Effect of exercise training on oxidative stress and mitochondrial function in rat heart and gastrocnemius muscle

Objective: This study aimed to explore the effect of endurance training on oxidative parameters and mitochondrial function in gastrocnemius and heart muscle. Methods: Male Wistar rats were trained by running for 6 weeks. In vitro measurements of the rates of hydroxyl radical ((OH)-O-center dot) production, oxygen consumption (in either the absence, basal rate (V-0), or the presence, maximal rate (V-max), of adenosine diphosphate), and adenosine triphosphate (ATP) production were made simultaneously in permeabilized fibers. The mitochondrial function was explored after exposure or non-exposure to an in vitro generator system of reactive oxygen species (ROS). Results: V-max was not affected by training, but V0 decreased. In conditions of maximal mitochondrial functioning, an increase in ATP rate and a decrease in (OH)-O-center dot production occurred simultaneously. In vitro ROS exposure disturbed mitochondrial function, but training modified the vulnerability of V-max and ATP rate to ROS in different ways. Discussion: We hypothesize that the part of V-max devoted to proton leakage was decreased in trained rats, consequently improving ATP synthesis. The data suggest that, after training, there is more efficient use of electrons in respiratory chain energy production, rather than a greater ROS scavenging capacity.