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Dissociation of phosphorylase a activation and contractile activity in rat portal vein

Paul, R J and Hellstrand, Per LU (1984) In Acta Physiologica Scandinavica 121(1). p.23-30
Abstract
Isometric force, glycogen phosphorylase activity and lactate production were measured under conditions known to alter intracellular Ca2+ and cAMP to assess the role of these messengers in the coordination of metabolism with contractility in rat portal vein. Total phosphorylase (a + b) activity, was independent of treatment. The activity ratio phosphorylase activity ratio in the presence of isoproterenol and papaverine was dependent on or high-K+ medium, and 0.57 after 20 min treatment with 10(-5) M isoproterenol + 10(-4) M papaverine. Under both of these conditions the muscle was totally relaxed. The phosphorylase activity ratio in the presence of isoproterenol and papaverine was dependent on extracellular Ca2+, both in normal and... (More)
Isometric force, glycogen phosphorylase activity and lactate production were measured under conditions known to alter intracellular Ca2+ and cAMP to assess the role of these messengers in the coordination of metabolism with contractility in rat portal vein. Total phosphorylase (a + b) activity, was independent of treatment. The activity ratio phosphorylase activity ratio in the presence of isoproterenol and papaverine was dependent on or high-K+ medium, and 0.57 after 20 min treatment with 10(-5) M isoproterenol + 10(-4) M papaverine. Under both of these conditions the muscle was totally relaxed. The phosphorylase activity ratio in the presence of isoproterenol and papaverine was dependent on extracellular Ca2+, both in normal and depolarizing medium. This suggests a lower Ca2+ sensitivity of the contractile than the phosphorylase system under these conditions, known to be associated with raised intracellular cAMP. During spontaneous activity and high-K+ induced contractures phosphorylase activity was increased compared to the relaxed state in Ca2+-free medium. A high level of phosphorylase activity (0.48) was elicited by the addition of 300 mM sucrose, which induces a contracture in Ca2+-free medium. Lactate production was in general parallel to phosphorylase activity, except for a relative increase in anoxia. The results suggest that in the intact cell the Ca2+-mediated linkage of contraction and phosphorylase may be modified by cAMP changing the Ca2+ sensitivities of the two systems in opposite directions. (Less)
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Contribution to journal
publication status
published
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in
Acta Physiologica Scandinavica
volume
121
issue
1
pages
23 - 30
publisher
Wiley-Blackwell
external identifiers
  • pmid:6331075
  • scopus:0021142695
ISSN
0001-6772
language
English
LU publication?
yes
id
73cc0bc1-0eb8-4d37-85d3-3afd3925a42a (old id 1103284)
date added to LUP
2008-08-12 15:35:44
date last changed
2017-01-01 07:09:00
@article{73cc0bc1-0eb8-4d37-85d3-3afd3925a42a,
  abstract     = {Isometric force, glycogen phosphorylase activity and lactate production were measured under conditions known to alter intracellular Ca2+ and cAMP to assess the role of these messengers in the coordination of metabolism with contractility in rat portal vein. Total phosphorylase (a + b) activity, was independent of treatment. The activity ratio phosphorylase activity ratio in the presence of isoproterenol and papaverine was dependent on or high-K+ medium, and 0.57 after 20 min treatment with 10(-5) M isoproterenol + 10(-4) M papaverine. Under both of these conditions the muscle was totally relaxed. The phosphorylase activity ratio in the presence of isoproterenol and papaverine was dependent on extracellular Ca2+, both in normal and depolarizing medium. This suggests a lower Ca2+ sensitivity of the contractile than the phosphorylase system under these conditions, known to be associated with raised intracellular cAMP. During spontaneous activity and high-K+ induced contractures phosphorylase activity was increased compared to the relaxed state in Ca2+-free medium. A high level of phosphorylase activity (0.48) was elicited by the addition of 300 mM sucrose, which induces a contracture in Ca2+-free medium. Lactate production was in general parallel to phosphorylase activity, except for a relative increase in anoxia. The results suggest that in the intact cell the Ca2+-mediated linkage of contraction and phosphorylase may be modified by cAMP changing the Ca2+ sensitivities of the two systems in opposite directions.},
  author       = {Paul, R J and Hellstrand, Per},
  issn         = {0001-6772},
  language     = {eng},
  number       = {1},
  pages        = {23--30},
  publisher    = {Wiley-Blackwell},
  series       = {Acta Physiologica Scandinavica},
  title        = {Dissociation of phosphorylase a activation and contractile activity in rat portal vein},
  volume       = {121},
  year         = {1984},
}