Endothelin-B receptors and ventricular arrhythmogenesis in the rat model of acute myocardial infarction (Journal article)

Oikonomidis, D. L./ Tsalikakis, D. G./ Baltogiannis, G. G./ Tzallas, A. T./ Xourgia, X./ Agelaki, M. G./ Megalou, A. J./ Fotopoulos, A./ Papalois, A./ Kyriakides, Z. S./ Kolettis, T. M.

The arrhythmogenic effects of endothelin-1 (ET-1) are mediated via ETA-receptors, but the role of ETB-receptors is unclear. We examined the pathophysiologic role of ETB-receptors on ventricular tachyarrhythmias (VT/VF) during myocardial infarction (MI). MI was induced by coronary ligation in two animal groups, namely in wild-type (n = 63) and in ETB-receptor-deficient (n = 61) rats. Using a telemetry recorder, VT/VF episodes were evaluated during phase I (the 1st hour) and phase II (2-24 h) post-MI, with and without prior beta-blockade. Action potential duration at 90% repolarization (APD90) was measured from monophasic epicardial recordings and indices of sympathetic activation were assessed using fast-Fourier analysis of heart rate variability. Serum epinephrine and norepinephrine were measured with radioimmunoassay. MI size was similar in the two groups. There was a marked temporal variation in VT/VF duration; during phase I, it was higher (p = 0.0087) in ETB-deficient (1,519 +/- 421 s) than in wild-type (190 +/- 34 s) rats, but tended (p = 0.086) to be lower in ETB-deficient (4.2 +/- 2.0 s) than in wild-type (27.7 +/- 8.0 s) rats during phase II. Overall, the severity of VT/VF was greater in ETB-deficient rats, evidenced by higher (p = 0.0058) mortality (72.0% vs. 32.1%). There was a temporal variation in heart rate and in the ratio of low- to high-frequency spectra, being higher (<0.001) during phase I, but lower (p < 0.05) during phase II in ETB-deficient rats. Likewise, 1 h post-MI, serum epinephrine (p = 0.025) and norepinephrine (p < 0.0001) were higher in ETB-deficient (4.20 +/- 0.54, 14.24 +/- 1.39 ng/ml) than in wild-type (2.30 +/- 0.59, 5.26 +/- 0.67 ng/ml) rats, respectively. After beta-blockade, VT/VF episodes and mortality were similar in the two groups. The ETB-receptor decreases sympathetic activation and arrhythmogenesis during the early phase of MI, but these effects diminish during evolving MI.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Επιστημών Υγείας. Τμήμα Ιατρικής
Keywords: Action Potentials,Adrenergic beta-Antagonists/therapeutic use,Animals,Catecholamines/blood,Electrocardiography,Heart Rate,Myocardial Infarction/complications/*metabolism/pathology/physiopathology,Myocardium/pathology,Rats,Receptor, Endothelin B/genetics/*metabolism,Tachycardia, Ventricular/etiology/*metabolism/prevention & control,Ventricular Dysfunction, Left,Ventricular Fibrillation/etiology/*metabolism/prevention & control
URI: http://olympias.lib.uoi.gr/jspui/handle/123456789/21963
ISSN: 1435-1803
Link: http://www.ncbi.nlm.nih.gov/pubmed/19838761
Appears in Collections:Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

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