Sarcomere relaxation in hamster diaphragm muscle.
Coirault, Catherine, Denis Chemla, Isabelle Suard, Jean-Claude Pourny,
and Yves Lecarpentier.
INSERM 275-Laboratoire d'Optique Appliqu[acute]ee-ENSTA-Ecole
Polytechnique, 91120 Palaiseau; and Service d'Explorations
Fonctionnelles, H[circumflex]opital de Bic[circumflex]etre, 94275 Le
Kremlin-Bic[circumflex]etre, France
APStracts 3:0120A, 1996.
We characterized instantaneous sarcomere relaxation over the load
continuum in isolated hamster diaphragm muscles by means of laser
diffraction. In afterloaded twitches, sarcomere relaxation displayed
two consecutive phases. The bulk of sarcomere lengthening occurred
during the first phase and corresponded in time to muscle
lengthening. The second phase of sarcomere relaxation was slower and
corresponded in time to tension decay. At Lo, the peak velocity of
sarcomere lengthening (SVL) was linearly related to both the maximum
extent of sarcomere shortening ([delta]SL) and sarcomere length at
peak shortening (SLmin) (each p<0.01). Varying preload modified
the SVL versus SLmin relationship but not the SVL versus [delta]SL
relationship. At a given preload, muscle tension decay began at a
similar sarcomere length, regardless of the afterload level. In
conclusion, our results support the role played by sarcomere length
in regulating the diaphragm muscle lengthening rate but not the rate
of tension decline.
Received 18 August 1995; accepted in final form 16 February 1996.
APS Manuscript Number A910-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96