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

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ISO 14 d后心脏AMPK的磷酸化水平较对照组明显增加（P＜0.05），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／dtmax）在ISO组显著高于对照组（P＜0.05）， 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／dtmax在ISO组明显低于对照组（P＜0.05），提示收缩功能下降。 AICAR＋ISO组与ISO组相比，有增加＋dp／dtmax的趋势。反映心脏舒张功能的LVEDP在ISO组明显升高（P＜0.05），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（P＜0.05）。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。[ ABSTRACT] 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 evalu-ated 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/dtmax).The cardiac systolic function was not further increased by AICAR .The cardiac diastolic func-tion 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-in-duced inotropic effects should be avoided to investigate the cardioprotective role of AMPK activation in the β-AR stimulation models.国家自然科学基金资助项目中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)122177-21833