Changes of Expression of Stretch-activated Potassium Channel TREK-1 mRNA and Protein in Hypertrophic Myocardium

The expression of stretch activated potassium channel TREK-1 mRNA and protein of hypertrophic myocardium was measured. Using a model of hypertrophy induced by coarctation of abdominal aorta in male Wistar rats, the expression of TREK-1 mRNA and protein was detected by using semi quantitative RT-PCR and Western blot respectively. At 4th and 8th week after constriction of the abdominal aorta , rats developed significant left ventricular hypertrophy. As compared to sham-operated group, stretch-activated potassium channel TREK-1 mRNA was strongly expressed and protein was up regulated in operation groups （P〈0.05）. It was concluded that the expression of TREK-1 was up-regulated in hypertrophic myocardium induced by chronic pressure overload in Wistar rats.

Speckle Tracking Echocardiography Assessment of Global and Regional Contraction Dysfunction in the Mice Model of Pressure Overload

Speckle tracking echocardiography（STE） has been applied to the evaluation of cardiac contraction dysfunction. However, there were few studies on alteration of global and regional STE parameters in the process of myocardial hypertrophy and heart failure. In this study, STE was applied to evaluate the global and regional cardiac function under heart failure and hypertrophy in the mice model of pressure overload. Adult mice were subjected to mild or severe aortic banding with a 25 Gauge（G） or 27 G needle. After surgery, STE and conventional echocardiography were used in the sham group（n=10）, mild trans-aortic banding（TAB） group（n=14） and severe TAB group（n=10） for 8 weeks. The results showed that the mice subjected to severe TAB showed a significant change in fractional shortening（FS）, left ventricular（LV） mass, and left ventricular end diastolic diameter（LVEDD）（P〈0.05 for each）. Meanwhile, there were no significant differences in FS and LVEDD between the sham group and mild TAB group during the experimental procedures（P〉0.05 for both）. STE analysis revealed that longitudinal strain（LS） was significantly decreased in the severe TAB group as compared with the sham and mild TAB groups（P〈0.05 for both） from the postoperative week 1. LS in the mild TAB group was reduced as compared to the sham group（P〈0.05）. Radial strain（RS） and circumferential strain（CS） were significantly decreased in the severe TAB group as compared to the sham group and the mild TAB group（P〈0.05 for both） from the postoperative week 1（P〈0.05 for both）. Compared to the sham group, CS in the mild TAB group maintained unchanged during the test period, and RS was reduced only on the postoperative week 6（P〈0.05）. Finally, regional contraction dysfunction was analyzed in both hypertrophic and failing myocardium in longitudinal and radial directions. It was found that LS was largest in the apex region and RS was smallest in the apex region in the healthy and hypertrophic myocardium. It was also found that compared to the sham group, only base longitudinal strain in the mild TAB group was decreased. Each of regional strain in the severe TAB group was uniformly depressed in radial and longitudinal directions. It is concluded that STE has provided a non-invasive and highly feasible way to explore the global and regional contraction dysfunction in hypertrophic and heart failure myocardium in the murine model of pressure overload.