Concanavalin A- and fetal-calf-serum-induced rounding and myosin light chain phosphorylation in cultured smooth muscle cells.
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.
Sasaki
Y
Y
Biochemical Research Laboratory, Asahi Chemical Industry, Co., Ltd., Nobeoka, Japan.
Iwata
K
K
Sasaki
Y
Y
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives*; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D001769:Blood; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D002645:Chickens; D003208:Concanavalin A / Q000494:pharmacology*; D003470:Culture Media; D003571:Cytochalasin B / Q000494:pharmacology; D003572:Cytochalasins / Q000494:pharmacology; D004110:Diltiazem / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D005895:Gizzard, Avian; D015759:Ionomycin / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D007700:Kinetics; D009130:Muscle, Smooth; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D015879:Myosin Subfragments / Q000378:metabolism*; D010766:Phosphorylation; D011817:Rabbits; D014700:Verapamil / Q000494:pharmacology
D003470:Culture Media; D003572:Cytochalasins; D007546:Isoquinolines; D015879:Myosin Subfragments; D003208:Concanavalin A; C007215:cytochalasin E; D000001:Calcimycin; D003571:Cytochalasin B; D004533:Egtazic Acid; D015759:Ionomycin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D014700:Verapamil; D004110:Diltiazem; C049347:fasudil; D002118:Calcium