Electrophysiological Characterization of Left Ventricular Myocytes from Obese Sprague-Dawley Rat

• Published in: Obesity (Silver Spring, Md.) Md.), 2006-05, Vol.14 (5), p.778-786
• Main Authors: Ricci, Estelle, Smallwood, Sébastien, Chouabe, Christophe, Mertani, Hichem C, Raccurt, Mireille, Morel, Gérard, Bonvallet, Robert
• Format: Article
• Language: English
• Subjects: Adipose Tissue, White; Adiposity - drug effects; animal models; Animals; Body Weight - physiology; Cardiac arrhythmia; cardiac ionic currents; cell membranes; Cell Size; Diet; diet‐induced obesity; Electrophysiology; enzyme-linked immunosorbent assay; Enzymes; gene expression; gene expression regulation; heart ventricle; Heart Ventricles - metabolism; Heart Ventricles - pathology; Heart Ventricles - physiopathology; hormone receptors; Hypertension; hypertrophy; ion channels; ion transport; Laboratory animals; leptin; Leptin - pharmacology; leptin receptors; Male; Membrane Potentials - drug effects; Membrane Potentials - physiology; myocytes; Myocytes, Cardiac - cytology; Myocytes, Cardiac - drug effects; Myocytes, Cardiac - physiology; Obesity; Obesity - metabolism; Obesity - pathology; Obesity - physiopathology; Organ Size - drug effects; Potassium; Rats; Rats, Sprague-Dawley; Receptors, Cell Surface - metabolism; Receptors, Leptin; Research methodology
• ISSN: 1071-7323; 1930-7381; 1550-8528; 1930-739X
• DOI: 10.1038/oby.2006.90

OBJECTIVE: Obesity is a complex multifactorial disease that is often associated with cardiac arrhythmias. Various animal models have been used extensively to study the effects of obesity on physiological functions, but, to our knowledge, no study related to ionic membrane currents has been performed on isolated cardiac myocytes. Therefore, we examined the electrophysiological characteristics of four ionic currents from isolated left ventricular myocytes of a high-energy (HE)-induced obesity rat model. RESEARCH METHODS AND PROCEDURES: Male Sprague-Dawley rats were fed with either a control diet or a diet containing 33% kcal as fat (HE) for 14 weeks starting at 6 weeks of age. Voltage-clamp experiments were performed on ventricular myocytes. Leptin receptor (ObR) expression was measured using ObR enzyme-linked immunosorbent assay. RESULTS: In the HE group, rats designated as obese did not develop a cardiac hypertrophy, either at the organ level or at the cellular level. Densities and kinetics of the L-type calcium current, the transient outward potassium current, the delayed rectifier potassium current, and the sodium-calcium exchange current (INCX) were not significantly different between control and obese rats. A down-regulation of ObR expression was evidenced in the heart of obese rats compared with controls. Acute exposure (5 minutes) of leptin (100 nM) did not induce a significant modification in the current densities either in control or in obese rats, except for INCX density measured in control rats. DISCUSSION: The absence of effect of leptin on INCX in obese rats could be a potential arrhythmogenic substrate in obesity.