Vol. 89, Issue 4, 1469-1476, October 2000
Synergist muscle ablation and recovery from nerve-repair
grafting: contractile and metabolic function
Lisa M.
Larkin1,
William
M.
Kuzon Jr.2,3, and
Jeffrey B.
Halter1,3,4
1 Division of Geriatric Medicine, Department of Internal
Medicine, 2 Department of Surgery, and 3 Institute of
Gerontology, University of Michigan, and 4 Geriatric Research,
Education, and Clinical Center, Department of Veterans Affairs
Medical Center, Ann Arbor, Michigan 48109
After nerve-repair grafting
of medial gastrocnemius muscle, there is incomplete recovery of
specific force and sustainable power, perhaps due to overcompensation
by synergistic muscles. We hypothesized that increased workload due to
synergist ablation would enhance graft recovery. Contractile and
metabolic properties of control and nerve-repair grafted muscles, with
and without synergist ablation, were determined after 120 days
recovery. Specific force (N/cm2) and normalized power
(W/kg) were less in the experimental groups compared with controls.
Sustained power (W/kg) in the synergist-ablated nerve-repair grafted
muscle was higher than nerve-repair grafted muscle, returning to
control values. GLUT-4 protein was higher and glycogen content
was diminished in both synergist-ablated groups. In summary, synergist
ablation did not enhance the recovery of specific force or normalized
power, but sustained power did recover, suggesting that metabolic and
not mechanical parameters were responsible for this recovery. The
enhanced endurance after synergist ablation was accompanied by
increased GLUT-4 protein, suggesting a role for increased uptake of
circulating glucose during contraction.
force; sustained power; reinnervation
