哺乳類骨格筋細胞における微小管の分布および配列に関する電子顕微鏡的研究

抄録

The distribution and arrangement of microtubules (MTs) in the skeletal muscle cells of rat and mouse diaphragms were examined by thin-section electron microscopy. In the central portion of the muscle cells, most of the MTs run longitudinally between the myofibrils and beneath the sarcolemma, and some MTs traverse predominantly at the level of the I-band, especially the A-I junction, showing a lattice-like arrangement. At the cell periphery, where the nuclei and Golgi apparatus are located, MTs are aggregated in the perinuclear region, from which they radiate to take a longitudinal course beneath the sarcolemma and to run in a transverse direction at the I-band level. At the ends of muscle cells, MTs are abundant running along the long axes of the processes. MTs are often found to be closely associated with the membranous organelles including mitochondria.
Quantitative analyses indicate that MTs are remarkably numerous in the peripheral zone of muscle cells as compared to the deeper and central zones. Interestingly, the MT-density was almost the same in both typical red and white muscle cells. MTs are significantly high in density at the cell ends, although the MT-density varies considerably between different cells. The results obtained from morphological and quantitative analyses are discussed with special reference to the possible involvement of MTs in the intracellular transport as well as structural support.