Tansey Erin E, Kwaku Kevin F, Hammer Peter E, Cowan Douglas B, Federman Micheline, Levitsky Sidney, McCully James D
Division of Cardiothoracic Surgery, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02115, USA.
Ann Thorac Surg. 2006 Oct;82(4):1472-9. doi: 10.1016/j.athoracsur.2006.04.061.
Previous studies have demonstrated that alterations in myocardial structure, consistent with tissue and sarcomere disruption as well as myofibril dissociation, occur after myocardial ischemia and reperfusion. In this study we determine the onset of these structural changes and their contribution to electrical conduction.
Langendorff perfused rabbit hearts (n = 47) were subjected to 0, 5, 10, 15, 20, 25, and 30 minutes global ischemia, followed by 120 minutes reperfusion. Hemodynamics were recorded and tissue samples were collected for histochemical and immunohistochemical studies. Orthogonal epicardial conduction velocities were measured, with temperature controlled, in a separate group of 10 hearts subjected to 0 or 30 minutes of global ischemia, followed by 120 minutes of reperfusion.
Histochemical and quantitative light microscopy spatial analysis showed significantly increased longitudinal and transverse interfibrillar separation after 15 minutes or more of ischemia (p < 0.05 versus control). Confocal immunohistochemistry and Western blot analysis demonstrated significant reductions (p < .05 versus control) of the intercellular adherens junction protein, N-cadherin, and the active phosphorylated isoform of the principal gap junction protein, connexin 43 at more than 15 minutes of ischemia. Cellular redistribution of connexin 43 was also evidenced on immunohistochemistry. No change in integrin-beta1, an extracellular matrix attachment protein, or in epicardial conduction velocity anisotropy was observed.
These data indicate that there are significant alterations in the structural integrity of the myocardium as well as gap and adherens junction protein expression with increasing global ischemia time. The changes occur coincident with previously observed significant decreases in postischemic functional recovery, but are not associated with altered expression of matrix binding proteins or electrical anisotropic conduction.
先前的研究表明，心肌缺血再灌注后会出现心肌结构改变，这与组织和肌节破坏以及肌原纤维解离一致。在本研究中，我们确定这些结构变化的起始时间及其对电传导的影响。
对47只采用Langendorff灌注的兔心脏进行0、5、10、15、20、25和30分钟的全心缺血，随后进行120分钟的再灌注。记录血流动力学参数，并采集组织样本进行组织化学和免疫组织化学研究。在另一组10只心脏中，在温度控制下测量正交心外膜传导速度，这些心脏分别经历0或30分钟的全心缺血，随后进行120分钟的再灌注。
组织化学和定量光学显微镜空间分析显示，缺血15分钟或更长时间后，纵向和横向肌原纤维间分离显著增加（与对照组相比，p < 0.05）。共聚焦免疫组织化学和蛋白质印迹分析表明，缺血超过15分钟时，细胞间黏附连接蛋白N-钙黏蛋白以及主要缝隙连接蛋白连接蛋白43的活性磷酸化异构体显著减少（与对照组相比，p < 0.05）。免疫组织化学也证实了连接蛋白43的细胞重新分布。未观察到细胞外基质附着蛋白整合素β1或心外膜传导速度各向异性的变化。
这些数据表明，随着全心缺血时间的增加，心肌结构完整性以及缝隙连接和黏附连接蛋白表达存在显著改变。这些变化与先前观察到的缺血后功能恢复显著降低同时发生，但与基质结合蛋白表达改变或电各向异性传导无关。
