家兔心肌细胞肌浆网与横管系统关系的观察

JUNCTION OF SARCOPLASMIC RETICULUM WITH TRANSVERSE TUBULAR SYSTEM MEMBRANES OF RABBIT MYOCARDIAL CELLS

本文就家兔心肌细胞的连接,特别是心肌细胞内横小管与肌浆网的“特化连接”进行了研究。心肌细胞膜深入肌细胞内,形成横小管,围绕在肌丝区之间。兔心肌横小管较发达,切面呈椭圆形,直径为150nm,横靠心肌纤维Z线。心肌细胞肌浆网分支互相吻合,围绕每个肌丝区之间,网孔较大,其末端膨大,附于Z线附近的横小管上,与横小管共同构成二联管。肌浆网和横小管互不相通,相邻两膜不融合,两膜间有10nm宽的空隙,肌浆网规则地向横小管伸出足突。有些二联管中,横小管与肌浆网间存在着膜的“连接”,即横小管的一侧,有长约375nm的细胞膜增厚,电子密度加大,并且分裂成2层。相对应的肌浆网膜也产生同样的特化。横小管膜和肌浆网膜之间,有宽约31nm的间隙,间隙中央有电子致密物质,致密区和透明区有规则地间隔,构成不连续的小点。

Junctions of myocardial cell,specially the intraeellular junctions of transverse tubule system with sarcoplasmie reticulum membranes were observed and described in the present paper.The tubular invaginations of the sarcolemma constitutes the transverse tubule(T tubule)which surround the myofibril in rabbit.The transverse tubular system of cardiac muscle are well developed.The tubule has an elliptical shape in cross section and 15 nm in diameter and is constantly located at the level of Z line.The sarcoplasmic retieulum consists of a simple plexiform arrangement of tubular elements forming a loose network around the myofibrillae.Small terminal expansions of the reticulum are closely applied to the membrane of the T tubules to form Diad.The membranes of the small flattened expansions of the reticulum and T tubules are in contact with each other,but the lumina of the two elements do not communicate.There is a gap of about I0 nm between them and foot processes from the membrane of sarcoplasmic reticulum are regularly extended toward the Ttubules.In addition,intracellular membranous junctions are observed between T tubules and sarcoplasmic reticulum of Diad.Each junction with membrane area of about 375 nm long becomes thicker and divides into two layers.Between them there is a gap of 31 nm wide,in which it is filled up with electron,dense material,forming some discontinuous spots which consisted of dense and light areas arranged at regular intervals.