Induction of molecular and mechanical transformations in canine skeletal muscle by chronic neuromuscular stimulation

• Published in: Journal of muscle research and cell motility 1997-02, Vol.18 (1), p.81-90
• Main Authors: Zhang, K M, Wright, L D, Hu, P, Spratt, J A, Wechsler, A S, Briggs, F N
• Format: Article
• Language: English
• Subjects: Animals; Calcium; Calcium - metabolism; Calcium-Transporting ATPases - metabolism; Dogs; Electric Stimulation; Fluorescein-5-isothiocyanate - metabolism; Heart; Muscle Fibers, Fast-Twitch - metabolism; Muscle Fibers, Fast-Twitch - physiology; Muscle Fibers, Slow-Twitch - metabolism; Muscle Fibers, Slow-Twitch - physiology; Muscle, Skeletal - metabolism; Muscle, Skeletal - physiology; Myosin Heavy Chains - metabolism; Neuromuscular Junction - physiology; Organ Size; Phenotype; Space life sciences
• ISSN: 0142-4319; 1573-2657
• DOI: 10.1023/A:1018685001214

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.