cardíaca , Reatividade vascular , Ratas