Key Points
- To determine the relative contributions of myosin light-chain kinase (MLCK) and protein kinase C (PKC) to basal and stimulated LC20 phosphorylation and force production in arterial smooth muscle.
- Examined intact and Triton X-100-demembranated smooth-muscle strips from rat tail arteries.
- Applied pharmacological inhibitors of MLCK (ML-9, wortmannin) and PKC (chelerythrine, calphostin C) across resting and stimulated states.
- Basal LC20 phosphorylation in intact arteries requires MLCK alone, whereas alpha1-adrenoceptor stimulation enhances phosphorylation via both MLCK and PKC pathways.
- Calcium-induced phosphorylation in demembranated muscle is mediated solely by MLCK, reflecting the loss of PKC alpha and beta isoforms during detergent permeabilization.
- LC20 phosphorylation correlates with contractile tension in intact and permeabilized tissue, with negligible Ser-19 and Thr-18 diphosphorylation observed under resting or activated conditions.
Structured PICO
PPopulationRat tail arterial smooth-muscle strips (RTA)
IInterventionMLCK inhibitors (ML-9 and wortmannin) and PKC inhibitors (chelerythrine and calphostin C)
OOutcomeLC20 phosphorylation and force developmentsurrogate
This study elucidates the distinct roles of MLCK and PKC in regulating myosin light-chain phosphorylation and contraction in arterial smooth muscle.