Synergist muscle ablation and recovery from nerve-repair grafting: contractile and metabolic function.
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/cm(2)) 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.
Larkin
L M
LM
Division of Geriatric Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109, USA. llarkin@umich.edu
Kuzon
W M
WM
Halter
J B
JB
D000818:Animals; D003714:Denervation; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000378:metabolism; D006614:Hindlimb; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009119:Muscle Contraction / Q000502:physiology*; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000294:innervation* / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D011916:Rats, Inbred F344; D013537:Sutures; D013710:Tendons / Q000502:physiology; D013979:Tibial Nerve / Q000502:physiology* / Q000601:surgery*
D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D006003:Glycogen