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Effects of calcium and substrate on force-velocity relation and energy turnover in skinned smooth muscle of the guinea-pig

Arner, Anders LU and Hellstrand, Per LU (1985) In Journal of Physiology 360. p.347-365
Abstract
Mechanical properties and rate of ATP breakdown (JATP) have been determined in the chemically skinned guinea-pig taenia coli at 22 degrees C. The influence of varied [Ca2+], [Mg ATP] and muscle length were investigated. The shortening response after a step decrease in force (isotonic quick release) was highly curvilinear in the first 100-200 ms. This effect was shown to be a time-dependent response to the force step and not primarily caused by the shift along the length-force relation associated with shortening. Maximal shortening velocity (Vmax) decreased gradually following the release. At pCa (= -log [Ca2+]) 4.5, Vmax at 20 and 1000 ms after release was 0.49 +/- 0.07 and 0.041 +/- 0.004 (mean +/- S.E. of mean, n = 5) lengths s-1... (More)
Mechanical properties and rate of ATP breakdown (JATP) have been determined in the chemically skinned guinea-pig taenia coli at 22 degrees C. The influence of varied [Ca2+], [Mg ATP] and muscle length were investigated. The shortening response after a step decrease in force (isotonic quick release) was highly curvilinear in the first 100-200 ms. This effect was shown to be a time-dependent response to the force step and not primarily caused by the shift along the length-force relation associated with shortening. Maximal shortening velocity (Vmax) decreased gradually following the release. At pCa (= -log [Ca2+]) 4.5, Vmax at 20 and 1000 ms after release was 0.49 +/- 0.07 and 0.041 +/- 0.004 (mean +/- S.E. of mean, n = 5) lengths s-1 respectively. Unloaded shortening velocity obtained from length steps of different magnitude (slack test) also showed a gradual decrease after the release, consistent with the isotonic release results. Increasing [Ca2+] from the relaxed state at pCa 9 (1 microM-calmodulin present) gave increased isometric force to a maximum at pCa 4.5. Half-maximal response was obtained at pCa 6.1. JATP at maximal force at pCa 4.5 was about 3 times the basal rate at pCa 9. The relation between JATP and force was highly non-linear, with a marked increase in JATP with little alteration in force at the highest [Ca2+]. When force was reduced to zero at pCa 4.5 by shortening the muscle to 0.3 L0 (L0 being the length giving maximal active force), JATP decreased by about 30%. At two levels of [Ca2+] giving similar force (pCa 5.75 and 4.5) the energetic tension cost obtained by length variations was lower at the low [Ca2+]. At pCa 6.0, Vmax and force were decreased to the same extent relative to their values at pCa 4.5. At pCa 5.75, where there was no reduction in force but a 25% decrease in isometric JATP, Vmax was unchanged relative to pCa 4.5. Force, Vmax and JATP were all dependent on [Mg ATP]. Half-maximal response was obtained at 0.1 mM for force and Vmax, and at 0.5 mM for JATP. The results are discussed in relation to a possible influence of both Ca2+ and Mg ATP on kinetic properties of the cross-bridge cycle. (Less)
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published
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in
Journal of Physiology
volume
360
pages
347 - 365
publisher
The Physiological Society
external identifiers
  • pmid:3872937
  • scopus:0022034172
ISSN
1469-7793
language
English
LU publication?
yes
id
883e06a5-e50f-4dc0-9a75-7d785f2e0d55 (old id 1103438)
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http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1193465&blobtype=pdf
date added to LUP
2008-08-11 13:56:09
date last changed
2017-08-06 04:24:17
@article{883e06a5-e50f-4dc0-9a75-7d785f2e0d55,
  abstract     = {Mechanical properties and rate of ATP breakdown (JATP) have been determined in the chemically skinned guinea-pig taenia coli at 22 degrees C. The influence of varied [Ca2+], [Mg ATP] and muscle length were investigated. The shortening response after a step decrease in force (isotonic quick release) was highly curvilinear in the first 100-200 ms. This effect was shown to be a time-dependent response to the force step and not primarily caused by the shift along the length-force relation associated with shortening. Maximal shortening velocity (Vmax) decreased gradually following the release. At pCa (= -log [Ca2+]) 4.5, Vmax at 20 and 1000 ms after release was 0.49 +/- 0.07 and 0.041 +/- 0.004 (mean +/- S.E. of mean, n = 5) lengths s-1 respectively. Unloaded shortening velocity obtained from length steps of different magnitude (slack test) also showed a gradual decrease after the release, consistent with the isotonic release results. Increasing [Ca2+] from the relaxed state at pCa 9 (1 microM-calmodulin present) gave increased isometric force to a maximum at pCa 4.5. Half-maximal response was obtained at pCa 6.1. JATP at maximal force at pCa 4.5 was about 3 times the basal rate at pCa 9. The relation between JATP and force was highly non-linear, with a marked increase in JATP with little alteration in force at the highest [Ca2+]. When force was reduced to zero at pCa 4.5 by shortening the muscle to 0.3 L0 (L0 being the length giving maximal active force), JATP decreased by about 30%. At two levels of [Ca2+] giving similar force (pCa 5.75 and 4.5) the energetic tension cost obtained by length variations was lower at the low [Ca2+]. At pCa 6.0, Vmax and force were decreased to the same extent relative to their values at pCa 4.5. At pCa 5.75, where there was no reduction in force but a 25% decrease in isometric JATP, Vmax was unchanged relative to pCa 4.5. Force, Vmax and JATP were all dependent on [Mg ATP]. Half-maximal response was obtained at 0.1 mM for force and Vmax, and at 0.5 mM for JATP. The results are discussed in relation to a possible influence of both Ca2+ and Mg ATP on kinetic properties of the cross-bridge cycle.},
  author       = {Arner, Anders and Hellstrand, Per},
  issn         = {1469-7793},
  language     = {eng},
  pages        = {347--365},
  publisher    = {The Physiological Society},
  series       = {Journal of Physiology},
  title        = {Effects of calcium and substrate on force-velocity relation and energy turnover in skinned smooth muscle of the guinea-pig},
  volume       = {360},
  year         = {1985},
}