Induction of molecular and mechanical transformations in canine skeletal muscle by chronic neuromuscular stimulation.
The canine latissimus dorsi was stimulated at 1 Hz via the thoracodorsal nerve for 70 days. Seven days of muscle stimulation caused muscle mass, fibre cross-sectional areas, and tetanic tensions to decrease. Fourteen days of stimulation produced marked decreases in Ca(2+)-uptake rates in a membrane fraction containing sarcoplasmic reticulum. At this time there was a decline in fusion frequency, but no statistically significant changes in time-to-peak tension, total contraction times, or half-relaxation times. With 42 days of stimulation a switch from the fast-twitch to the slow-twitch phenotype was indicated by elevations in the levels of expression of the slow-twitch isoforms of sarco(endo)plasmic reticulum Ca(2+)-ATPase and myosin heavy chain-I, and increases in half-relaxation times, total contraction times and time-to-peak tensions. Decreases in muscle shortening velocity correlated negatively with increases in myosin heavy chain-I levels. Up-regulation of the slow-twitch isoforms of sarco(endo)plasmic reticulum Ca(2+)-ATPase increases in half-relaxation times. The changes in the slow-twitch isoform of sarco(endo)plasmic reticulum Ca(2+)-ATPase and myosin heavy chain-I levels indicated coordinate expression of these two proteins in chronically stimulated muscles.
Zhang
K M
KM
Department of Physiology, Medical College of Virginia/Virginia Commonwealth University, Richmond 23928, USA.
Wright
L D
LD
Hu
P
P
Spratt
J A
JA
Wechsler
A S
AS
Briggs
F N
FN
D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D004285:Dogs; D004558:Electric Stimulation; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D009469:Neuromuscular Junction / Q000502:physiology*; D009929:Organ Size; D010641:Phenotype
D018995:Myosin Heavy Chains; D000252:Calcium-Transporting ATPases; D016650:Fluorescein-5-isothiocyanate; D002118:Calcium