Myoplasmic [Ca2+] determines myosin phosphorylation and isometric stress in agonist-stimulated swine arterial smooth muscle.
Smooth muscle cells can regulate both their rate of stress development and the level of maintained stress. Agonist-induced steady-state stress was dependent on changes in aequorin-estimated myoplasmic [Ca2+] in the range of 120-190 nM. Higher levels of [Ca2+] were observed only transiently after stimulation and correlated with higher levels of myosin phosphorylation and faster stress development. A single regulatory system (Ca2+-dependent myosin light-chain phosphorylation) appears to control both mean crossbridge cycling rates (rate of contraction or shortening velocity) and the number of attached crossbridges (stress).
Rembold
C M
CM
Department of Medicine Cardiology, University of Virginia School of Medicine, Charlottesville 22908.
Murphy
R A
RA
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D009218:Myosins / Q000378:metabolism*; D010766:Phosphorylation; D013312:Stress, Physiological / Q000503:physiopathology; D013552:Swine
D002120:Calcium Channel Agonists; D009218:Myosins; D002118:Calcium