Chandrashekhar Y, Prahash A J, Sen S, Gupta S, Anand I S
Division of Cardiology, Veterans Affairs Medical Center and the University of Minnesota Medical School, Minneapolis 55417, USA.
J Am Coll Cardiol. 1999 Aug;34(2):594-602. doi: 10.1016/s0735-1097(99)00222-3.
This study evaluated contractile function in cardiomyocytes isolated from hearts with global left ventricular dysfunction following ischemia-reperfusion.
Ischemia followed by reperfusion is associated with transient contractile dysfunction, termed "stunning." It is not clear whether this phenomenon is primarily due to intrinsic cardiomyocyte contractile dysfunction.
Global contractile dysfunction was induced in isolated perfused rat hearts (n = 8) using a model of transient global ischemia (20 min) followed by reperfusion (20 min). Hearts perfused uninterrupted for 40 min were used as controls (n = 8). Cardiomyocytes were isolated using enzymatic digestion and were studied under varying degrees of inotropy (using increasing extracellular calcium [Ca2+]o) and loading conditions (varying extracellular perfusate viscosity). Mechanical function was studied with video edge detection and intracellular calcium ([Ca2+]i) kinetics using fura-2 AM.
Global ischemia-reperfusion increased left ventricle (LV) end diastolic pressure (450% vs. 33%, p < 0.01) and reduced LV developed pressure (9% vs. 33%, p < 0.01), LV positive (3% vs. 26%, p < 0.01) and negative (5% vs. 33%, p < 0.01) dP/dt. However, cells isolated from these hearts did not manifest contractile dysfunction. In fact, cell shortening (p < 0.0001) and peak rate of cell shortening (p < 0.05) and increase in [Ca2+]i with each contraction (p < 0.024) were higher in these cells during stimulation with [Ca2+]o of 1 to 10 mmol/liter. The EC50 values for calcium dose response and the slope of the relation between change in [Ca2+]i and change in cell length were no different between the groups. Cell loading (with increasing superfusate viscosity from 1 cp to 300 cp) also did not reveal any abnormalities in cells from the hearts subjected to ischemia-reperfusion.
Cardiomyocytes isolated from hearts with ischemia-reperfusion-induced LV dysfunction or "stunning" have normal contractile function and normal [Ca2+]i transients, when studied both in the unloaded and loaded state. Our data suggest that nonmyocyte factors such as abnormalities in extracellular matrix or abnormal myocyte-interstitial tissue coupling may be important for the genesis of cardiac contractile failure in the stunned heart.
本研究评估了从缺血再灌注后出现全心左心室功能障碍的心脏中分离出的心肌细胞的收缩功能。
缺血后再灌注与短暂的收缩功能障碍相关，称为“顿抑”。目前尚不清楚这种现象是否主要归因于心肌细胞内在的收缩功能障碍。
使用短暂全心缺血（20分钟）后再灌注（20分钟）的模型，在离体灌注大鼠心脏（n = 8）中诱导全心收缩功能障碍。持续灌注40分钟的心脏用作对照（n = 8）。使用酶消化法分离心肌细胞，并在不同程度的心肌收缩力（使用增加的细胞外钙[Ca2+]o）和负荷条件（改变细胞外灌注液粘度）下进行研究。使用视频边缘检测研究机械功能，并使用fura-2 AM研究细胞内钙（[Ca2+]i）动力学。
全心缺血再灌注增加了左心室（LV）舒张末期压力（450%对33%，p < 0.01），降低了LV的发展压力（9%对33%，p < 0.01）、LV的正（3%对26%，p < 0.01）和负（5%对33%，p < 0.01）dP/dt。然而，从这些心脏中分离出的细胞并未表现出收缩功能障碍。事实上，在用1至10 mmol/升的[Ca2+]o刺激期间，这些细胞的细胞缩短（p < 0.0001）、细胞缩短峰值速率（p < 0.05）以及每次收缩时[Ca2+]i的增加（p < 0.024）更高。两组之间钙剂量反应的EC50值以及[Ca2+]i变化与细胞长度变化之间关系的斜率没有差异。细胞负荷（随着灌注液粘度从1 cp增加到300 cp）在缺血再灌注心脏的细胞中也未显示出任何异常。
当在无负荷和有负荷状态下进行研究时，从缺血再灌注诱导的LV功能障碍或“顿抑”心脏中分离出的心肌细胞具有正常的收缩功能和正常的[Ca2+]i瞬变。我们的数据表明，非心肌细胞因素，如细胞外基质异常或心肌细胞 - 间质组织耦合异常，可能对顿抑心脏中心脏收缩功能衰竭的发生很重要。
