title: Force and myosin light chain phosphorylation in dog airway smooth muscle activated in different ways.
abstract: To assess activation mechanisms of dog trachealis muscle and test whether isometric force generation could be separated from myosin light-chain (MLC) phosphorylation, force and phosphorylation were measured in the presence of wortmannin (a light-chain kinase inhibitor) or Y-27632 (a rho-kinase inhibitor) during electrically stimulated tetani and sustained contractures induced by acetylcholine, KCl, or calyculin A, a light-chain phosphatase inhibitor which caused irreversible contractures and both di- and mono-phosphorylation of light chain. Phosphorylation was not much more than half under any circumstances. A nearly constant proportionality between steady force and phosphorylation existed over a 9-fold force range during contractures and 25-sec tetani, except that force correlated best with the di-phosphorylated light chain produced by calyculin A. Phosphorylation was disproportionately higher than force at the outset of tetani, and this disproportion was exaggerated by Y-27632. The results suggest that about half the light chain is sequestered from kinases and that mechanical activation is tightly linked to phosphorylation, except at the outset of stimulation.
mesh_terms: D000109:Acetylcholine; D000577:Amides / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology*; D008387:Marine Toxins; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D018994:Myosin Light Chains / Q000378:metabolism*; D010080:Oxazoles; D010766:Phosphorylation / Q000187:drug effects; D011189:Potassium Chloride; D011725:Pyridines / Q000494:pharmacology; D013746:Tetany / Q000139:chemically induced; D014132:Trachea / Q000187:drug effects / Q000502:physiology*; D000077191:Wortmannin
chemical_list: D000577:Amides; D000730:Androstadienes; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D018994:Myosin Light Chains; D010080:Oxazoles; D011725:Pyridines; C108830:Y 27632; D011189:Potassium Chloride; C059041:calyculin A; D000109:Acetylcholine; D000077191:Wortmannin