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Effects of extracellular K+ and Ca2+ on membrane potential, contraction and 86Rb+ efflux in guinea-pig mesotubarium

Lydrup, M L and Hellstrand, Per LU (1990) In Pflügers Archiv 415(6). p.664-670
Abstract
The effects of varying extracellular concentrations of K+ and Ca2+ [K+]o and [Ca2+]o on force development and membrane potential were investigated in the guinea-pig mesotubarium. At [K+]o up to 40 mM, spontaneous action potentials were present, while higher [K+]o gave sustained contractures at a stable membrane potential (-24 to -12 mV for [K+]o from 60 to 120 mM). Tension decreased successively with increasing [K+]o from 30 to 120 mM. The relaxing potency of the dihydropyridine Ca2+ antagonist, felodipine, increased as the membrane was depolarized with increasing [K+]o and action potentials ceased. These results are compatible with the existence of Ca2+ channels showing voltage-dependent affinity with dihydrophyridines. Increasing [Ca2+]o... (More)
The effects of varying extracellular concentrations of K+ and Ca2+ [K+]o and [Ca2+]o on force development and membrane potential were investigated in the guinea-pig mesotubarium. At [K+]o up to 40 mM, spontaneous action potentials were present, while higher [K+]o gave sustained contractures at a stable membrane potential (-24 to -12 mV for [K+]o from 60 to 120 mM). Tension decreased successively with increasing [K+]o from 30 to 120 mM. The relaxing potency of the dihydropyridine Ca2+ antagonist, felodipine, increased as the membrane was depolarized with increasing [K+]o and action potentials ceased. These results are compatible with the existence of Ca2+ channels showing voltage-dependent affinity with dihydrophyridines. Increasing [Ca2+]o from 2.5 to 10 mM caused membrane hyperpolarization by about 11 mV and was accompanied by a lower frequency of spontaneous contractions and a longer duration of the relaxation between contractions. 86Rb+ efflux measurements in 60 mM K+ in the absence and presence of felodipine revealed a Ca2(+)-dependent component of the voltage-activated efflux. In normal solution (5.9 mM K+), efflux in the presence of felodipine was similar to the minimal value during normal spontaneous activity. The results indicate regulation of the permeability of K+ channels by the intracellular Ca2+ concentration ([Ca2+]i) and suggest participation of such channels in the generation of the regularly occurring bursts of action potentials characteristic of spontaneous activity in the mesotubarium. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Smooth muscle, Ion channels, Calcium, Potassium, Calcium antagonists, Contraction, Electrophysiology
in
Pflügers Archiv
volume
415
issue
6
pages
664 - 670
publisher
Springer
external identifiers
  • pmid:2336345
  • scopus:0025217284
ISSN
0031-6768
DOI
10.1007/BF02584003
language
English
LU publication?
yes
id
05ffebe3-123a-440e-b28d-bab8a09e8f41 (old id 1105285)
date added to LUP
2008-08-05 12:13:14
date last changed
2017-01-01 07:00:47
@article{05ffebe3-123a-440e-b28d-bab8a09e8f41,
  abstract     = {The effects of varying extracellular concentrations of K+ and Ca2+ [K+]o and [Ca2+]o on force development and membrane potential were investigated in the guinea-pig mesotubarium. At [K+]o up to 40 mM, spontaneous action potentials were present, while higher [K+]o gave sustained contractures at a stable membrane potential (-24 to -12 mV for [K+]o from 60 to 120 mM). Tension decreased successively with increasing [K+]o from 30 to 120 mM. The relaxing potency of the dihydropyridine Ca2+ antagonist, felodipine, increased as the membrane was depolarized with increasing [K+]o and action potentials ceased. These results are compatible with the existence of Ca2+ channels showing voltage-dependent affinity with dihydrophyridines. Increasing [Ca2+]o from 2.5 to 10 mM caused membrane hyperpolarization by about 11 mV and was accompanied by a lower frequency of spontaneous contractions and a longer duration of the relaxation between contractions. 86Rb+ efflux measurements in 60 mM K+ in the absence and presence of felodipine revealed a Ca2(+)-dependent component of the voltage-activated efflux. In normal solution (5.9 mM K+), efflux in the presence of felodipine was similar to the minimal value during normal spontaneous activity. The results indicate regulation of the permeability of K+ channels by the intracellular Ca2+ concentration ([Ca2+]i) and suggest participation of such channels in the generation of the regularly occurring bursts of action potentials characteristic of spontaneous activity in the mesotubarium.},
  author       = {Lydrup, M L and Hellstrand, Per},
  issn         = {0031-6768},
  keyword      = {Smooth muscle,Ion channels,Calcium,Potassium,Calcium antagonists,Contraction,Electrophysiology},
  language     = {eng},
  number       = {6},
  pages        = {664--670},
  publisher    = {Springer},
  series       = {Pflügers Archiv},
  title        = {Effects of extracellular K+ and Ca2+ on membrane potential, contraction and 86Rb+ efflux in guinea-pig mesotubarium},
  url          = {http://dx.doi.org/10.1007/BF02584003},
  volume       = {415},
  year         = {1990},
}