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rdf:type | |
lifeskim:mentions | |
pubmed:dateCreated |
1990-5-25
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pubmed:abstractText |
1. Flash photolysis of caged compounds of phenylephrine, inositol 1, 4, 5 trisphosphate (InsP3), GTP gamma S, ATP, and CTP has been successfully used to study excitation-contraction coupling, contractile regulation, and contraction in smooth muscle. Major processes explored with this method were (a) the delay between agonist-receptor interaction and contraction and between the rise in InsP3, Ca2+ release and contraction; (b) the effect of myosin light chain phosphorylation on the rate of force development and the respective contributions of phosphorylation and crossbridge kinetics to differences between phasic and tonic smooth muscles; (c) the kinetics of the crossbridge cycle. We have also reviewed recent results obtained by other methods and bearing on the mechanisms of pharmacomechanical Ca2+ release and modulation of the Ca2+ sensitivity of the regulatory/contractile apparatus. 2. The long delay (1.5 at 22 degrees C) following activation of alpha 1-adrenergic receptors through photolysis of caged phenylephrine and the high Q10 of this process are consistent with the hypothesis that activation of phospholipase C is the major mechanism of alpha-adrenergic pharmacomechanical Ca2+ release. 3. The delay between photolysis of caged InsP3 and Ca2+ release is short: 30 ms or less, while the latency of contraction is significant (0.3-0.5 s at 22 degrees C) and similar to the lag between the rise in [Ca2+]i and force development in intact smooth muscles. The latency of contraction following photolysis of caged ATP in permeabilized muscles in rigor, in the presence of Ca2+ and calmodulin, is similar, about 0.2-0.5 s at 22 degrees C. 4. In muscles in which the myosin light chains are maintained in a phosphorylated state during rigor, photolysis of caged ATP initiates contractions with a short delay (10 ms or less). This result and those summarized above (2 and 3) suggest that the major portion of the delay between agonist-receptor interaction and contraction is due to activation of phospholipase C and InsP3 production, and about 0.2-0.5 s of the delay (22 degrees C) can be ascribed to prephosphorylation reactions between Ca2+, calmodulin, and myosin light chain kinase, and/or to mechanical processes, or to the chemical kinetics of two-step reactions. 5. Force development from rigor, initiated by photolysis of caged ATP in the presence of Ca2(+)-calmodulin, is rate-limited by myosin light chain phosphorylation; it is significantly accelerated if the myosin light chains are already phosphorylated prior to photolysis.(ABSTRACT TRUNCATED AT 400 WORDS)
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical | |
pubmed:status |
MEDLINE
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pubmed:issn |
0066-4278
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:volume |
52
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
857-74
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pubmed:dateRevised |
2007-11-14
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pubmed:meshHeading |
pubmed-meshheading:2184779-Animals,
pubmed-meshheading:2184779-Biomechanics,
pubmed-meshheading:2184779-Calcium,
pubmed-meshheading:2184779-Inositol Phosphates,
pubmed-meshheading:2184779-Kinetics,
pubmed-meshheading:2184779-Muscle, Smooth,
pubmed-meshheading:2184779-Muscle Contraction,
pubmed-meshheading:2184779-Phenylephrine,
pubmed-meshheading:2184779-Photochemistry,
pubmed-meshheading:2184779-Photolysis,
pubmed-meshheading:2184779-Reaction Time
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pubmed:year |
1990
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pubmed:articleTitle |
Flash photolysis studies of excitation-contraction coupling, regulation, and contraction in smooth muscle.
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pubmed:affiliation |
Department of Physiology, University of Virginia Health Sciences Center, Charlottesville 22908.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Review
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