骨格筋単一筋原線維の直径変化: AFMによる計測

抄録

In the present studies, the diameter of single skeletal myofibrils was measured under various physiological conditions by AFM. Our AFM instrument is not suitable for precise diameter measurements of specimen having the diameter range of micrometer like single myofibrils. Therefore, we modified our AFM system by incorporating precise piezo systems so as to be useful for the present purpose. Single myofibrils were prepared by homogenizing glycerinated muscle fibers of the rabbit psoas muscle. Myofibrils were fixed on the surface of cover slip coated with aminosilanes. A small glass sphere was adhered to the tip of AFM cantilever to smoothly touch to the surface of myofibrils. The piezo stage could be moved in the horizontal and the vertical directions in the range of 10 μm with the accuracy of ± 2 nm. The diameter of myofibrils was determined by comparing the distance moved for the glass sphere fixed to AFM cantilever to touch the top surface of myofibrils and that to touch the surface of the cover slip. The error of the diameter measurements was < ± 5 nm. The diameter of single myofibrils thus obtained was 1.119 ± 0.042 μm (n=5) in the relaxed state and 1.026 ± 0.039 μm (n=5) in the rigor state. Thus the diameter of myofibrils in the rigor state was smaller by 8% than that in the relaxed state. We also further examined the diameter of single myofibrils under other physiological states. The results thus obtained will be compared with the data for the lattice spacing of actomyosin filaments of muscle fibers reported by X-ray diffraction studies. [J Physiol Sci. 2006;56 Suppl:S79]