Exercise Preconditioning To Exhaustion Of Rat Myocardium Exploration Of The Timeliness Of Protection

Purpose:At present,although there has been a great breakthrough in the research on the protective mechanism of exercise preconditioning heart,there is still no unified conclusion on the duration of EP cardiac protective effect after the suspension of training.Therefore,this study aims to explore the timeliness of ep-induced cardiac protective effect after the cessation of exercise training.In this study,EP was used to explore the time-effectiveness of myocardial protective effect in exhausted rats from the perspectives of myocardial enzymology,electrocardiogram,cardiac function,and mitochondrial respiratory function.In order to provide a new theoretical and experimental basis for the prevention and treatment of sports injury of soldiers and athletes.Method:1.Groups and models of experimental animals56 healthy male SPF rats,rats were randomly divided into 7 groups（n=8）:the control group（CON group）,exhaustion group group（EE）,sports preadaptation group（EP）,motor exhaustion after preconditioning group（EP+EE group）,the EP+EE groups and randomly divided into 1D,3D group,9D group,18D,reference Domenech and Lennon reclaimed study to establish animal model of EP intervals’s motion,speed of 26 m/min,movement time for 60min,slope as 5°(exercise intensity 75%VO_2max).According to the exercise for 15min and rest for 5min,three groups were repeated in the exercise process of 60min,and intermittent treadmill exercise was carried out for 3 consecutive weeks to establish EP animal model.EP+EE group performed exhaustion exercise at a speed of 30m/min on day l,3,9 and18 after stopping EP exercise for 3 weeks.The exhaustion standard was reached when the rats were continuously stuck in the back segment of the platform and the photoelectric acoustic stimulation was ineffective.2.The levels of NT-proBNP and cTnI in serum of rats were determined by ELISA.3.The electrocardiograms of rats were recorded by PowerLab data acquisition and analysis system.4.Cardiac function parameters were detected with Millar pressure volume catheter,and cardiac function parameters of rats in each group were recorded:Cardiac output（CO）,stroke volume（SV）,left ventricular end systolic volume（Ves）,left ventricular end-diastolic volume（Ved）,left ventricular end-diastolic pressure（Ped）,left ventricular end systolic pressure（Pes）,heart rate（HR）,ejection fraction（EF）,the relaxation time constant（Tau）,the maximum rate of pressure rise(dp/dt_max),the maximum rate of pressure drop(dp/dt_min),left ventricular end systolic pressure volume relationship（ESPVR）,left ventricular end-diastolic pressure volume relationship（EDPVR）index.5.Application of high resolution breathing apparatus to detect the rat myocardial mitochondria complexesⅡⅠstate 3 and 4,complex and compoundⅣRespiratory rate,and comparing the Respiratory rate Control than（Respiratory Control Ratio,RCR）.Results:1.Comparison of myocardial serum indexes in each groupCompared with the CON group,the contents of serum NT-proBNP and cTn-I in each exhaustion group were significantly increased,with statistical difference（P<0.05）.There was no statistical difference between the CON group and EP group（P>0.05）.Compared with the EE group,the contents of serum NT-proBNP and cTn-I in the 1D,3D and 9D groups were significantly reduced,with statistical differences（P<0.05）.There was no statistical difference between the 18D group and the EE group（P>0.05）.There was no statistical difference between the 1D group and the 3D group（P>0.05）.Compared with 1D group,the content of serum NT-proBNP in the 9D and 18D groups was significantly increased,with statistical difference（P<0.05）.Compared with the 9D group,the content of serum NT-proBNP in the3D group was significantly reduced,while the content of serum NT-proBNP and cTn-I in the18D group was significantly increased,showing a statistical difference（P<0.05）.2.Comparison of ecg indexes in rats in each groupCompared with the CON group,there was a statistical difference in the increase of HR and elevation of ST segment in the exhaustion group（P<0.05）,while there was no statistical difference between the CON group and the EP group（P>0.05）.Compared with the EE group,the QRS interval of 1D,3D and 9D was shorter and the degree of ST segment elevation was reduced,showing statistical difference（P<0.05）.Compared with the EE group,there was no statistical difference in HR and QRS interval between the 18D group and the EE group（P>0.05）.There was no statistical difference between the 1D group and the 3D group（P>0.05）.Compared with the 1D group,there were statistical differences between the 9D and18D groups in HR increase and ST segment elevation（P<0.05）.Compared with the 9D group,the QRS interphase of the 18D group was significantly prolonged,with a statistical difference（P<0.05）.3.Comparison of cardiac function indexes in rats in each groupCompared with the CON group,the absolute values of CO,SV,Pes,ESPVR,dp/dt_maxax and dp/dt_minin in the EP group increased,while those of the Ves group decreased,and the cardiac function of the rats was enhanced,showing a statistical difference（P<0.05）.Compared with the EE group,the