Advanced

Activation of contraction and ATPase activity in intact and chemically skinned smooth muscle of rat portal vein. Dependence on Ca++ and muscle length

Arner, Anders LU and Hellstrand, Per LU (1983) In Circulation Research 53(5). p.695-702
Abstract
The mechanical manifestations of muscle contraction (force development or shortening) are accompanied by an increased turnover of chemical energy (ATPase activity, JATP). In intact rat portal veins activated by high potassium medium to produce graded contractions at different levels of extracellular calcium, a linear dependence of oxygen consumption on force was found. The slope of the relation (metabolic tension cost) was higher during early stages than during late stages of contraction, possibly reflecting a transient high crossbridge ATP turnover rate. Chemically skinned (Triton X-100) rat portal vein preparations were used to study the energy turnover of the smooth muscle contractile system under constant activation. In these... (More)
The mechanical manifestations of muscle contraction (force development or shortening) are accompanied by an increased turnover of chemical energy (ATPase activity, JATP). In intact rat portal veins activated by high potassium medium to produce graded contractions at different levels of extracellular calcium, a linear dependence of oxygen consumption on force was found. The slope of the relation (metabolic tension cost) was higher during early stages than during late stages of contraction, possibly reflecting a transient high crossbridge ATP turnover rate. Chemically skinned (Triton X-100) rat portal vein preparations were used to study the energy turnover of the smooth muscle contractile system under constant activation. In these preparations, JATP increased on activation by calcium in the presence of 1 microM calmodulin, remained constant for maintained contractures, and decreased promptly on relaxation. Force declined with each repeated contraction at optimal calcium level (10(-4.5) M), but the relation between force and JATP remained invariant and agreed with that of the intact muscle during the transient of high ATP turnover. Calcium activation in the range 10(-9) to 10(-4.5) M caused a progressively steeper (nonlinear) increase in JATP with force. Length-force relations showed a lower relative force at muscle lengths below L0 in the intact than in the skinned tissue, possibly indicating depression of excitation-contraction coupling. The slope of the relation between JATP and force was lower when length was varied than when calcium was varied. At a length where no external force was produced, the activated muscle had a significantly higher JATP than while relaxed (10(-9) M Ca++). Together with previous results showing calcium dependence of the force-velocity relation, the present study indicates an influence of calcium on crossbridge kinetics in smooth muscle. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Circulation Research
volume
53
issue
5
pages
695 - 702
publisher
American Heart Association
external identifiers
  • pmid:6226453
  • scopus:0021083745
ISSN
0009-7330
language
English
LU publication?
yes
id
74a7c665-fe83-4a09-bb8b-4c690766b1d5 (old id 1103101)
alternative location
http://circres.ahajournals.org/cgi/reprint/53/5/695
date added to LUP
2008-08-13 09:48:46
date last changed
2017-01-01 06:42:03
@article{74a7c665-fe83-4a09-bb8b-4c690766b1d5,
  abstract     = {The mechanical manifestations of muscle contraction (force development or shortening) are accompanied by an increased turnover of chemical energy (ATPase activity, JATP). In intact rat portal veins activated by high potassium medium to produce graded contractions at different levels of extracellular calcium, a linear dependence of oxygen consumption on force was found. The slope of the relation (metabolic tension cost) was higher during early stages than during late stages of contraction, possibly reflecting a transient high crossbridge ATP turnover rate. Chemically skinned (Triton X-100) rat portal vein preparations were used to study the energy turnover of the smooth muscle contractile system under constant activation. In these preparations, JATP increased on activation by calcium in the presence of 1 microM calmodulin, remained constant for maintained contractures, and decreased promptly on relaxation. Force declined with each repeated contraction at optimal calcium level (10(-4.5) M), but the relation between force and JATP remained invariant and agreed with that of the intact muscle during the transient of high ATP turnover. Calcium activation in the range 10(-9) to 10(-4.5) M caused a progressively steeper (nonlinear) increase in JATP with force. Length-force relations showed a lower relative force at muscle lengths below L0 in the intact than in the skinned tissue, possibly indicating depression of excitation-contraction coupling. The slope of the relation between JATP and force was lower when length was varied than when calcium was varied. At a length where no external force was produced, the activated muscle had a significantly higher JATP than while relaxed (10(-9) M Ca++). Together with previous results showing calcium dependence of the force-velocity relation, the present study indicates an influence of calcium on crossbridge kinetics in smooth muscle.},
  author       = {Arner, Anders and Hellstrand, Per},
  issn         = {0009-7330},
  language     = {eng},
  number       = {5},
  pages        = {695--702},
  publisher    = {American Heart Association},
  series       = {Circulation Research},
  title        = {Activation of contraction and ATPase activity in intact and chemically skinned smooth muscle of rat portal vein. Dependence on Ca++ and muscle length},
  volume       = {53},
  year         = {1983},
}