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Cross-bridge kinetics during shortening in early and sustained contraction of intestinal smooth muscle

Hellstrand, Per LU and Nordström, Ina LU (1993) In American Journal of Physiology 265(3 Pt 1). p.695-703
Abstract
Mechanisms responsible for the decrease in shortening velocity after prolonged contraction ("latch" state) were investigated at identical force during early (20 s, "phasic") and sustained (5 min, "tonic") phases of high-K+ (25-30 mM) contractions in smooth muscle of guinea pig taenia coli. Cytoplasmic Ca2+ concentration, myosin light-chain phosphorylation, and maximum shortening velocity all declined from 20 s to 5 min of contraction. The time course of shortening following isotonic quick release was biexponential, with a fastest rate constant of approximately 80 s-1 in both phasic and tonic contractions. Stiffness was identical in phasic and tonic contraction; however, after a release to slack length and unloaded shortening, stiffness... (More)
Mechanisms responsible for the decrease in shortening velocity after prolonged contraction ("latch" state) were investigated at identical force during early (20 s, "phasic") and sustained (5 min, "tonic") phases of high-K+ (25-30 mM) contractions in smooth muscle of guinea pig taenia coli. Cytoplasmic Ca2+ concentration, myosin light-chain phosphorylation, and maximum shortening velocity all declined from 20 s to 5 min of contraction. The time course of shortening following isotonic quick release was biexponential, with a fastest rate constant of approximately 80 s-1 in both phasic and tonic contractions. Stiffness was identical in phasic and tonic contraction; however, after a release to slack length and unloaded shortening, stiffness during restretch was greater in tonic contraction (51 vs. 43% of isometric stiffness after 16 ms of unloaded shortening). Stiffness decreased after release with a rate constant of approximately 200 s-1, slightly greater in phasic than in tonic contraction. The results indicate that the number of attached cross bridges during unloaded shortening, while substantially reduced relative to the isometric value, is higher in latch than in nonlatch, consistent with a lower detachment relative to attachment rate. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
American Journal of Physiology
volume
265
issue
3 Pt 1
pages
695 - 703
publisher
American Pysiological Society
external identifiers
  • pmid:8214026
  • scopus:0027666049
ISSN
0002-9513
language
English
LU publication?
yes
id
962f1721-31b0-42b2-9a36-ff711534e25e (old id 1107369)
date added to LUP
2008-07-30 16:55:19
date last changed
2017-01-01 07:25:51
@article{962f1721-31b0-42b2-9a36-ff711534e25e,
  abstract     = {Mechanisms responsible for the decrease in shortening velocity after prolonged contraction ("latch" state) were investigated at identical force during early (20 s, "phasic") and sustained (5 min, "tonic") phases of high-K+ (25-30 mM) contractions in smooth muscle of guinea pig taenia coli. Cytoplasmic Ca2+ concentration, myosin light-chain phosphorylation, and maximum shortening velocity all declined from 20 s to 5 min of contraction. The time course of shortening following isotonic quick release was biexponential, with a fastest rate constant of approximately 80 s-1 in both phasic and tonic contractions. Stiffness was identical in phasic and tonic contraction; however, after a release to slack length and unloaded shortening, stiffness during restretch was greater in tonic contraction (51 vs. 43% of isometric stiffness after 16 ms of unloaded shortening). Stiffness decreased after release with a rate constant of approximately 200 s-1, slightly greater in phasic than in tonic contraction. The results indicate that the number of attached cross bridges during unloaded shortening, while substantially reduced relative to the isometric value, is higher in latch than in nonlatch, consistent with a lower detachment relative to attachment rate.},
  author       = {Hellstrand, Per and Nordström, Ina},
  issn         = {0002-9513},
  language     = {eng},
  number       = {3 Pt 1},
  pages        = {695--703},
  publisher    = {American Pysiological Society},
  series       = {American Journal of Physiology},
  title        = {Cross-bridge kinetics during shortening in early and sustained contraction of intestinal smooth muscle},
  volume       = {265},
  year         = {1993},
}