sq-23377 and fasudil

Rabbit aorta smooth muscle cells (SMC) in long-term culture retracted in less than 10 min in response to a sequential order of stimulations by concanavalin A (Con A) and fetal calf serum (FCS). With additional continuous stimulation by FCS, the SMC took on a circular shape and were anchored to the substrate by retraction fibrils. This rounding was observed only when the cells were sequentially stimulated by Con A and FCS. Depletion of intracellular Ca2+ stores by the addition of EGTA and Ca2+ ionophores inhibited the rounding. Transient phosphorylation of MLC20 was observed in the initial stage during the SMC rounding. The extent of monophosphorylated MLC20 increased for up to 5 min to a maximal value of 49%. The diphosphorylated form reached a maximal value of 29% within 2 min; then both forms of MLC20 decreased. The process of the SMC rounding was inhibited by antimycin A or cytochalasins, in a dose-dependent manner, findings which suggested a dependency on both metabolic energy and actin-containing microfilaments. The smooth-muscle-relaxing agent, HA1077, also inhibited the process of SMC rounding. These observations suggest that a cellular contractile process might be involved in rounding of SMC.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Aorta; Blood; Calcimycin; Calcium; Cells, Cultured; Chickens; Concanavalin A; Culture Media; Cytochalasin B; Cytochalasins; Diltiazem; Egtazic Acid; Gizzard, Avian; Ionomycin; Isoquinolines; Kinetics; Muscle, Smooth; Muscle, Smooth, Vascular; Myosin Subfragments; Phosphorylation; Rabbits; Verapamil