Effects Of Different Intensities Of Exhaustive Exercises On Cardiac Muscle Apoptosis In Rats

Aim: Most previous studies have proven that apoptosis existed in a broad range of physiological and pathological conditions, such as heart growth, disease and exercise, however, nowadays the mechanism of this phenomenon is not very clear yet. In order to seek how. exercise-induced myocardial apoptosis work, this study investigated apoptosis occurred in cardiac muscle, as well as the roles of free radical and calcium uptaken by mitochondria after different intensities of exhaustive exercises.Methods: Thirty male adult Sprague-Dawley rats were randomly divided into three groups: control(n=10), moderate intensity exhaustive exercise(ME, n=10) and high intensity exhaustive exercise(HE, n=10). ME and HE groups, i.e. exercise groups, ran at a speed of 19.3 m?min^-1(about 76% VO_2max) and 26.8 m?min^-1 (about 92.3%VO_2max)each on the treadmill till exhaustion. The control group and exercise groups were killed by decapitation respectively at rest and immediately after exhaustive exercises, whereat 3 milliliters of blood taken from cervix were used as serum preparation. In addition, the cardiac muscle tissues were removed to make into paraffin wax and electron microscope samples, tissue and mitochondria homogenates. Then SOD activity and MDA content in serum, tissue homogenate and mitochondrial Ca²⁺ content were examined. Apoptotic myocardial nuclei were detected with microscope after Paraffin wax sections being labeled by TUNEL, while myocardial nuclei and mitochondrion ultrastructure changes were examined under electron microscope. Results:(1) Fewer TUNEL positive in the cardiac muscle was observed in the control group. Whereas myocardial apoptosis index in HE group was significantly different from that in the control group (p<0.05). The number of myocardial apoptosis in ME group...