β2-Adrenoceptors Antiarrhythmic Effects in Wild Type Mice Fed a Cholesterol-Enriched Diet

The systematic intake of an unbalanced diet is an important risk factor for cardiovascular diseases, the leading cause of death in the entire world. Most of the studies address this issue using genetically manipulated mice. This study aims to investigate the effect of the intake of a cholesterol-enriched diet on cardiac and hemodynamic parameters in conscious wild type mice. Twenty male, three-month-old C57BL/6 mice were distributed in two groups: (CTL) control, with mice receiving standard commercial chow and (CHO) cholesterol group, with mice receiving a cholesterol-enriched diet during 15 days. Catheters were implanted in the carotid artery and jugular vein for blood pressure and heart rate recording and drugs administration. Electrodes were implanted for electrocardiogram recording and spectral analysis of heart rate variability. Glucose, cholesterol, and triglycerides were determined in blood samples and histopathological analysis of the aorta was performed. Serum cholesterol and glucose, mean arterial pressure and heart rate were higher in CHO than CTL mice. CHO mice also exhibited predominance of sympathetic over parasympathetic tonus to the heart, and higher responsiveness to the chronotropic effect of isoproterenol. Arrhythmic episodes, present only in the CHO mice, were cancelled by metoprolol and exacerbated by ICI118,551. It is concluded that the intake of high cholesterol diet causes hypertension and heart rhythm irregularities. Because those effects are exacerbated by the blockade of β2-adrenergic receptor and attenuated by the blockade of β1-adrenergic receptor, data highlights a possible antiarrhythmic protective role played by β2-AR subtype. *Corresponding author: Regina Celia Spadari, MD, PhD, Biology of Stress Laboratory, Biosciences Department, Rua Silva Jardim, 136 Vila Matias, Santos SP, 11015-020, Brazil, Tel: +55-13-3878 3827; E-mail: regina.spadari@unifesp.br Received July 29, 2016; Accepted September 21, 2016; Published September 26, 2016 Citation: Ternes SC, Souza LED, Cruz PL, Mostarda CT, Irigoyen MCC, et al. (2016) β2-Adrenoceptors Antiarrhythmic Effects in Wild Type Mice Fed a Cholesterol-Enriched Diet. Cardiovasc Pharm Open Access 5: 196. doi: 10.4172/2329-6607.1000196 Copyright: © 2016 Ternes SC, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. cardiac parameters of non-genetically manipulated mice, especially the role played by the β2-AR subtype in those processes. Material and Method Animals The experimental protocols were approved by the Institutional Committee for Ethics in Animal Experimentation under protocol number 2084/11, and it is in agreement with the guidelines of the Brazilian College for Animal Experimentation (COBEA). Twenty male three-month-old C57BL/6 mice weighing 24 ± 3 g were obtained from the “Instituto do Coração” colony (InCor, São Paulo, SP, and Brazil). The mice were housed in standard cages (3-4 mice/cage) in a temperature-controlled room (22oC ± 1), on a 12/12 h light/dark cycle with the lights on at 6:30 a.m. After one week acclimation period, the mice were implanted with electrodes and blood vessel catheters as described below. Then they were housed individually. Food and tap water were available ad libitum. C a r d i o v a sc ul ar Pha ogy: Open A c c e s s ISSN: 2329-6607