抄録
Skinned fibers of rabbit psoas, soleus and cardiac muscles were treated with gelsolin to remove thin filament from sarcomere. Successful removal was confirmed by x-ray diffraction and SDS-page. X-ray diffraction patterns were obtained at BL-45XU of SPring8. Even at low ionic strength of 0.083, the spacing of the thick filament lattice after the removal was almost the same as that of intact lattice in the presence of MgATP. This indicated that the weak interaction between actin and myosin heads little affected thick filament lattice. To evaluate the dynamic stability of the lattice, transient changes in the x-ray diffraction patterns following the elongation of sarcomere were analyzed. Despite of the stepwise sarcomere elongation and the following exponential relaxation of instantaneous passive tension elevation, the lattice spacing gradually reduced to a steady value with a time constant of several minutes. If compressing force of the lattice is assumed to originate from Y-shaped elastic connectin/titin filament, the balancing repulsive force should instantaneously increase with the sarcomere elongation and followed by significant slow relaxation. Such slow relaxation implies viscous rearrangement of macromolecules, which naturally involves redistribution of myowater filling the lattice space. Taking the myowater state into account, the source of force establishing the lattice will be discussed. [J Physiol Sci. 2007;57 Suppl:S66]
