大鼠压力负荷性心力衰竭进展过程中三磷酸腺苷敏感性钾通道功能观察

目的 建立压力负荷性心力衰竭(心衰)大鼠模型,在模拟缺血的条件下,研究心衰发展的不同阶段大鼠左室心肌细胞膜三磷酸腺苷敏感性钾通道(K_(APT)通道)的功能变化.方法 雄性Wistar大鼠被随机分配到4周假手术组(F4)11只、12周假手术组(F12)10只、4周手术组(T4)13只和12周手术组(T12)10只.使用腹主动脉缩窄法建立大鼠心衰模型.通过右侧颈总动脉插管记录血流动力学指标.使用改良的Langendorff法分离大鼠左室心肌细胞.应用全细胞膜片钳技术,在电压钳模式下,记录F4、T4、F12、T12各组大鼠左室心肌细胞在正常状态及模拟缺血液灌流条件下K_(ATP)通道电流情况,比较0 mV电压下各组电流密度大小.结果 动脉收缩压、舒张压及平均动脉压从术后4周开始明显升高,但是到12周的时候有所降低.左心室舒张末压和左心室内压上升/下降最大速率在T4组没有明显变化,在T12组左心室舒张末压明显升高而左心室内压上升/下降最大速率明显降低.膜片钳实验结果显示,基础状态下,全细胞膜电流密度在各组之间差异均无统计学意义,但是在模拟缺血液灌流25 min时,T12组大鼠K_(ATP)通道的开放幅度比F12组明显增加,电流密度明显增大(28.11±3.91)pA/pF比(11.55±1.17)pA/pF,P<0.01],而T4组与F4组之间差异无统计学意义(14.09±5.74)pA/pF比(11.74±3.68)pA/pF,P>0.05].无论是T12组还是T4组,大鼠心肌中K(ATP)通道的基因表达并没有增多.结论 成功构建压力负荷性大鼠心衰模型,T4组心肌肥厚,T12组呈慢性心衰.心肌细胞膜K_(ATP)通道在慢性心衰期对缺血的敏感性增强,全细胞膜电流明显增大,而这种反应发生在心肌细胞K_(ATP)通道表达增多之前.

ATP-Sensitive potassium channel function during the progression of pressure overload heart failure in rats

Objective To investigate K_(ATP) channel function of cardiomyocytes isolated from the left ventricular wall of rats with or without abdominal aortic constriction at different time points under normal or simulative ischemic conditions. Methods Male Wistar rats were randomized into 4 groups ( n = 10-13 ) :4-week sham-operated group (F4), 4-week aortic-banded group (T4), 12-week sham-oporated group (F12), 12-week aortic-banded group (T12). Chronic pressure overload model was established by abdominal aortic constriction. Left ventricular myocytes were isolated by modified Langendorff porfusion method post in vivo hemodynamical measurements. The whole-cell patch-clamp technique was used to record transient outward current of K_(ATP), channel on myocytes under normal and simulative ischemic perfusion conditions. The current densities of K_(ATP), channel between F4 and T4 group, F12 and T12 group were compared under 0 mV of test potentia. Results SBP, DBP and MBP were significantly increased in T4 group compared to F4 group, but were similar between T12 and F12 groups. LVEDP and ±dp/dtmax were similar between T4 and F4 groups and LVEDP was significantly increased while ±dp/dtmax significantly reduced in T12 group than that in F12 group. Whole-cell membrane current densities were similar between F4 and T4 group or F12 and T12 group under normoxic condition, the K_(ATP) current densities increased dramatically in T12 group (28. 11±3.91 ) pA/pF vs ( 11.55±1.17 ) pA/pF, P < 0. 01 ], but not in T4 group ( 14. 09±5.74 ) pA/pF vs ( 11. 74±3.68 ) pA/pF, P >0. 05 ] in myocytes exposed to ischemic solution for 25 minutes. The total number of K_(ATP) channel in ventricular myocytes was similar between F4 and T4 group or F12 and T12 group. Conclusions The sarcolemmal K_(ATP) channel was more sensitive to ischemia and the current magnitude was significantly increased at the stage of congestive heart failure. The functional change of K_(APT) channel occurred before the increase of total number of K_(ATP) channel.