Contraction-induced injury to single permeabilized muscle fibers
from fast and slow muscles of the rat following single stretches.
Macpherson, Peter C. D., M. Anthony Schork, and John A. Faulkner.
Institute of Gerontology and Department of Physiology, Department
of Biostatistics, University of Michigan, Ann Arbor, Michigan 48109
-2007
APStracts 3:0169C, 1996.
Susceptibility to contraction-induced injury was investigated in
single permeabilized muscle fiber segments from fast extensor
digitorum longus and slow soleus muscles of rats. We tested the
hypotheses that following single stretches of varying strains and
under three conditions of Ca2+ activation, none, submaximum, and
maximum: (i) the magnitude of the deficit in maximum isometric force
is dependent on the work done to stretch the fiber and (ii) for each
condition of activation and strain, fast fibers incur greater force
deficits than slow fibers. When all data on force deficits were
analyzed together, the best predictors of the overall force deficits
for both fast and slow muscle fibers were linear regression models
that introduced the simultaneous but independent effects of strain
and average force, (R2 = 0.52 and R2 = 0.63 respectively). Under
comparable conditions, greater force deficits were produced in fast
than slow fibers. Despite differences in the strain required to
produce injury in fast and slow muscle fibers, for a given force
deficit the ultrastructural damage was strikingly similar.
Received 6 November 1995; accepted in final form 15 May 1996.
APS Manuscript Number C670-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96