Saetersdal T, Larsen T, Rotevatn S, Dalen H, Scheie P
Department of Anatomy, University of Bergen, Norway.
Histochemistry. 1992 Sep;98(2):73-80. doi: 10.1007/BF00716997.
The distribution of two non-collagenous glycoproteins of high molecular weight, fibronectin (FN) and laminin (LMN), was investigated in myocardial cells from the ventricle of rats, and from biopsies collected from the auricle of patients undergoing a coronary bypass operation. In order to elucidate the expression of FN and LMN across cells, non-invasive serial sectioning has been carried out by laser scanning confocal microscopy of frozen, immunostained tissue sections. In addition, immunoelectron microscopy was used to study the distribution of these antigens at higher magnifications. These studies show that FN is part of the basement membrane of the surface sarcolemma of both ventricular and atrial cells, in addition to being an abundant protein of the extracellular matrix (ECM). Along transverse tubular(TT)-membranes, FN was only detected in tubules exceeding 200 nm in diameter. Even here, the intensity of labelling varied greatly and was generally low. By contrast, a heavy investment of LMN was organized in the basal lamina along the surface sarcolemma and along ramifications of the entire TT-system in ventricular heart muscle cells. In this way, the network of TT-membrane systems of working heart muscle cells provides a supply of LMN to all depths of the myocardial fibre. In human atrial muscle cells, a regular TT-system appears to be absent. Instead occasional, deep sarcolemmal invaginations occur with diameters of 300-500 nm, the surfaces of which are also invested with LMN. The significance of the present findings has been discussed, with special reference to LMN as a possible component of a series of proteins involved in transmembrane communication between the ECM and the sarcoplasm.
研究了大鼠心室心肌细胞以及接受冠状动脉搭桥手术患者心房活检组织中两种高分子量非胶原蛋白糖蛋白，即纤连蛋白（FN）和层粘连蛋白（LMN）的分布情况。为了阐明FN和LMN在细胞间的表达情况，通过对冷冻免疫染色组织切片进行激光扫描共聚焦显微镜检查，进行了非侵入性连续切片。此外，还利用免疫电子显微镜在更高放大倍数下研究了这些抗原的分布。这些研究表明，FN不仅是细胞外基质（ECM）中的一种丰富蛋白质，还是心室和心房细胞表面肌膜基底膜的一部分。在横管（TT）膜上，仅在直径超过200nm的小管中检测到FN。即便如此，标记强度变化很大，且通常较低。相比之下，在心室心肌细胞中，LMN大量分布于沿表面肌膜的基膜以及整个TT系统的分支上。这样一来，工作心肌细胞的TT膜系统网络为心肌纤维的各个深度提供了LMN。在人类心房肌细胞中，似乎不存在规则的TT系统。取而代之的是偶尔出现的、直径为300 - 500nm的深肌膜内陷，其表面也有LMN分布。本文讨论了这些发现的意义，特别提及LMN作为参与ECM与肌浆之间跨膜通讯的一系列蛋白质的可能组成部分。
