Abstract:
ABSTRACT
The myosm regulatory light chain (RLC) of type II fibres is
phosphorylated by Ca2+ -calmodulin dependent myosin light chain kinase
(skMLCK) during muscular activation. The purpose of this study was to explore
the effect of skMLCK gene ablation on the fatigability of mouse skeletal muscles
during repetitive stimulation. The absence of myosin RLC phosphorylation in
skMLCK knockout muscles attenuated contractile performance without a
significant metabolic cost. Twitch force was potentiated to a greater extent in
wildtype muscles until peak force had diminished to ~60% of baseline (37.2 ±
0.05% vs. 14.3 ± 0.02%). Despite no difference in peak force (Po) and shortening
velocity (Vo), rate of force development (+dP/dt) and shortening-induced
deactivation (SID) were almost two-fold greater in WT muscles. The present
results demonstrate that myosin RLC phosphorylation may improve contractile
performance during fatigue; providing a contractile advantage to working muscles
and protecting against progressive fatigue.
