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Isometric and isotonic relaxation in venous smooth muscle

Johansson, B and Hellstrand, Per LU (1975) In Acta Physiologica Scandinavica 93(2). p.167-174
Abstract
The time course of relaxation under isometric and isotonic conditions was studied in preparations of rat portal vein which maintained regular phasic contractions in solutions with increased [K-+] and [Ca-2+]. It was found that the smooth muscle during isotonic lengthening was able to carry the afterload for a period of time which was longer than expected from the control isometric response. The difference was largest for afterloads corresponding to about half the isometric peak force. The terminal decline in force was identical in afterloaded and purely isometric responses. Inhibitory influences of isotonic shortening causing increased rates of relaxation, as reported for striated muscles, were not observed. The differences in the course... (More)
The time course of relaxation under isometric and isotonic conditions was studied in preparations of rat portal vein which maintained regular phasic contractions in solutions with increased [K-+] and [Ca-2+]. It was found that the smooth muscle during isotonic lengthening was able to carry the afterload for a period of time which was longer than expected from the control isometric response. The difference was largest for afterloads corresponding to about half the isometric peak force. The terminal decline in force was identical in afterloaded and purely isometric responses. Inhibitory influences of isotonic shortening causing increased rates of relaxation, as reported for striated muscles, were not observed. The differences in the course of relaxation between isotonic and isometric responses of portal vein could not be attributed to variations in membrane excitation. It also appears that the differences are not due to changes in release or uptake of activator calcium, or to presence of viscous elements in the tissue. It is suggested that the ability of the smooth muscle to carry load over a relatively long period during isotonic relaxation may be attributed to the characteristics of the instantaneous force-velocity relations in the force range above Po. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Acta Physiologica Scandinavica
volume
93
issue
2
pages
167 - 174
publisher
Wiley-Blackwell
external identifiers
  • pmid:1146569
  • scopus:0016680133
ISSN
0001-6772
language
English
LU publication?
yes
id
ea30fa65-a751-4367-8544-7ff98b6bc7bb (old id 1102588)
date added to LUP
2008-08-14 12:56:57
date last changed
2017-01-01 07:22:58
@article{ea30fa65-a751-4367-8544-7ff98b6bc7bb,
  abstract     = {The time course of relaxation under isometric and isotonic conditions was studied in preparations of rat portal vein which maintained regular phasic contractions in solutions with increased [K-+] and [Ca-2+]. It was found that the smooth muscle during isotonic lengthening was able to carry the afterload for a period of time which was longer than expected from the control isometric response. The difference was largest for afterloads corresponding to about half the isometric peak force. The terminal decline in force was identical in afterloaded and purely isometric responses. Inhibitory influences of isotonic shortening causing increased rates of relaxation, as reported for striated muscles, were not observed. The differences in the course of relaxation between isotonic and isometric responses of portal vein could not be attributed to variations in membrane excitation. It also appears that the differences are not due to changes in release or uptake of activator calcium, or to presence of viscous elements in the tissue. It is suggested that the ability of the smooth muscle to carry load over a relatively long period during isotonic relaxation may be attributed to the characteristics of the instantaneous force-velocity relations in the force range above Po.},
  author       = {Johansson, B and Hellstrand, Per},
  issn         = {0001-6772},
  language     = {eng},
  number       = {2},
  pages        = {167--174},
  publisher    = {Wiley-Blackwell},
  series       = {Acta Physiologica Scandinavica},
  title        = {Isometric and isotonic relaxation in venous smooth muscle},
  volume       = {93},
  year         = {1975},
}