Myofilament lattice spacing as a function of sarcomere length in isolated rat myocardium

Thomas C. Irving, John Konhilas, Darold Perry, Robert Fischetti, Pieter P. De Tombe

Research output: Contribution to journalArticlepeer-review

125 Scopus citations


The Frank-Starling relationship of the heart has, as its molecular basis, an increase in the activation of myofibrils by calcium as the sarcomere length increases. It has been suggested that this phenomenon may be due to myofilaments moving closer together at longer lengths, thereby enhancing the probability of favorable actomyosin interaction, resulting in increased calcium sensitivity. Accordingly, we have developed an apparatus so as to obtain accurate measurements of myocardial interfilament spacing (by synchrotron X-ray diffraction) as a function of sarcomere length (by video microscopy) over the working range of the heart, using skinned as well as intact rat trabeculas as model systems. In both these systems, lattice spacing decreased significantly as sarcomere length was increased. Furthermore, lattice spacing in the intact muscle was significantly smaller than that in the skinned muscle at all sarcomere lengths studied. These observations are consistent with the hypothesis that lattice spacing underlies length-dependent activation in the myocardium.

Original languageEnglish (US)
Pages (from-to)H2568-H2573
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number5 48-5
StatePublished - 2000


  • Length-dependent activation
  • Trabeculas
  • X-ray diffraction

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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