异丙基肾上腺素不同给药模式对小鼠心脏腺苷酸活化蛋白激酶活性的影响

目的:探讨β-肾上腺素受体(β-AR)激动剂异丙基肾上腺素(ISO)2种给药模式对小鼠心脏腺苷酸活化蛋白激酶(AMPK)活性的影响,以及AMPK激动剂在这2种模式中对心脏结构和功能的不同作用。方法:采用皮下植入微渗透压泵的方法给予雄性BALB/c小鼠持续14 d输注ISO(5 mg·kg~(-1)·d~(-1))以及每日皮下注射AMPK激动剂AICAR(250 mg·kg~(-1)·d~(-1))。分别于植入泵14 d后和植入泵14 d并撤泵3 d后,利用超声心动图和血流动力学方法检测心脏功能并收集心脏样本。Western blot检测AMPK的磷酸化水平。结果:持续输注ISO14 d后心脏AMPK的磷酸化水平较对照组明显增加(P0.05),AICAR并不进一步增加AMPK磷酸化水平,反而有减少ISO引起的心脏AMPK磷酸化水平增加的趋势。AICAR明显抑制ISO引起的心脏重量增加。反映心脏收缩功能的左室短轴缩短率(FS)和左心室压力最大上升速率(+dp/dt_(max))在ISO组显著高于对照组(P0.05),AICAR并不进一步增加心脏收缩功能。反映心脏舒张功能的左室舒张末压(LVEDP)在各组并无明显改变。持续输注异丙基肾上腺素14 d并撤泵3 d后心脏AMPK的磷酸化水平与对照组的差异无统计学显著性。AICAR明显抑制ISO引起的心脏重量增加。+dp/dt_(max)在ISO组明显低于对照组(P0.05),提示收缩功能下降。AICAR+ISO组与ISO组相比,有增加+dp/dt_(max)的趋势。反映心脏舒张功能的LVEDP在ISO组明显升高(P0.05),提示舒张功能明显降低。而AICAR则显著改善了ISO引起的舒张功能异常(P0.05)。给予ISO后,AMPK磷酸化水平增加和心率增加的时间曲线一致,均为5 min开始升高,30 min开始下降至基础水平。结论:β-AR持续激动使AMPK活性持续升高,而撤泵后AMPK活性则降至对照水平。观察AMPK激动对心脏功能的改善作用需避免β-AR激动引起的正性变时变力效应的干扰。

Distinct effects of different β-adrenoceptor stimulation patterns on car-diac AMP-activated protein kinase activity

AIM: To investigate the cardiac AMP-activated protein kinase (AMPK) activity and the effects of AMPK activator on cardiac structure and function in the mice with different β-adrenoceptor (β-AR) stimulation patterns. METHODS: Male BALB/c mice were subcutaneously injected with AMPK activator (AICAR, 250 mg· kg^-1·d^-1) or saline, and infused with β-AR agonist isoproterenol (ISO, 5 mg·kg^-1·d^-1) for 14 d. The cardiac functions were evaluated by echocardiography or hemodynamic method, and the hearts were harvested after infusion cessation immediately or 3 d later. Phosphorylated AMPK (p-AMPK) was measured by Western blot. RESULTS: Sustained ISO infusion increased p-AMPK level. AICAR did not further increase p-AMPK but attenuated ISO-induced increase in heart weight. Sustained ISO infusion increased cardiac systolic function as indicated by left ventricular fractional shortening (FS) and maximum rate of pressure rise (+dp/dt_max). The cardiac systolic function was not further increased by AICAR. The cardiac diastolic function as indicated by left ventricular end-diastolic pressure (LVEDP) was not different in each group. In contrast, cardiac p-AMPK level was similar between the control mice and the mice with sustained ISO infusion and ceased infusion for 3 d. In this model, AICAR improved the cardiac systolic and diastolic functions, which were impaired by ISO. Moreover, the increased pattern of p-AMPK level was similar with that of heart rate upon ISO stimulation. CONCLUSION: Sustained ISO infusion increases p-AMPK. After ISO infusion cessation for 3 d, p-AMPK is decreased to the basal level. β-AR-induced inotropic effects should be avoided to investigate the cardioprotective role of AMPK activation in the β-AR stimulation models.