Regulation of force and shortening velocity by calcium and myosin phosphorylation in chemically skinned smooth muscle
(1996) In Pflügers Archiv 433(1-2). p.42-48- Abstract
- The phosphatase inhibitor okadaic acid (OA) was used to study the relationship between [Ca2+], rates of phosphorylation/dephosphorylation and the mechanical properties of smooth muscle fibres. Force/velocity relationships were determined with the isotonic quick release technique in chemically skinned guinea-pig taenia coli muscles at 22 degrees C. In the maximally thiophosphorylated muscle neither OA (10 microM) nor Ca2+ (increase from pCa 9.0 to pCa 4.5) influenced the force-velocity relationship. When the degree of activation was altered by varying [Ca2+] in the presence of 0.5 microM calmodulin, both force and the maximal shortening velocity (Vmax) were altered. At pCa 5.75, at which force was about 35% of the maximal at pCa 4.5, Vmax... (More)
- The phosphatase inhibitor okadaic acid (OA) was used to study the relationship between [Ca2+], rates of phosphorylation/dephosphorylation and the mechanical properties of smooth muscle fibres. Force/velocity relationships were determined with the isotonic quick release technique in chemically skinned guinea-pig taenia coli muscles at 22 degrees C. In the maximally thiophosphorylated muscle neither OA (10 microM) nor Ca2+ (increase from pCa 9.0 to pCa 4.5) influenced the force-velocity relationship. When the degree of activation was altered by varying [Ca2+] in the presence of 0.5 microM calmodulin, both force and the maximal shortening velocity (Vmax) were altered. At pCa 5.75, at which force was about 35% of the maximal at pCa 4.5, Vmax was 55% of the maximal value. When OA was introduced into fibres at pCa 6.0, force was increased from less than 5% to 100% of the maximal force obtained in pCa 4.5. The relationship between the degree of myosin light chain phosphorylation and force was similar in the two types of activation; varied [OA] at constant [Ca2+] and at varied [Ca2+]. The relation between force and Vmax when the degree of activation was altered with OA was almost identical to that obtained with varied [Ca2+]. The results show that Ca2+ and OA do not influence force or Vmax in the maximally phosphorylated state and suggest that the level of myosin light chain phosphorylation is the major factor determining Vmax. The finding that the relationship between force and Vmax was similar when activation was altered with OA and Ca2+ suggests, however, that alterations in the absolute rates of phosphorylation and dephosphorylation at a constant phosphorylation level do not influence the mechanical properties of the skinned smooth muscle fibres. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1110907
- author
- Malmqvist, Ulf LU and Arner, A
- organization
- publishing date
- 1996
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Okadaic acid, Myosin light chain phosphorylation, Skinned fibres, Force-velocity relation
- in
- Pflügers Archiv
- volume
- 433
- issue
- 1-2
- pages
- 42 - 48
- publisher
- Springer
- external identifiers
-
- pmid:9019729
- scopus:0029806862
- ISSN
- 0031-6768
- DOI
- 10.1007/s004240050246
- language
- English
- LU publication?
- yes
- id
- 6f0245a0-22ea-460a-ab27-ada4be1c3ac6 (old id 1110907)
- date added to LUP
- 2016-04-01 15:18:25
- date last changed
- 2022-01-28 04:43:10
@article{6f0245a0-22ea-460a-ab27-ada4be1c3ac6,
abstract = {{The phosphatase inhibitor okadaic acid (OA) was used to study the relationship between [Ca2+], rates of phosphorylation/dephosphorylation and the mechanical properties of smooth muscle fibres. Force/velocity relationships were determined with the isotonic quick release technique in chemically skinned guinea-pig taenia coli muscles at 22 degrees C. In the maximally thiophosphorylated muscle neither OA (10 microM) nor Ca2+ (increase from pCa 9.0 to pCa 4.5) influenced the force-velocity relationship. When the degree of activation was altered by varying [Ca2+] in the presence of 0.5 microM calmodulin, both force and the maximal shortening velocity (Vmax) were altered. At pCa 5.75, at which force was about 35% of the maximal at pCa 4.5, Vmax was 55% of the maximal value. When OA was introduced into fibres at pCa 6.0, force was increased from less than 5% to 100% of the maximal force obtained in pCa 4.5. The relationship between the degree of myosin light chain phosphorylation and force was similar in the two types of activation; varied [OA] at constant [Ca2+] and at varied [Ca2+]. The relation between force and Vmax when the degree of activation was altered with OA was almost identical to that obtained with varied [Ca2+]. The results show that Ca2+ and OA do not influence force or Vmax in the maximally phosphorylated state and suggest that the level of myosin light chain phosphorylation is the major factor determining Vmax. The finding that the relationship between force and Vmax was similar when activation was altered with OA and Ca2+ suggests, however, that alterations in the absolute rates of phosphorylation and dephosphorylation at a constant phosphorylation level do not influence the mechanical properties of the skinned smooth muscle fibres.}},
author = {{Malmqvist, Ulf and Arner, A}},
issn = {{0031-6768}},
keywords = {{Okadaic acid; Myosin light chain phosphorylation; Skinned fibres; Force-velocity relation}},
language = {{eng}},
number = {{1-2}},
pages = {{42--48}},
publisher = {{Springer}},
series = {{Pflügers Archiv}},
title = {{Regulation of force and shortening velocity by calcium and myosin phosphorylation in chemically skinned smooth muscle}},
url = {{http://dx.doi.org/10.1007/s004240050246}},
doi = {{10.1007/s004240050246}},
volume = {{433}},
year = {{1996}},
}