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Paradoxical decrease in cytosolic calcium with increasing depolarization by potassium in guinea-pig mesotubarium smooth muscle

Lydrup, M L; Himpens, B; Droogmans, G; Hellstrand, Per LU and Somlyo, A P (1992) In Pflügers Archiv 420(5-6). p.428-433
Abstract
The free intracellular Ca2+ concentration ([Ca2+]i) was measured simultaneously with isometric force in strips of guinea-pig mesotubarium using the Fura-2 technique. [Ca2+]i and force were maximal at a relatively low (30 mM) concentration of extracellular K+ ([K+]o), and declined at 90 and 140 mM K+. Plateau values of both [Ca2+]i and force were higher in the presence of 5.10(-6) M ryanodine, indicating that the sarcoplasmic reticulum (SR) contributes to the decline with depolarization. Force and [Ca2+]i at 90 mM K+ were both lower then the high-K+ solution was applied after a period in 30 mM K+ than after a period in normal solution (5.9 mM K+), consistent with inactivation of Ca2+ channels during prolonged depolarization. Addition of... (More)
The free intracellular Ca2+ concentration ([Ca2+]i) was measured simultaneously with isometric force in strips of guinea-pig mesotubarium using the Fura-2 technique. [Ca2+]i and force were maximal at a relatively low (30 mM) concentration of extracellular K+ ([K+]o), and declined at 90 and 140 mM K+. Plateau values of both [Ca2+]i and force were higher in the presence of 5.10(-6) M ryanodine, indicating that the sarcoplasmic reticulum (SR) contributes to the decline with depolarization. Force and [Ca2+]i at 90 mM K+ were both lower then the high-K+ solution was applied after a period in 30 mM K+ than after a period in normal solution (5.9 mM K+), consistent with inactivation of Ca2+ channels during prolonged depolarization. Addition of carbachol to the depolarized muscle caused a maintained increase in force without maintained increase in [Ca2+]i. We conclude that the decrease in force at increased [K+]o (the "calcium-potassium paradox") is due to a membrane-potential-mediated decrease in [Ca2+]i and, to a lesser extent, to desensitization of the contractile-regulatory apparatus to Ca2+. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Calcium, Mesotubarium, Smooth muscle, Fura-2, K+ depolarization
in
Pflügers Archiv
volume
420
issue
5-6
pages
428 - 433
publisher
Springer
external identifiers
  • pmid:1377377
  • scopus:0026697081
ISSN
0031-6768
DOI
10.1007/BF00374616
language
English
LU publication?
yes
id
a828fe47-3869-4d2a-9e52-cf4280bdc038 (old id 1106622)
date added to LUP
2008-08-08 12:57:53
date last changed
2017-01-01 07:23:48
@article{a828fe47-3869-4d2a-9e52-cf4280bdc038,
  abstract     = {The free intracellular Ca2+ concentration ([Ca2+]i) was measured simultaneously with isometric force in strips of guinea-pig mesotubarium using the Fura-2 technique. [Ca2+]i and force were maximal at a relatively low (30 mM) concentration of extracellular K+ ([K+]o), and declined at 90 and 140 mM K+. Plateau values of both [Ca2+]i and force were higher in the presence of 5.10(-6) M ryanodine, indicating that the sarcoplasmic reticulum (SR) contributes to the decline with depolarization. Force and [Ca2+]i at 90 mM K+ were both lower then the high-K+ solution was applied after a period in 30 mM K+ than after a period in normal solution (5.9 mM K+), consistent with inactivation of Ca2+ channels during prolonged depolarization. Addition of carbachol to the depolarized muscle caused a maintained increase in force without maintained increase in [Ca2+]i. We conclude that the decrease in force at increased [K+]o (the "calcium-potassium paradox") is due to a membrane-potential-mediated decrease in [Ca2+]i and, to a lesser extent, to desensitization of the contractile-regulatory apparatus to Ca2+.},
  author       = {Lydrup, M L and Himpens, B and Droogmans, G and Hellstrand, Per and Somlyo, A P},
  issn         = {0031-6768},
  keyword      = {Calcium,Mesotubarium,Smooth muscle,Fura-2,K+ depolarization},
  language     = {eng},
  number       = {5-6},
  pages        = {428--433},
  publisher    = {Springer},
  series       = {Pflügers Archiv},
  title        = {Paradoxical decrease in cytosolic calcium with increasing depolarization by potassium in guinea-pig mesotubarium smooth muscle},
  url          = {http://dx.doi.org/10.1007/BF00374616},
  volume       = {420},
  year         = {1992},
}