| Objective: Exhaustive exercise causes myocardial damage and increases the incidence of arrhythmia,exercise preconditioning can enhance the ability of myocardium to resist ischemia and hypoxia,thereby producing a protective effect on the heart and reducing the incidence of arrhythmia.Therefore,by constructing an exhaustive exercise model and exercise preconditioning model,this study compares the effects of exercise preconditioning on sodium current,NaV1.5 gating effect and related regulatory proteins,and explores the possible mechanism of exercise preconditioning to reduce the occurrence of arrhythmia.Methods: Healthy male SD rats were taken as the research object,and they were randomly divided into 4 groups,namely the control group(Ctrl),exhaustion group(EE),exercise preconditioning group(EP),exercise preconditioning and exhaustion group(EP+EE).Among them,the rats in the EP group and EP+EE group performed intermittent swimming for 3 weeks with a tail weight of 3%,the rats in the Ctrl group and the EE group were fed routinely for 3weeks.After 3 weeks,the rats in the EE group and EP+EE group performed a one-time exhaustive swimming exercise with a weight of 3%.After the model was prepared,the electrocardiogram of each group of rats was recorded,the serum CK-MB and c Tn I concentration of each group were detected by ELISA,the sodium channel current of rat ventricular myocytes was recorded by patch clamp technique,and the NaV1.5 gating effect was analyzed.Western blot was used to detect the expression levels of HIF-1α,SIRT1 and sodium channel protein NaV1.5 in ventricular muscle tissue of rats in each group.Results:1.Comparing the general conditions of the rats,the Ctrl group has smooth and shiny fur,its appearance is serene,the eyes are piercing,and the weight increases spontaneously.The EP group is similar to the Ctrl group in general,but the weight gain is slower.After each exercise pre-adaptation,congestion around the eyes will appear,which disappears after swimming.2.Compared with the Ctrl group,the serum CK-MB and c Tn-I concentrations in the EP+EE group and the EE group increased significantly(P<0.05).Compared with the EE group,the serum CK-MB and c Tn-I concentrations of the EP+EE group and the EP group showed a decreasing trend(P<0.05).Compared with the EP group,the concentrations of CK-MB and c Tn-I in the EP+EE group showed a significant increase(P<0.05),and the difference was statistically significant.3.Observe the changes in the electrocardiogram of rats in each group at the overall level of the animal.Compared with the Ctrl group,the QRS interval of rats in the EP+EE group was prolonged,the PR interval was prolonged,and ST segment elevation(P<0.05,).Compared with the Ctrl group,the QRS interval of the EE group was prolonged(22.23±0.86 vs 15.78±0.65)and the PR interval was prolonged(56.53±0.95 vs 40.57±1.27),ST segment elevation(0.045±0.007 vs 0.022±0.006,P<0.05,).Compared with the EE group,the QRS interval of rats in the EP+EE group was shortened(19.82±1.87 vs 22.23±0.86),PR interval shortened(52.49±1.82 vs 56.53±0.95),ST segment decreased(0.036±0.003 vs 0.045±0.007,P<0.05).Compared with Ctrl group,the QRS interval in the EP group was prolonged,and the PR interval was prolonged(P<0.05).4.Record the action potential and sodium current changes of rat ventricular myocytes at the cellular level.The whole-cell patch clamp technique was used to detect the difference in sodium channel gating characteristics such as action potential,sodium current,steady-state inactivation curve and intermediate state inactivation curve of rat ventricular myocytes.Compared with the Ctrl group,the action potential 0 phase rise of the EE group rat myocardial cell action potential slowed down and the 2nd and 3rd phase repolarization prolonged,the parameters such as the rising amplitude and the maximum ascent rate of the EP+EE group were significantly different from those of the EE group(P <0.05).Compared with the Ctrl group,the sodium current amplitude and the sodium current density of the EE group were significantly reduced.Compared with the EE group,the peak current of the EP+EE group recovered,and the difference was statistically significant(P<0.05).The steady-state inactivation curve of sodium channels in the EE group shifted significantly to the left compared with the Ctrl group(P<0.05),indicating that the sodium current change is related to the steady-state inactivation process and mainly depends on the inactivation voltage.That is,sodium ion channels are more likely to be inactivated during exhaustive exercise,resulting in a decrease in open channels and a decrease in sodium current.Compared with the EP+EE group,the EP group had a significant difference in left-shift relief(P<0.05).The current closed state and the intermediate inactivation time constant(τ)of each group were significantly different,the EE group was shorter than the Ctrl group(P<0.05),and the EP group was compared with the EP+EE group,and the τ value was restored(P<0.05).Compared with the Ctrl group,the recovery curve of the EE group shifted to the right after inactivation,and the recovery time constant was prolonged(P<0.05).Compared with the EP+EE group,the recovery time constant was recovered in the EP group(P<0.05).5.Detect the difference in the expression levels of HIF-1α,SIRT1 and sodium channel protein NaV1.5 at the molecular level.Western blot was used to detect the differences in the total expression and membrane expression of HIF-1α,SIRT1 and sodium channel protein NaV1.5,and further infer the differences in the distribution of sodium channel protein NaV1.5.Compared with the Ctrl group,the expression of HIF-1α in the myocardial tissue of the EP group and the EE group was significantly increased,and the expression level of SIRT1decreased(P<0.05).Compared with the EE group,the expression of HIF-1α in the EP+EE group was significantly reduced,and the expression level of SIRT1 was increased(P<0.05).Compared with the EP group,the expression of HIF-1α in the EP+EE group was significantly increased,and the expression level of SIRT1 was significantly decreased(P<0.05).Compared with the Ctrl group,the expression of NaV1.5 membrane protein in the rat cardiomyocytes of the EP group and the EE group was significantly decreased(P<0.05).Compared with the EE group,the NaV1.5 membrane protein expression in the EP+EE group was significantly increased(P<0.05).Compared with the EP group,the expression of NaV1.5 membrane protein in the EP+EE group was significantly reduced(P<0.05).Conclusion:1.Exercise preconditioning reduces the occurrence of arrhythmia and reduces the damage to ventricular muscle tissue caused by exhaustive exercise by increasing the sodium current of ventricular myocytes and shortening the duration of action potentials.2.Exercise preconditioning affects the gating characteristics of NaV1.5,leading to an increase in sodium current in ventricular myocytes.3.Exercise preconditioning increases the expression of NaV1.5 cell membrane by positively regulating SIRT1.4.Exercise preconditioning reduces the damage to ventricular muscles of rats by exhaustive exercise by regulating the expression of HIF-1α. |
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