(-)-Blebbistatin

(-)-Blebbistatin is a selective inhibitor of the ATPase activity of non-muscle myosin II^[1][2]. IC50 & Target:IC50: 0.5 to 5 μM (myosin II)^[1] In Vitro: Blebbistatin potently inhibits several striated muscle myosins as well as vertebrate nonmuscle myosin IIA and IIB with IC₅₀ values ranging from 0.5 to 5 μM. Smooth muscle myosin is only poorly inhibited (IC₅₀=80 μM)^[1]. Blebbistatin does not compete with nucleotide binding to the skeletal muscle myosin subfragment-1. The inhibitor preferentially binds to the ATPase intermediate with ADP and phosphate bound at the active site, and it slows down phosphate release. It blocks the myosin heads in a products complex with low actin affinity^[2]. In culture-activated hepatic stellate cells, blebbistatin is found to change both cell morphology and function. Stellate cells become smaller, acquire a dendritic morphology and have less myosin IIA-containing stress fibres and vinculin-containing focal adhesions. Blebbistatin impairs silicone wrinkle formation, reduces collagen gel contraction and blocks endothelin-1-induced intracellular Ca²⁺ release. It promotes wound-induced cell migration^[3]. In Vivo: Blebbistatin dose-dependently and completely relax both KCl- and carbachol-induced rat detrusor and endothelin-1-induced human bladder contraction. Pre-incubation with 10 μM blebbistatin attenuates carbachol responsiveness by 65% while blocking electrical field stimulation-induced bladder contraction reaching 50% inhibition at 32 Hz^[4].