Exercise‐induced electrical remodeling of endocardial and epicardial tissue in perfused rat hearts

Abstract

Exercise‐training (ET) prolongs the epicardial monophasic action potential (MAP) of female rats at rest but changes at higher heart rates (HR), and gender differences are unknown. To assess this, female and male Sprague‐Dawley rats were randomly assigned to either voluntary wheel running (TRN) or control group (SED). After six weeks, rats were anesthetized, hearts excised, and cannulated on a Langendorff apparatus. MAP's were recorded using 0.25 mm chlorided silver wires from base and apex, areas representative of ENDO and EPI tissue, respectively. The sinoatrial node was stimulated at frequencies from 200 to 400 BPM. Initial spike duration (SD) and total action potential duration (APD) were measured. SED males and females had comparable SD and APD at all HR except 400 BPM, where ENDO APD was shorter in females (p<0.05). The SD and APD were unaltered by ET in males, while in females the ENDO APD at 350 and 400 BPM was significantly shortened (p<0.05). Further, TRN females showed a prolonged EPI SD at 400 BPM (p<0.05). Results suggest that the cardiac electrical remodeling seen with exercise training is gender‐specific and dependent on HR. Supported by Marquette University Way Klinger Fellowship.