Instantaneous force-velocity-length relationship in diaphragmatic
sarcomere.
Coirault, Catherine, Denis Chemla, Jean-Claude Pourny, Francine
Lambert, Yves Lecarpentier.
INSERM 451-Laboratoire d'Optique Appliqu_e-Ecole Polytechnique,
91125 Palaiseau Cedex and Service d'Explorations Fonctionnelles,
Centre Hospitalier et Universitaire de Bic_tre, 94275 Le Kremlin
-Bic_tre, France
APStracts 3:0478A, 1996.
The simultaneous analysis of muscle force, length, velocity and time
has been shown to precisely characterize the mechanical performance
of isolated striated muscle. We tested the hypothesis that the three
-dimensional force-velocity-length relationship, reflects mechanical
properties of sarcomeres. In hamster diaphragm strips, instantaneous
sarcomere length (SL) and muscle length were simultaneously measured
during afterloaded twitches. SL was measured by means of laser
diffraction. We also studied the influence of initial sarcomere
length, abrupt changes in total load, and 2 x 10-7 M dantrolene.
Baseline resting SL at the apex of the length-active tension curve
was 2.2 +/- 0.1 [mu]m, while SL at peak shortening was 1.6 +/- 0.1
[mu]m in the preloaded twitch and 2.1 +/- 0.1 [mu]m in the
"isometric" twitch. Over the whole load continuum and at
any given level of isotonic load, there was a unique relationship
between instantaneous sarcomere velocity (SV) and instantaneous SL.
Part of this relationship was time- and initial SL-independent and
was markedly down-shifted after dantrolene. When five different
muscle regions were considered, there was no significant variations
of SL and sarcomere kinetics along the muscle. These results indicate
that the time- and initial length-independent part of the
instantaneous force-velocity-length relationship previously described
in muscle strips reflects intrinsic sarcomere mechanical properties.
Received 9 May 1996; accepted in final form 1 October 1996.
APS Manuscript Number A444-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996