肥大心肌细胞的闰盘变化

Alteration of Intercalated Disc in the Hypertrophied Myocardium

目的:闰盘是心肌细胞特殊的复合连接装置。已有报道在某些心脏疾患中闰盘间隙扩张。作者在以前的研究工作中发现,肥大心肌细胞自体吞噬活跃,细胞降解产物(残余体)排入扩张T管,但从T管如何排出细胞尚不大清楚。本实验目的是观察残余体排出通道以及T管和闰盘的关系。方法:利用胞嘧啶单核苷酸酶作为溶酶体标志物,在电镜下观察大鼠腹主动脉缩窄4周(n=4)及10周(n=6)的左心室肥大心肌细胞的残余体排泄过程。假手术大鼠(n=5)作为对照组。结果:本文发现在缩窄10周组心肌细胞闰盘间隙增宽,并和附近扩张T管相连通。在T管、闰盘间隙中及细胞外间质中有膜样物质存在。用细胞化学胞嘧啶单核苷酸酶方法证实了这些物质为溶酶体的降解物。结论:残余体可能从胞质排入T管,再到闰盘间隙。此结果提示在心肌肥大过程中,心肌细胞发生适应性改变,闰盘间隙可能成为残余体排泄的通道。

Objective: Intercalated discs (ID) of the myocardium represent complex pattern of specialized cell junctions. Widening of the intercellular space at ID has been reported in certain heart diseases. Our previous work showed that the autophagic activity was high and the degraded cellular elements (residues) were expelled into the dilated T-tubules in the hypertrophied myocardium of rats. But how to expel the residues from T-tubules remains obscure. The purpose of the present study was to investigate the passage of residues and the relation to T-tubules and ID. Methods: Using cytidine monophosphatase(CMPase) as a marker of lysosome under EM, the expelling of residues of hypertrophied myocardium induced by abdominal aortic stenosis in rats for 4 weeks (n=4) and 10 weeks(n=6) was studied. Sham-operated rats (n=5)were used as controls. Results: At 10 weeks after stenosis, discontinuous widening of the intercellular spaces at ID and the space connected with adjacent dilated T-tubules were observed. There were membrane fragments in the T-tubules,the space of ID and extracellular interstitial substance. Those fragments were proved to be lysosomal degraded elements by CMPase method. The above changes were not found in controls and at 4 weeks after stenosis. Conclusion: The residues are expelled from the cytoplasm into the T-tubules,then into the space of ID, and finally discharged. It is suggested that the hypertrophied process the myocardium undergoes adapted changes,in which the intercellular space of ID might serve as a passage of expelling the residues.