Time Course of Cardiac Function and Oxidative Stress Induced by an Acute Bout of Exercise

Abstract

Research indicates that a single, strenuous bout of exercise in previously sedentary individuals results in the production of free radicals and impaired calcium handling that persists for up to three days following the exercise bout. These alterations may negatively impact cardiac function, by compromising both systolic and diastolic function. PURPOSE: The purpose of this study was to examine the effects of an acute bout of exercise on cardiac function immediately, 24-hours, 48-hours, and 72-hours following the exercise bout. A secondary purpose was to delineate possible mechanisms to explain these alterations in cardiac function. METHODS: Forty male Sprague-Dawley rats completed an acute bout of exercise on a motorized treadmill at a speed of 25 m/min and a 5% grade for 60 minutes. Upon completion of the exercise bout, rats were randomized into four groups and were sacrificed immediately (IMM), 24-hours (24h), 48-hours (48h), and 72-hours (72h) after the acute bout. A fifth group consisted of rats who did not perform the exercise bout, which served as controls (CON, n= 10). At the scheduled time of sacrifice, hearts were isolated and perfused by the Langendorf method for determination of ex vivo cardiac function. Left ventricular sections were obtained from each heart and examined for lipid peroxidation indices (MDA). RESULTS: In the CON group, left ventricular developed pressure (LVDP), dP/dtmax, and dP/dtmin values were 78±4 mmHg, 3586±260 mmHg/sec, and −2500±195 mmHg/ sec, respectively. After the acute bout of exercise, cardiac function progressively declined during the first 48 hours. Forty-eight hours after the exercise bout, LVDP decreased from control levels by 41 %, dP/dtmax declined by 60%, and dP/dtmin experienced a 39% decrease (p < 0.05). At 72 hours post, cardiac function had returned to within control levels. Lipid peroxidation demonstrated a similar trend. MDA progressively increased from 386+67 pmol/mg protein prior to exercise, up to 530+63 pmol/mg protein 24 hours post-exercise. As was the case with cardiac function, baseline levels of MDA returned to control levels by 72 hours post-exercise. CONCLUSION: These data indicate that a single, strenuous bout of exercise performed by previously sedentary rats may impair cardiac function for up to 48 hours following the bout. This decrement to cardiac function is associated with increases in lipid peroxidation.