Pflügers Archiv

, Volume 449, Issue 5, pp 449–457

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

Authors

    • Department of Veterinary and Comparative Anatomy, Pharmacology and PhysiologyWashington State University
  • Yiming Wu
    • Department of Veterinary and Comparative Anatomy, Pharmacology and PhysiologyWashington State University
  • Gerrie Farman
    • Department of Biological, Chemical and Physical SciencesIllinois Institute of Technology
  • Thomas C. Irving
    • Department of Biological, Chemical and Physical SciencesIllinois Institute of Technology
  • Henk Granzier
    • Department of Veterinary and Comparative Anatomy, Pharmacology and PhysiologyWashington State University
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