AJP - Cell Physiology, Vol 258, Issue 3 C436-C442, Copyright © 1990 by American Physiological Society
Contraction-induced injury: recovery of skeletal muscles in young and old mice
S. V. Brooks and J. A. Faulkner
Department of Physiology, University of Michigan, Ann Arbor 48109-0622.
We tested the hypothesis that after the same amount of contraction-induced
injury, skeletal muscles in old mice regenerate less well than muscles in
young mice. Extensor digitorum longus (EDL) muscles in young and old mice
were exposed to 15 min of lengthening contractions. The amount of injury
was evaluated at 3, 7, 14, 28, and 60 days by measurements of maximum
isometric tetanic force (Po) and number of fibers per cross section. When
values 3 days after lengthening contractions were expressed as a percentage
of control values, the Po (approximately 34%) and fiber number
(approximately 80%) for muscles in old mice were not different from those
in young mice, suggesting that muscles in old and young mice were injured
to the same degree. By 28 days, injured muscles in young mice regained
control values for Po and fiber number. In contrast, at 28 days, injured
muscles in old mice recovered approximately 84 and approximately 87% of
control values for Po and fiber number, respectively, and deficits in Po
persisted at 60 days. We conclude that injured muscles regenerate less well
in old mice than in young mice.