reduction degree of cardiac function indicators in the 1D,3D and 9D groups was reduced,showing a statistical difference（P<0.05）.Compared with the EE group,there was no statistical difference in cardiac function indicators in the 18D group（P>0.05）.There was no statistically significant difference in cardiac function between the 1D group and the 3D group（P>0.05）.Compared with the 1D group,EDPVR and Tau values of rats in the 9D group and the 18D group were increased,and the absolute values of ESPVR,dp/dt_max and dp/dt_min were significantly decreased,and the myocardial systolic and diastolic functions were decreased,showing statistical differences（P<0.05）.Compared with the 9D group,the absolute values of dp/dt_max,dp/dt_min,ESPVR,EDPVR,Tau,and cardiac function were increased in the 3D group,with statistical differences（P<0.05）.Compared with the 9D group,SV,EF and EDPVR were significantly decreased in the 18D group,while ESPVR and Ves were increased and cardiac function was decreased in the 18D group,with statistical differences（P<0.05）.4.Comparison of respiratory rate of cardiac mitochondrial respiratory complex in rats in each groupCompared with the CON group,the respiratory rate and RCR values of myocardial mitochondrial complex I and IV state 3 in the EP group were increased,showing statistical differences（P<0.05）.Compared with the CON group,the respiratory rate and RCR values of myocardial mitochondrial complex I,II and IV state 3 in the exhaustion group decreased,especially in the EE group and the 18D group,with a statistical difference（P<0.05）.Compared with the CON group,the respiration rate of mitochondrial complex I state 4 in the EE,3D,9D and 18D groups increased,showing statistical differences（P<0.05）.Compared with the EE group,there was no statistical difference in the respiratory rate of mitochondrial complex II state 3 in the 1D,3D and 9D groups（P>0.05）,while the respiratory rate of myocardial mitochondrial complex I and IV state 3 in the 1D,3D and 9D groups was increased,showing a statistical difference（P<0.05）.Compared with the 18D group,there was no statistical difference in the respiratory rate of myocardial mitochondrial complex in EE group（P>0.05）.Compared with the 1D group,there was no statistical difference in the respiratory rate of myocardial mitochondrial complex in the 3D and 9D groups（P>0.05）.Compared with the 1D group,the respiratory rates and RCR values of complex I,II and IV state 3 and complex I state 4 in the 18D group decreased,and the respiratory rates of complex I state 4 increased,showing a statistical difference（P<0.05）.Compared with the 9D group,18D groupⅠstate 3 respiration rate and mitochondrial complex RCR value significantly reduced,statistically significant（P<0.05）,the rest of the various compounds the respiratory rate of no significant difference.5.Correlation analysis between respiratory rate of mitochondrial respiratory chain complex and cardiac function parameters in rats in each groupThrough Pearson linear correlation analysis,the respiratory rate of complex II in the CON group was strongly positively correlated with CO（P<0.01）,negatively correlated with HR（P<0.05）,and positively correlated with dp/dt_max（P<0.05）.In the EE group,the respiration rate of complex I state 4 was strongly positively correlated with EDPVR（P<0.01）and negatively correlated with dp/dt_max（P<0.05）.The respiration rate of complex I state 3 was positively correlated with CO（P<0.05）and positively correlated with EF（P<0.05）.The respiratory rate of complex II was positively correlated with Pes（P<0.05）.The respiratory rate of complex II in EP group was negatively correlated with HR value（P<0.05）.The respiratory rate of mitochondrial complex IV was strongly negatively correlated with HR value（P<0.01）.In 1D group,the respiratory rate of complex I state 3 was strongly positively correlated with CO（P<0.01）.The respiratory rate of complex IV was positively correlated with CO（P<0.05）.The respiratory rate of complex IV was positively correlated with CO in the 3D group（P<0.05）.The respiratory rate of complex I state 4 was positively correlated with Ped in the 18D group（P<0.05）.The state 3 respiratory rate of complex I was positively correlated with CO（P<0.05）.Conclusion:1.Cut myocardial mitochondrial NADH and exhaustion exercise through FNADH₂electron transport chain,reduced the mitochondrial respiratory complexⅠ,Ⅱ,Ⅳstate 3respiration rate,mitochondrial respiratory complexⅠstate 4 respiration rate increase,lead to myocardial energy metabolic disorders,reduce cardiac function.2.Movement preadaptation through increases mitochondrial NADH,electron transport chain increased mitochondrial respiratory complexⅠ,Ⅳstate 3 respiration rate,thus improving myocardial mitochondrial respiratory function,enhance the myocardial energy metabolism and enhance the cardiac function,so as to play a protective role of exhaustion rats.3.The protective effect of exercise preconditioning on the heart of exhausted rats was time-dependent and decreased with the extension of discontinuation time.The effect was the most significant within 3 days after discontinuation of training,which was weakened on the9th day and completely disappeared on the 18th day.