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Biophys. J. BioFAST: First Published February 9, 2007. doi:10.1529/biophysj.107.104257
© 2007 by the Biophysical Society.

A more recent version of this article appeared on May 1, 2007.
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BIOPHYSICAL LETTERS

Interfilament Spacing is Preserved during Sarcomere Length Isometric Contractions in Rat Cardiac Trabeculae

Gerrie P. Farman 1, Edward J. Allen 1, David Gore 2, Thomas C. Irving 2 and Pieter P. de Tombe 3*

1 University of Illinois @ Chicago
2 Illinois Institute of Technology
3 University of Illinois at Chicago

* To whom correspondence should be addressed. E-mail: pdetombe{at}uic.edu.

Submitted on January 12, 2007
Revised on January 24, 2007
Accepted on 25 January 2007


  Abstract
It is generally assumed that the myofilament lattice in intact (i.e. non-skinned) striated muscle obeys constant volume. However, whether such is the case during the myocardial contraction is unknown. Accordingly, we measured inter-filament spacing by x-ray diffraction in ultra-thin isolated rat right ventricular trabeculae during a short 10 ms shuttered exposure either just prior to electrical stimulation (diastole), or at the peak of the contraction (systole); sarcomere length (SL) was held constant throughout the contraction using an iterative feedback control system. SL was thus varied in a series of SL clamped contractions; the relationship between SL and inter-filament spacing was not different between diastole and systole within 1%; this was true also over a wide range of inotropic states induced by varied [Ca2+]o. We conclude that the cardiac myofilament lattice maintains constant volume, and thus constant interfilament spacing, during contraction.

Key Words: Calcium, Length Dependency, Myocardium, Regulation, X-ray Diffraction, crossbridge




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Copyright © 2007 by the Biophysical Society.