Responsive And Adaptive Changes Of HSP70, Free Radicals Metabolism And Na～+-K～+-ATPase Activity To Aerobic Endurance Exercise In Myocardium Of Rats

Introduction: Heat shock proteins (HSP) are also called stress proteins that undergo preferential synthesize following a variety of stressors and can protect economies or cells under stressed conditions. Exercise has been demonstrated as a physiological inducer of HSP. Recently many scientists start to research the relationships of exercise and HSP, who want to use these to prevent over-training and protect tissues after excessive exercise. It has great influence in training effect and body ability status that the changes of free radicals metabolism are induced by exercises. There are not sufficient researches about the regular changes of HSP70, free radicals metabolism and Na+-K+-ATPase activity in training course. So the aim of this study was to observe the responsive and adaptive changes of HSP70, free radicals metabolism and Na+-K+-ATPase activity in four weeks endurance training of fix quantity in myocardium of rats.Method: Three months old male Sprague-Dawley rats were randomly divided into rest control groups (CG) and training groups (TG). Rats of training groups ran for 30 min at speed of 25m/min a day, 6d/week. Before training and at the four seventh days of every training week., HSP70 content, MDA content and Na+-K+-ATPase activity in myocardium of rats were measured at pre-exercise, post-exercise immediately and 3h after exercise respectively. Results:(1) HSP70 content increased gradually after exercise, but significant change was only in WK1 and WK2 groups. In these groups, HSP70 content in 3h after exercise groups (3hE) was significant greater than in pre-exercise groups (PE) (P<0.05) and post-exercise immediately groups (AE) (P<0.01). No significant difference between PE and AE.(2) Pre-exercise HSP70 content was significant greater in WK1 group (P<0.05) than in CG, and greatest in WK2 group. It started to decrease in the third week (WK3 vs. WK2 P<0.05). No significant difference between WK4 group and CG.(3) Total antioxidant ability (T-AOC) in WK1 groups decreased immediately afterexercise (P<0.05) and continued to decrease till 3 hours after. MDA content increased after exercise immediately in WK2 groups (P<0.01), at the same time T-AOC decreased. MDA and T-AOC had no significant changes after exercise in WK3 and WK4 groups.(4) Pre-exercise MDA content had no significant changes in four weeks endurance training course. Pre-exercise T-AOC had significant increase after one week training (P<0.001), but decreased to normal level after two weeks training.(5) Na+-K+-ATPase activity raised till three hours after exercise in untrained rats. Post-exercise Na+-K+-ATPase activity decreased greatly in WK2 groups (AE vs. PE P<0.05). Na+-K+-ATPase activity had no significant changes after exercise in WK1, WK3 and WK4 groups.(6) After endurance training, Na+-K+-ATPase activity had an upward trend. Conclusion:(1) HSP70 content has an upward trend after exercise. Its change range mainly lie on stress degree that induced by exercise. It implicates the magnitude of HSP70 responsive change can reflect intensity of stimulative.(2) It makes a period of time from stress starting to HSP70 synthesizing greatly even the exercise stress had enough intensity.(3) The adaptive change of pre-exercise HSP70 content is climbing at first and start to go back after adapting the exercise training that implicates the training load must be enough great to induce HSP70 accumulating.(4) With adapting to training of fix quantity, free radical metabolism in myocardium will restore balance. But the antioxidant ability has increased and can endure greater intensity of exercise stress.(5) The responsive changes of Na+-K+-ATPase activity relate to the stress degree by exercise induced.(6) After endurance exercise, the ability of Na+, K+-pump in cardiac cell membrane has increased and the protective mechanism of heart has improved.