Pflügers Archiv

, Volume 449, Issue 5, pp 449–457

Titin-based modulation of active tension and interfilament lattice spacing in skinned rat cardiac muscle

  • Norio Fukuda
  • Yiming Wu
  • Gerrie Farman
  • Thomas C. Irving
  • Henk Granzier
Cardiovascular System

DOI: 10.1007/s00424-004-1354-6

Cite this article as:
Fukuda, N., Wu, Y., Farman, G. et al. Pflugers Arch - Eur J Physiol (2005) 449: 449. doi:10.1007/s00424-004-1354-6

Abstract

The effect of titin-based passive tension on Ca2+ sensitivity of active tension and interfilament lattice spacing was studied in skinned rat ventricular trabeculae by measuring the sarcomere length (SL)-dependent change in Ca2+ sensitivity and performing small angle X-ray diffraction studies. To vary passive tension, preparations were treated with trypsin at a low concentration (0.31 μg/ml) for a short period (13 min) at 20°C, that resulted in ~40% degradation of the I-band region of titin, with a minimal effect on A-band titin. We found that the effect of trypsin on titin-based passive tension was significantly more pronounced immediately after stretch than at steady state, 30 min after stretch (i.e., trypsin has a greater effect on viscosity than on elasticity of passive cardiac muscle). Ca2+ sensitivity was decreased by trypsin treatment at SL 2.25 μm, but not at SL 1.9 μm, resulting in marked attenuation of the SL-dependent increase in Ca2+ sensitivity. The SL-dependent change in Ca2+ sensitivity was significantly correlated with titin-based passive tension. Small-angle X-ray diffraction experiments revealed that the lattice spacing expands after trypsin treatment, especially at SL 2.25 μm, providing an inverse linear relationship between the lattice spacing and Ca2+ sensitivity. These results support the view that titin-based passive tension promotes actomyosin interaction and that the mechanism includes interfilament lattice spacing modulation.

Keywords

Calcium sensitivityMyocardiumSarcomere lengthX-ray diffraction

Copyright information

© Springer-Verlag  2004

Authors and Affiliations

  • Norio Fukuda
    • 1
  • Yiming Wu
    • 1
  • Gerrie Farman
    • 2
  • Thomas C. Irving
    • 2
  • Henk Granzier
    • 1
  1. 1.Department of Veterinary and Comparative Anatomy, Pharmacology and PhysiologyWashington State UniversityPullmanUSA
  2. 2.Department of Biological, Chemical and Physical SciencesIllinois Institute of TechnologyChicagoUSA
  3. 3.Department of Physiology IIThe Jikei University School of MedicineTokyo 105-8461Japan