Advanced

Shortening velocity, myosin light chain phosphorylation and Ca2+ dependence of force during metabolic inhibition in smooth muscle of rat portal vein

Ekmehag, Björn LU and Hellstrand, Per LU (1989) In Acta Physiologica Scandinavica 136(3). p.367-376
Abstract
The concentration-response relation for Ca2+ (0.2-5.0 mM) of high-K+ contractures (40 mM) in the rat portal vein during respiratory inhibition by 0.2 mM cyanide was investigated. A reduction of force in the presence of cyanide to about 30% of control was associated with a leftward shift of the normalized concentration-response relation. When force at the plateau of high-K+ contractures (at about 2 min) was reduced to 65 +/- 2% due to the addition of cyanide, the maximal shortening velocity (Vmax) was 94 +/- 5% of control (n = 6). In electrically (AC) stimulated preparations giving short tetanic contractions, a reduction of active force to 58 +/- 2% of control in the presence of cyanide was associated with a reduction of Vmax to 83 +/- 5%... (More)
The concentration-response relation for Ca2+ (0.2-5.0 mM) of high-K+ contractures (40 mM) in the rat portal vein during respiratory inhibition by 0.2 mM cyanide was investigated. A reduction of force in the presence of cyanide to about 30% of control was associated with a leftward shift of the normalized concentration-response relation. When force at the plateau of high-K+ contractures (at about 2 min) was reduced to 65 +/- 2% due to the addition of cyanide, the maximal shortening velocity (Vmax) was 94 +/- 5% of control (n = 6). In electrically (AC) stimulated preparations giving short tetanic contractions, a reduction of active force to 58 +/- 2% of control in the presence of cyanide was associated with a reduction of Vmax to 83 +/- 5% (n = 7). Phosphorylation of the 20-kDa regulatory light chains (LC20) of the myosin molecule was studied in the relaxed state and at the plateau of high-K+ contractures for comparison with the mechanical data. Both control and cyanide-treated preparations showed 9% LC20 phosphorylation in nominally Ca2+-free solution (n = 6). After activation the level of phosphorylation increased to 30 +/- 3% (n = 9) in the control veins. In cyanide-treated veins, where force was reduced to 42 +/- 6% compared to a preceding control period, the phosphorylation level was 17 +/- 2% (n = 7). The study suggests that the mechanical changes caused by inhibition of cellular respiration may involve the combined effect of several metabolic alterations, including decreased LC20 phosphorylation during contraction, but apparently not decreased intracellular Ca2+ concentration or sensitivity of the contractile system to Ca2+. (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
Acta Physiologica Scandinavica
volume
136
issue
3
pages
367 - 376
publisher
Wiley-Blackwell
external identifiers
  • pmid:2750537
  • scopus:0024340178
ISSN
0001-6772
language
English
LU publication?
yes
id
b0ea9008-2793-4e5e-a466-599e0ccaf227 (old id 1104640)
date added to LUP
2008-08-06 12:12:43
date last changed
2017-08-20 04:23:37
@article{b0ea9008-2793-4e5e-a466-599e0ccaf227,
  abstract     = {The concentration-response relation for Ca2+ (0.2-5.0 mM) of high-K+ contractures (40 mM) in the rat portal vein during respiratory inhibition by 0.2 mM cyanide was investigated. A reduction of force in the presence of cyanide to about 30% of control was associated with a leftward shift of the normalized concentration-response relation. When force at the plateau of high-K+ contractures (at about 2 min) was reduced to 65 +/- 2% due to the addition of cyanide, the maximal shortening velocity (Vmax) was 94 +/- 5% of control (n = 6). In electrically (AC) stimulated preparations giving short tetanic contractions, a reduction of active force to 58 +/- 2% of control in the presence of cyanide was associated with a reduction of Vmax to 83 +/- 5% (n = 7). Phosphorylation of the 20-kDa regulatory light chains (LC20) of the myosin molecule was studied in the relaxed state and at the plateau of high-K+ contractures for comparison with the mechanical data. Both control and cyanide-treated preparations showed 9% LC20 phosphorylation in nominally Ca2+-free solution (n = 6). After activation the level of phosphorylation increased to 30 +/- 3% (n = 9) in the control veins. In cyanide-treated veins, where force was reduced to 42 +/- 6% compared to a preceding control period, the phosphorylation level was 17 +/- 2% (n = 7). The study suggests that the mechanical changes caused by inhibition of cellular respiration may involve the combined effect of several metabolic alterations, including decreased LC20 phosphorylation during contraction, but apparently not decreased intracellular Ca2+ concentration or sensitivity of the contractile system to Ca2+.},
  author       = {Ekmehag, Björn and Hellstrand, Per},
  issn         = {0001-6772},
  language     = {eng},
  number       = {3},
  pages        = {367--376},
  publisher    = {Wiley-Blackwell},
  series       = {Acta Physiologica Scandinavica},
  title        = {Shortening velocity, myosin light chain phosphorylation and Ca2+ dependence of force during metabolic inhibition in smooth muscle of rat portal vein},
  volume       = {136},
  year         = {1989},
}