抄録
The intensity curve of (1,0) equatorial diffraction examined by x-ray diffraction (BL45XU at SPring-8) was subtracted by the background function and fitted by Gaussian equation. Then (1,0) peak position (d10) and the standard deviation (σ10) were calculated. The lattice spacing disorder (ε10) was evaluated as the ratio of σ10 and d10 (σ10/ d10). Experimentally the ε10 varied with both muscle length and developed force. To examine the length dependence of the ε10, x-ray diffraction image was obtained every 20 msec during isometric contraction in rat papillary muscle. When the isometric force was developed, ε10 increased in proportion to the amount of force development. Taking account of the internal shortening during the isometric contraction, it can contribute to the ε10. Actually at shorter length the ε10 at rest was slightly increased. At this length the resting tension was small, which appeared the small tension on filaments. The smaller tension on filaments can cause the filaments out of order, which may lead the increased ε10. On the contrary the amount of change in ε10 was smaller during isometric contraction at shorter length. The developed tension became also smaller, which may affect the smaller change of ε10. Therefore it is suggested that the ε10 can be affected by both the longitudinal tension on filaments and the developed tension. [J Physiol Sci. 2008;58 Suppl:S81]
