Myosin light-chain phosphorylation and potentiation of dynamic function in mouse fast muscle.

The intent of this study was to determine if the stimulation-induced increase or "potentiation" of dynamic function of mouse extensor digitorum longus muscle (in vitro 25°C) during work cycles is graded to myosin regulatory light-chain (RLC) phosphorylation. To do this, concentric force and muscle work output during sinusoidal length changes were determined before (unpotentiated) and after (potentiated) the application of conditioning stimuli (CS) producing incremental elevations in RLC phosphorylation from rest. Sine wave excursion was from 1.

Potentiation of in vitro concentric work in mouse fast muscle.

Phosphorylation of myosin regulatory light chain (R-LC) is associated with potentiated work and power during twitch afterloaded contractions in mouse extensor digitorum longus muscle [R. W. Grange, C.

Increased force development rates of fatigued mouse skeletal muscle are graded to myosin light chain phosphate content.

Phosphorylation of myosin regulatory light chain (R-LC) increases the Ca2+ sensitivity of cross-bridge transitions, which determine rate of force development in skinned skeletal muscle fibers. The purpose of this study was to determine whether phosphorylation of R-LC is the molecular basis for the increased force development rates (+dF/dtmax) observed in fatigued mouse extensor digitorum longus muscle (EDL) (stimulated in vitro at 25 degrees C). Parameters of twitch and tetanic force were obtained after the application of different-frequency conditioning stimuli (CS), which were used to vary R-LC phosphorylation and reduce peak tetanic force (Po).