ラット骨格筋線維の活動性肥大に関する電子顕微鏡的研究

抄録

The present study was carried out to examine the structural changes of the skeletal muscle fibers induced by exercise at the electron microscopic level. Twelve male albino rats were examined, of which six were used for the training group and the remainings were as controls. After training for ten weeks, the rats were sacrificed and their M. tibialis anterior was prepared for the examination with a light and electron microscope. The results obtained were summarized as follows :
1) The muscular training caused the hypertrophy of muscle fibers, the rate of which was about 20 percent in their cross section.
2) After training, the number of myofibrils per unit area of fiber cross section decreased. There were correlations between the fiber diameter and the number of myofibrils. Thus these relations can be expressed by a different regression equation for each group ; that is, Y = 50.17X -1391.47 for trained group and Y=53.89X -1182.91 for control group, respectively. (X: fiber diameter in micron, Y : number of myofibrils)
3) No significant difference existed between the trained and the control rats in the relative volumes of fiber components.
4) There were no significant differences between the trained and the control rats in respect to the myofilamental parameters, such as myosin filament concentration, distance between myosin filaments, myosin filament diameter, actin filament diameter and ratio of actin to myosin filament.
From the present study, it may be concluded that the hypertrophy of muscle fibers induced by exercise is attributed not to the increase in the number of myofibrils, but to the relative increase of both the size of each myofibril and the sarcoplasmic volume.