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Substrate and product dependence of force and shortening in fast and slow smooth muscle

Löfgren, Mia; Malmqvist, Ulf LU and Arner, Anders LU (2001) In Journal of General Physiology 117(5). p.407-418
Abstract
To explore the molecular mechanisms responsible for the variation in smooth muscle contractile kinetics, the influence of MgATP, MgADP, and inorganic phosphate (P(i)) on force and shortening velocity in thiophosphorylated "fast" (taenia coli: maximal shortening velocity Vmax = 0.11 ML/s) and "slow" (aorta: Vmax = 0.015 ML/s) smooth muscle from the guinea pig were compared. P(i) inhibited active force with minor effects on the V(max). In the taenia coli, 20 mM P(i) inhibited force by 25%. In the aorta, the effect was markedly less (< 10%), suggesting differences between fast and slow smooth muscles in the binding of P(i) or in the relative population of P(i) binding states during cycling. Lowering of MgATP reduced force and V(max). The... (More)
To explore the molecular mechanisms responsible for the variation in smooth muscle contractile kinetics, the influence of MgATP, MgADP, and inorganic phosphate (P(i)) on force and shortening velocity in thiophosphorylated "fast" (taenia coli: maximal shortening velocity Vmax = 0.11 ML/s) and "slow" (aorta: Vmax = 0.015 ML/s) smooth muscle from the guinea pig were compared. P(i) inhibited active force with minor effects on the V(max). In the taenia coli, 20 mM P(i) inhibited force by 25%. In the aorta, the effect was markedly less (< 10%), suggesting differences between fast and slow smooth muscles in the binding of P(i) or in the relative population of P(i) binding states during cycling. Lowering of MgATP reduced force and V(max). The aorta was less sensitive to reduction in MgATP (Km for Vmax: 80 microM) than the taenia coli (Km for Vmax: 350 microM). Thus, velocity is controlled by steps preceding the ATP binding and cross-bridge dissociation, and a weaker binding of ATP is not responsible for the lower V(max) in the slow muscle. MgADP inhibited force and V(max). Saturating concentrations of ADP did not completely inhibit maximal shortening velocity. The effect of ADP on Vmax was observed at lower concentrations in the aorta compared with the taenia coli, suggesting that the ADP binding to phosphorylated and cycling cross-bridges is stronger in slow compared with fast smooth muscle. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ADP, ATP, phosphate, myosin isoforms, force-velocity relation
in
Journal of General Physiology
volume
117
issue
5
pages
407 - 418
publisher
Rockefeller Institute for Medical Research
external identifiers
  • pmid:11331350
  • scopus:0343338187
ISSN
0022-1295
DOI
10.1085/jgp.117.5.407
language
English
LU publication?
yes
id
cb9ff940-bd8e-4f03-a423-9a1d86912fbb (old id 1122731)
date added to LUP
2008-07-04 11:02:30
date last changed
2018-01-07 09:33:13
@article{cb9ff940-bd8e-4f03-a423-9a1d86912fbb,
  abstract     = {To explore the molecular mechanisms responsible for the variation in smooth muscle contractile kinetics, the influence of MgATP, MgADP, and inorganic phosphate (P(i)) on force and shortening velocity in thiophosphorylated "fast" (taenia coli: maximal shortening velocity Vmax = 0.11 ML/s) and "slow" (aorta: Vmax = 0.015 ML/s) smooth muscle from the guinea pig were compared. P(i) inhibited active force with minor effects on the V(max). In the taenia coli, 20 mM P(i) inhibited force by 25%. In the aorta, the effect was markedly less (&lt; 10%), suggesting differences between fast and slow smooth muscles in the binding of P(i) or in the relative population of P(i) binding states during cycling. Lowering of MgATP reduced force and V(max). The aorta was less sensitive to reduction in MgATP (Km for Vmax: 80 microM) than the taenia coli (Km for Vmax: 350 microM). Thus, velocity is controlled by steps preceding the ATP binding and cross-bridge dissociation, and a weaker binding of ATP is not responsible for the lower V(max) in the slow muscle. MgADP inhibited force and V(max). Saturating concentrations of ADP did not completely inhibit maximal shortening velocity. The effect of ADP on Vmax was observed at lower concentrations in the aorta compared with the taenia coli, suggesting that the ADP binding to phosphorylated and cycling cross-bridges is stronger in slow compared with fast smooth muscle.},
  author       = {Löfgren, Mia and Malmqvist, Ulf and Arner, Anders},
  issn         = {0022-1295},
  keyword      = {ADP,ATP,phosphate,myosin isoforms,force-velocity relation},
  language     = {eng},
  number       = {5},
  pages        = {407--418},
  publisher    = {Rockefeller Institute for Medical Research},
  series       = {Journal of General Physiology},
  title        = {Substrate and product dependence of force and shortening in fast and slow smooth muscle},
  url          = {http://dx.doi.org/10.1085/jgp.117.5.407},
  volume       = {117},
  year         = {2001},
}