Combined Transgenic Inhibition Of CaMK?and I_k1 On Cardiac Protecting

Objective This study establishes an experimental mouse model of combined transgenic inhibition of both Ca2+/calmodulin-dependent kinase ??Ca MK ?? and inward rectifier potassium current(I_k1), and observes whether the specific inhibition of both Ca MK? and(I_k1) can bring about any effects on cardiac structure and function.Methods1. AC3–I mice hybridized with Kir2.1-AAA mice and wild-type mice respectively.Extracted DNA of the offspring mice were detected by PCR. Mice were divided into 4 groups: wild type?WT?, Ca MK ? inhibited?AC3-I?, I_k1 inhibited?Kir2.1-AAA?, and combined inhibition of both Ca MK ? and I_k1?AC3-I+Kir2.1-AAA?. In each group, n=6, age and weight matched mice?8-12 weeks old and 18-25 grams? were used for all of the experiments.2. In the condition of basic state and isoproterenol?ISO? injection, mice in each group recceived surface ECG check. Measured parameters included PR interval,QRS interval, QT interval, and cardiac arrhythmia recording.3. Langendorff isolated heart perfusion technology was applied on the experiment.Four groups of mice were subjected to the experiment of halothane induced arrhythmia, ischemia-reperfusion and ischemia reperfusion with ischemia preconditioning?IP?. Then the dose of halothane induced arrhythmia was recorded.Left ventricular developed pressure, the maximum contractility and lusitropy before and after ischemia reperfusion of each mice were also recorded.4. Mice suffered cardiac hypertrophy were induced by transverse aorta constriction?TAC?. Mice were divided into 8 groups: four sham groups and four groups mice underlying transverse aorta constriction. After 2 weeks, heart weight/body weight?HW/BW? and heart weight/tibial length?HW/TL? were measured. Cardiac function parameters?LVEF, LVFS, LVEDD, etc? were measured by transthoracic echocardiography.Results1. Surface electrocardiogram?ECG? monitoring indicatd the following results: QRS interval and QT interval in AC3-I group was shorter than that in other groups in basic state and isoproterenol injection?P>0.05?. There were no significant differences of indicators of ECG and arrhythmia among four groups?P>0.05?.2. The Langendorff isolated heart perfusion experiment of halothane induced arrhythmia indicated the following results: In basic condition, the dose of halothane induced ventricular tachycardia in AAA group was larger than other groups?P<0.01?, and the dose of halothane in combined inhibition group was larger than WT group?P<0.05?. However, in the condition of diastolic heart dysfunction, the dose of halothane induced ventricular tachycardia in combined inhibition group was larger than other groups?P<0.05?, there were no significant differences of halothane among WT, AAA and AC3-I groups?P>0.05?.3. The Langendorff isolated heart perfusion experiment of ischemia reperfusion indicated the following results: In basic condition, there were no significant differences of LVDP, +dp/dtmax and-dp/dtmax among four groups?P>0.05?. In the ischemia reperfusion with IP experiment, there were no significant differences of the three indicators among four groups?P>0.05?. However, in the ischemia reperfusion without IP experiment, the three indicators in AAA group, AC3-I group and combined inhibition group recovered more better than in WT group?P<0.05?, there were no significant differences of LVDP, +dp/dtmax and-dp/dtmax among these three groups?P>0.05?.4. Two weeks after TAC, echocardiography indicated there were no significant difference compared with the sham groups?P>0.05? in cardiac systolic function parameters?LVEF, LVFS?, but there were statistical difference in diastolic parameters?LVEDd, LVEDs, LVAWd, LVAWs, LVPWd??P<0.05?. There were no significant difference of all echocardiographic indicators in four groups of TAC?P>0.05?. Two weeks after TAC, compared with sham groups, HW/BW ratio and HW/TL ratio increased significantly in TAC groups?P<0.05?. There were no significant difference of HW/BW ratio in four groups of TAC?P>0.05?. However,HW/TL ratio in AC3-I group and combined inhibition group was lower than in WT group?P<0.01?, HW/TL ratio of AAA group was lower than in WT group?P<0.05?.Conclusion Combined transgenic myocardial Ca MK? and I_k1 inhibition can eliminate the up-regulation of I_k1 in Ca MK ? inhibited mice, and improve the anti-arrhythmic effects. In addition, the combined inhibition retained the advantageous effects of resisting myocardial hypertrophy and damage. Thus, combined transgenic myocardial Ca MK? and I_k1 inhibition can protect the cardiac function better.