Sv. Brooks, RAPID RECOVERY FOLLOWING CONTRACTION-INDUCED INJURY TO IN-SITU SKELETAL-MUSCLES IN MDX MICE, Journal of muscle research and cell motility, 19(2), 1998, pp. 179-187
The muscles of mdx mice lack the subsarcolemmal protein dystrophin, an
d as a consequence may be more susceptible to damage induced by contra
ctions. The purpose of this study was to characterize the response of
muscles in mdx mice to contraction-induced injury in The hypothesis te
sted was that following a protocol of repeated stretches of maximally
situ. activated muscles, the magnitude of the injury is greater for mu
scles in mdx mice than for muscles in C57BL/10 control mice, and conse
quently, the muscles in mdx mice recover more slowly. Each stretch was
of 20% strain relative to muscle fibre length (L-f) at 0.5 L-f s(-1)
and was initiated from the force plateau of an isometric contraction.
The protocol consisted of a total of ten contractions, with one contra
ction occurring every ten seconds. The time-course of injury and recov
ery was determined through measurements of in situ force production at
10, 30, 45 and 60 minutes, and either 12, 24, 48 or 72 hours after th
e contraction protocol. The initial injury, as assessed by the decreas
e in force production both immediately and 60 minutes after the contra
ction protocol, was significantly greater for the muscles in mdx mice
compared with those in control mice. Over the next three days, a value
for maximum isometric force of similar to 80% of the pre-injury value
was maintained for muscles in control mice, whereas within three days
muscles in mdx mice showed complete recovery of force. For muscles in
mice, the mdx greater decrease in force during the contraction protoc
ol and the more rapid recovery indicates an increased susceptibility t
o contraction-induced injury but an enhanced rate of recovery. (C) Cha
pman & Hall Ltd.