Muscle cytoskeletal disruption occurs within the first 15 minutes
of cyclic eccentric contraction.
Lieber, Richard L., Lars-Eric Thornell, and Jan Frid[acute]en.
Departments of Orthopaedics and Bioengineering, Biomedical Sciences
Graduate Group, University of California and Veterans, Administration
Medical Centers, San Diego, CA USA, Department of Anatomy, University
of Ume[angstrom]a, Sweden, Department of Orthopaedics,
G[diaeresis]oteborg University, Sweden
APStracts 2:0388A, 1995.
The time-course of loss of the 55,000 dalton intermediate filament
protein desmin was measured in rabbit muscles subjected to cyclic
eccentric contraction. Rabbit extensor digitorum longus (EDL) and
tibialis anterior (TA) muscles were examined 5 minutes or 15 minutes
after eccentric exercise and 1 hour or 1 day after 30 minutes of an
eccentric exercise protocol (n= 16 rabbits). The earliest change
noted was a significant loss of desmin labeling in 2.5+/-0.63% of the
rabbit extensor digitorum longus muscle (EDL) muscle fibers
(p<0.005) five minutes after initiation of eccentric exercise.
Some loss of tibialis anterior (TA) fiber desmin was also apparent at
this time period (0.24+/-.19%), but the magnitude was not
significantly different from zero (p>0.2). Fifteen minutes after
initiation of exercise, desmin loss was more pronounced, increasing
to 7.4+/-1.4% and 4.6+/-1.0% in the EDL and TA, respectively
(p<0.005). Finally, one day after 30 minutes of eccentric
exercise the percentage of fibers without desmin staining rose to
23.4+/-3.7% and 7.7+/-2.4% in the EDL and TA, respectively
(p<0.001). Loss of desmin staining occurred in the absence of
contractile or metabolic protein disruption. Increased staining
intensity of the intrasarcomeric cytoskeletal protein titin and an
inability to exclude plasma fibronectin was also observed in most but
not all fibers which had lost desmin staining. Desmin disruption thus
represents a very early structural manifestation of muscle injury
during eccentric contraction. Cytoskeletal disruption may predispose
the contractile apparatus to previously reported structural damage.
Received 27 December 1994; accepted in final form 28 August 1995.
APS Manuscript Number A1342-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.