Key Points
- To elucidate the mechanisms by which cytochalasin D induces relaxation in smooth muscle tissues.
- Measured contractile responses and cytosolic Ca2+ concentrations in isolated rat aorta stimulated by high K+, noradrenaline (10 nM–1 µM), or 12-deoxyphorbol 13-isobutylate (1 µM) in Ca2+-free conditions.
- Assessed Ca2+-dependent and Ca2+-independent contractions in permeabilized chicken gizzard smooth muscle, alongside actomyosin superprecipitation velocity, MLC phosphorylation, and Mg2+-ATPase activity.
- Cytochalasin D inhibited contractions induced by high K+, noradrenaline, and DPB without altering cytosolic Ca2+ levels in rat aorta.
- In permeabilized chicken gizzard, cytochalasin D suppressed both Ca2+-induced contraction and thiophosphorylated Ca2+-independent contraction.
- Cytochalasin D decreased actomyosin superprecipitation velocity without affecting myosin light chain phosphorylation levels or Mg2+-ATPase activity.
Structured PICO
PPopulationRat aorta and chicken gizzard smooth muscles
IInterventionCytochalasin D
OOutcomeSmooth muscle contractionsurrogate
Cytochalasin D inhibits smooth muscle contraction by directly uncoupling force generation from activated actomyosin Mg2+-ATPase, without altering calcium levels or MLC phosphorylation.