Load dependency in force-length relations in isolated single cardiomyocytes

Gentaro Iribe, Toshiyuki Kaneko, Yohei Yamaguchi, Keiji Naruse

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)

Abstract

The previously reported pressure-volume (PV) relationship in frog hearts shows that end-systolic PV relation (ESPVR) is load dependent, whereas ESPVR in canine hearts is load independent. To study intrinsic cardiac mechanics in detail, it is desirable to study mechanics in a single isolated cardiomyocyte that is free from interstitial connective tissue. Previous single cell mechanics studies used a pair of carbon fibers (CF) attached to the upper surface of opposite cell ends to stretch cells. These studies showed that end-systolic force-length (FL) relation (ESFLR) is load independent. However, the range of applicable mechanical load using the conventional technique is limited because of weak cell-CF attachment. Therefore, the behavior of ESFLR in single cells under physiologically possible conditions of greater load is not yet well known. To cover wider loading range, we contrived a new method to hold cell-ends more firmly using two pairs of CF attached to both upper and bottom surfaces of cells. The new method allowed stretching cells to 2.2μm or more in end-diastolic sarcomere length. ESFLR virtually behaves in a load independent manner only with end-diastolic sarcomere length less than 1.95μm. It exhibited clear load dependency with higher preload, especially with low afterload conditions. Instantaneous cellular elastance curves showed that decreasing afterload enhanced relaxation and slowed time to peak elastance, as previously reported. A simulation study of a mathematical model with detailed description of thin filament activation suggested that velocity dependent thin filament inactivation is crucial for the observed load dependent behaviors and previously reported afterload dependent change in Ca2+ transient shape.

Original languageEnglish
Pages (from-to)103-114
Number of pages12
JournalProgress in Biophysics and Molecular Biology
Volume115
Issue number2-3
DOIs
Publication statusPublished - Aug 1 2014

Keywords

  • Cell mechanics
  • Mechano-electric coupling
  • Modeling
  • Shortening deactivation

ASJC Scopus subject areas

  • Biophysics
  • Molecular Biology

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