Abstract
The effects of the Rho-kinase inhibitor, Y-27632 [1] on Ca2+-sensitization of force induced by arachidonic acid (AA), phorbol 12,13-dibutyrate (PDBu), GTPgammaS, and by the stable thromboxane analog, 9,11-dideoxy-9alpha,11alpha-methanoepoxy-PGF2alpha (U-46619), were determined in alpha-toxin-permeabilized smooth muscles. Y-27632 relaxed (up to 99%) Ca2+-sensitization by GTPgammaS (10 microM) and U46619 (1 microM), but not by PDBu (20 microM), and reduced GTPgammaS-induced myosin light chain (MLC20) phosphorylation from 28% to 17% (P=0.002). GTPgammaS-induced force sensitization was inhibited by Y-27632 more potently when the inhibitor was added during the plateau of force than prior to stimulation. In alpha-toxin-permeabilized smooth muscle, Y-27632 inhibited AA (50 microM)-induced Ca2+-sensitization of force (by 66 +/- 1.3%) and reduced MLC20 phosphorylation. In contrast, Y-27632 did not relax force Ca2+-sensitized by AA in smooth muscle permeabilized with Triton X-100. We conclude that (i) AA induces Ca2+-sensitization through dual mechanisms, one mediated by Rho-kinase (or a related kinase), and (ii) Rho-kinase is not required for phorbol ester-induced Ca2+-sensitization.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / pharmacology
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Amides / pharmacology*
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Animals
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Arachidonic Acid / pharmacology*
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Calcium / metabolism
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Calcium / pharmacology*
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Enzyme Inhibitors / pharmacology
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Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology*
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Guanosine Triphosphate
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In Vitro Techniques
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Intracellular Signaling Peptides and Proteins
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Models, Biological
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Muscle Contraction / drug effects
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Muscle, Smooth, Vascular / drug effects
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Muscle, Smooth, Vascular / physiology*
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Myosin Light Chains / metabolism
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Octoxynol
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Permeability
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Phorbol 12,13-Dibutyrate / pharmacology*
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Phosphorylation / drug effects
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Protein Serine-Threonine Kinases / antagonists & inhibitors
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Protein Serine-Threonine Kinases / metabolism
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Pulmonary Artery
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Pyridines / pharmacology*
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Rabbits
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Type C Phospholipases
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rho-Associated Kinases
Substances
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Amides
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Enzyme Inhibitors
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Intracellular Signaling Peptides and Proteins
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Myosin Light Chains
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Pyridines
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Y 27632
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Arachidonic Acid
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Phorbol 12,13-Dibutyrate
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Guanosine 5'-O-(3-Thiotriphosphate)
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15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
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Guanosine Triphosphate
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Octoxynol
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Protein Serine-Threonine Kinases
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rho-Associated Kinases
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Type C Phospholipases
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Calcium