Sarcomere-length dependence of lattice volume and radial mass transfer of myosin cross-bridges in rat papillary muscle

Naoto Yagi, Hiroshi Okuyama, Hiroko Toyota, Junichi Araki, Juichiro Shimizu, Gentaro Iribe, Kazufumi Nakamura, Satoshi Mohri, Katsuhiko Tsujioka, Hiroyuki Suga, Fumihiko Kajiya

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


We examined the sarcomere length-dependence of the spacing of the hexagonal lattice of the myofilaments and the mass transfer of myosin cross-bridges during contraction of right ventricular papillary muscle of the rat. The lattice spacing and mass transfer were measured by using X-ray diffraction, and the sarcomere length was monitored by laser diffraction at the same time. Although the lattice spacing and the sarcomere length were inversely related, their relationship was not exactly isovolumic. The cell volume decreased by about 15% when the sarcomere length was shortened from 2.3 μm to 1.8 μm. Twitch tension increased with sarcomere length (the Frank-Starling law). At the peak tension, the ratio of the intensity of the (1,0) equatorial reflection to that of the (1,1) reflection was smaller when the tension was greater, showing that the larger tension at a longer sarcomere length accompanies a larger amount of mass transfer of cross-bridges from the thick to the thin filament. The result suggests that the Frank-Starling law is due to an increase in the number of myosin heads attached to actin, not in the average force produced by each head.

Original languageEnglish
Pages (from-to)153-160
Number of pages8
JournalPflugers Archiv European Journal of Physiology
Issue number2
Publication statusPublished - May 2004


  • Constant volume
  • Cross-bridge
  • Frank-Starling law
  • Laser diffraction
  • Sarcomere length
  • Synchrotron radiation
  • X-ray diffraction

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)


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