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The force-velocity relation in phasic contractions of venous smooth muscle

Hellstrand, Per LU and Johansson, B (1975) In Acta Physiologica Scandinavica 93(2). p.157-166
Abstract
The force-velocity relation of the rat portal vein has been studied during regular spontaneous contractions induced by elevated levels of [K-+]O AND [Ca-2+]o. No satisfactory description of the force-velocity relation was obtained by measuring shortening velocity in afterloaded isotonic contractions. Therefore the method of isotonic quick release was used, as this permits mechanical studies at specified instants of the contraction-relaxation cycle. The temporal development of the force-velocity relation in the phasic response was investigated. During a time interval in the rising phase of the contraction, at about the time for maximal dP/dt, the force-velicity curves were practically identical, suggesting a plateau in the intensity of... (More)
The force-velocity relation of the rat portal vein has been studied during regular spontaneous contractions induced by elevated levels of [K-+]O AND [Ca-2+]o. No satisfactory description of the force-velocity relation was obtained by measuring shortening velocity in afterloaded isotonic contractions. Therefore the method of isotonic quick release was used, as this permits mechanical studies at specified instants of the contraction-relaxation cycle. The temporal development of the force-velocity relation in the phasic response was investigated. During a time interval in the rising phase of the contraction, at about the time for maximal dP/dt, the force-velicity curves were practically identical, suggesting a plateau in the intensity of active state. At later stages of the twitch the curves were progressively displaced towards the origin, the intercepts on both the force and the velocity axis becoming smaller. At the time of the isometric peak the maximal shortening velocity had declined relatively more than the isometric force. This is presumably caused by inhomogeneous activation of the muscle at the beginning of relaxation, The maximal force-velocity relation in the rising phase of the contraction can be described by Hill's (1938) equation with the following parameters (at 37 degrees tc): a/Po = 0.73 plus or minus 0.04, b = 0.54 plus or minus 0.04 lengths/s, Vmax = 0.74 plus or minus 0.02 lengths/s (n = 7, mean plus or minus S.E,). The force-velocity relation of the portal vein in comparison with other kinds of muscle is discussed. (Less)
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organization
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type
Contribution to journal
publication status
published
subject
in
Acta Physiologica Scandinavica
volume
93
issue
2
pages
157 - 166
publisher
Wiley-Blackwell
external identifiers
  • pmid:1146568
  • scopus:0016733676
ISSN
0001-6772
language
English
LU publication?
yes
id
d400c175-eb68-4204-b944-665623db4648 (old id 1102590)
date added to LUP
2008-08-14 12:57:37
date last changed
2017-07-30 04:33:20
@article{d400c175-eb68-4204-b944-665623db4648,
  abstract     = {The force-velocity relation of the rat portal vein has been studied during regular spontaneous contractions induced by elevated levels of [K-+]O AND [Ca-2+]o. No satisfactory description of the force-velocity relation was obtained by measuring shortening velocity in afterloaded isotonic contractions. Therefore the method of isotonic quick release was used, as this permits mechanical studies at specified instants of the contraction-relaxation cycle. The temporal development of the force-velocity relation in the phasic response was investigated. During a time interval in the rising phase of the contraction, at about the time for maximal dP/dt, the force-velicity curves were practically identical, suggesting a plateau in the intensity of active state. At later stages of the twitch the curves were progressively displaced towards the origin, the intercepts on both the force and the velocity axis becoming smaller. At the time of the isometric peak the maximal shortening velocity had declined relatively more than the isometric force. This is presumably caused by inhomogeneous activation of the muscle at the beginning of relaxation, The maximal force-velocity relation in the rising phase of the contraction can be described by Hill's (1938) equation with the following parameters (at 37 degrees tc): a/Po = 0.73 plus or minus 0.04, b = 0.54 plus or minus 0.04 lengths/s, Vmax = 0.74 plus or minus 0.02 lengths/s (n = 7, mean plus or minus S.E,). The force-velocity relation of the portal vein in comparison with other kinds of muscle is discussed.},
  author       = {Hellstrand, Per and Johansson, B},
  issn         = {0001-6772},
  language     = {eng},
  number       = {2},
  pages        = {157--166},
  publisher    = {Wiley-Blackwell},
  series       = {Acta Physiologica Scandinavica},
  title        = {The force-velocity relation in phasic contractions of venous smooth muscle},
  volume       = {93},
  year         = {1975},
}