Journal of Applied Physiology, Vol 69, Issue 2 451-455, Copyright © 1990 by American Physiological Society
Prior running reduces hypertrophic growth of skeletal muscle grafts
K. A. Esser and T. P. White
Department of Kinesiology, University of Michigan, Ann Arbor 48109-2214.
Run training can increase the mass of soleus muscle grafts, yet values
remain lower than nongrafted muscle even with continued training. Thus we
tested the hypothesis that nerve-implant soleus grafts of rats previously
run trained would be refractory to the hypertrophic stimulus of ablation of
synergistic muscle. We also compared the magnitude of growth of the
nerve-implant soleus graft after ablation with that reported by others for
the nerve-intact soleus graft. We studied eight groups that differed
relative to the combination and order of treatments (running and ablation
of synergistic muscle) and the graft age at the time of the ablation
operation and study. Graft mass, protein concentration, and histochemical
fiber composition were measured. Compared with grafts from cage-sedentary
rats, the mass and protein content of the nerve-implant soleus grafts were
higher (16-63%) at all times after ablation. When the ablation operation
was performed at 56 days postgrafting, there was a 33% increase in protein
content of the soleus graft by 84 days for cage-sedentary animals. This
increase was twofold greater (P less than or equal to 0.02) than the 15%
increase that followed ablation for the grafts from the animals that had
been run trained before the ablation operation. Four weeks of run training
before the ablation operation impaired the adaptive response of muscle
grafts to the ablation of synergistic muscles, which may reflect
alterations in motor unit recruitment and/or satellite cell activity.
Ablation of synergistic muscles resulted in an absolute growth of the
nerve-implant soleus grafts that was comparable with that reported for
nerve-intact soleus grafts.
