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Myosin light chain phosphorylation and the cross-bridge cycle at low substrate concentration in chemically skinned guinea pig Taenia coli

Hellstrand, Per (author)
Lund University,Lunds universitet,Kärlfysiologi,Forskargrupper vid Lunds universitet,Vascular Physiology,Lund University Research Groups
Arner, Anders (author)
Lund University,Lunds universitet,Kärlfysiologi,Forskargrupper vid Lunds universitet,Vascular Physiology,Lund University Research Groups
 (creator_code:org_t)
1985
1985
English.
In: Pflügers Archiv. - 0031-6768. ; 405:4, s. 323-328
  • Journal article (peer-reviewed)
Abstract Subject headings
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  • Force-velocity relations, rate of ATP turnover (JATP), and phosphorylation of the 20,000 D myosin light chains (LC20) were measured in chemically skinned guinea pig Taenia coli. Relative LC20 phosphorylation at 3.2 mM MgATP was 17% in relaxed tissues at pCa 9, and increased with force at increasing [Ca2+] to a maximum of 67% at pCa 4.5. Force at pCa 4.5 was dependent on the MgATP concentration with a half-maximal response at about 0.1 mM. At 0.1 mM MgATP LC20 phosphorylation at pCa 4.5 was 38%. Both JATP and the maximal shortening velocity (Vmax) were reduced in 0.1 mM MgATP, to 32% and 43%, respectively, of their values at 3.2 mM MgATP. Low-MgATP thus inhibits both LC20 phosphorylation and the extent and rate of cross-bridge interaction. High levels of LC20 phosphorylation, independent of Ca2+ and MgATP concentrations, were obtained by treatment with ATP-gamma-S. Maximal force at 3.2 mM MgATP after LC20 thiophosphorylation was unchanged, whereas halfmaximal force occurred at 0.065 mM MgATP after thiophosphorylation, compared to 0.13 mM after activation by Ca2+. The contraction in thiophosphorylated preparations at low-MgATP (0.1 mM) was associated with submaximal Vmax (60%) and JATP (27%). The results show that LC20 phosphorylation is correlated with the degree of force development in the Ca2+ activated contraction, both when Ca2+ and MgATP concentrations are varied. The reduced force and rate of crossbridge turnover in low MgATP are however primarily mediated by an influence of MgATP on the cross-bridge cycle, which is separate from the effect on LC20 phosphorylation.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)
MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Physiology (hsv//eng)

Keyword

Smooth muscle
ATP
ATP-gamma-S
Ca2
Force-velocity relation
Energetics

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art (subject category)
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By the author/editor
Hellstrand, Per
Arner, Anders
About the subject
MEDICAL AND HEALTH SCIENCES
MEDICAL AND HEAL ...
and Basic Medicine
and Physiology
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Pflügers Archiv
By the university
Lund University

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