Nag A C, Lee M L
Department of Biological Sciences, Oakland University, Rochester, Michigan 48309-4401, USA.
Tsitologiia. 1997;39(10):907-12.
The myofibrils of adult rat cardiac muscle cells in culture break down and later reorganize into mature myofibrils. The myofibrillar breakdown and reorganization processes have been investigated with electron microscopical and immunocytochemical studies. The immunocytochemical studies included antibodies to actin, myosin, titin, and alpha-actinin. In addition, rhodamine-labeled phalloidin has been used. These studies revealed that the myofibrils were disorganized into amorphous and/or other forms during breakdown process. Some of these myofibrils undergo degradation and finally extrusion through exocytosis. The reorganization of myofibrils takes place mainly with the participation of the existing myofibrillar proteins in myocytes. This remyofibrillogenesis showed the emergence of punctate alpha-actinin from the existing amorphous alpha-actinin along with the differentiation of titin periodicities, which remained attached to the alpha-actinin structures. The punctate alpha-actinin later differentiated into periodicities, forming Z-lines. The periodicities of actin were differentiated from the amorphous actin and associated with the Z-lines, giving rise to titin, alpha-actinin, and actin complexes. Later, myosin filaments became associated with these complexes, forming sarcomeres where other myofibrillar proteins participated in the formation of mature myofibrils. The temporal sequence of differentiation of periodicities of certain myofibrillar proteins varied among different myocytes and within a single myocyte. The dynamic role of adult cardiac myocytes in the reconstruction of myofibrils is a remarkable phenomenon, which stabilizes adult cardiac muscle cells in long-term culture.
培养的成年大鼠心肌细胞的肌原纤维会分解，随后重新组织形成成熟的肌原纤维。已通过电子显微镜和免疫细胞化学研究对肌原纤维的分解和重组过程进行了调查。免疫细胞化学研究包括使用针对肌动蛋白、肌球蛋白、肌联蛋白和α-辅肌动蛋白的抗体。此外，还使用了罗丹明标记的鬼笔环肽。这些研究表明，在分解过程中，肌原纤维会解体为无定形和/或其他形式。其中一些肌原纤维会发生降解，最终通过胞吐作用排出。肌原纤维的重组主要是在心肌细胞中现有肌原纤维蛋白的参与下进行的。这种再肌原纤维生成表现为从现有的无定形α-辅肌动蛋白中出现点状α-辅肌动蛋白，同时肌联蛋白周期性发生分化，并与α-辅肌动蛋白结构保持相连。点状α-辅肌动蛋白随后分化为周期性结构，形成Z线。肌动蛋白的周期性结构从无定形肌动蛋白中分化出来，并与Z线相关联，形成肌联蛋白、α-辅肌动蛋白和肌动蛋白复合物。随后，肌球蛋白丝与这些复合物结合，形成肌节，其他肌原纤维蛋白参与成熟肌原纤维的形成。某些肌原纤维蛋白周期性分化的时间顺序在不同的心肌细胞之间以及单个心肌细胞内有所不同。成年心肌细胞在肌原纤维重建中的动态作用是一个显著的现象，它使成年心肌细胞在长期培养中保持稳定。
