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Myosin composition and functional properties of smooth muscle from the uterus of pregnant and non-pregnant rats

Sparrow, Malcolm P; Mohammad, Mukhallad A; Arner, Anders LU ; Hellstrand, Per LU and Ruegg, J Caspar (1988) In Pflügers Archiv 412(6). p.624-633
Abstract
The myosin heavy chain stoichiometry and the force-velocity relation have been determined in the myometrium of the non-pregnant and pregnant rat. The relative proportions of the slower migrating heavy chain (MHC1) greatly exceeded that of the faster migrating heavy chain (MHC2) as shown by electrophoresis on SDS 4%-polyacrylamide gels. The ratios of MHC1/MHC2 were 2.2/1 in the non-pregnant rats, 2.6/1 in the pregnant rat, and contrasted with 0.8/1 in the rat portal vein. This stoichiometry was unchanged by extracting the myosin from the smooth muscle as native myosin in a salt extract, as dissociated myosin using sodium dodecyl sulphate (SDS) or by isolating the native myosin first by a non-dissociating (pyrophosphate) electrophoresis step... (More)
The myosin heavy chain stoichiometry and the force-velocity relation have been determined in the myometrium of the non-pregnant and pregnant rat. The relative proportions of the slower migrating heavy chain (MHC1) greatly exceeded that of the faster migrating heavy chain (MHC2) as shown by electrophoresis on SDS 4%-polyacrylamide gels. The ratios of MHC1/MHC2 were 2.2/1 in the non-pregnant rats, 2.6/1 in the pregnant rat, and contrasted with 0.8/1 in the rat portal vein. This stoichiometry was unchanged by extracting the myosin from the smooth muscle as native myosin in a salt extract, as dissociated myosin using sodium dodecyl sulphate (SDS) or by isolating the native myosin first by a non-dissociating (pyrophosphate) electrophoresis step and subsequently analysing the protein bands on the SDS 4%-polyacrylamide gel. Although the unequal proportions of the heavy chains suggested the possibility that the native myosin molecule may be arranged as homodimeric heavy chains, no evidence for or against the existence of native myosin isoforms could be obtained by electrophoresing native myosin extracts on pyrophosphate-polyacrylamide gels. The force-velocity relations of the intact electrically stimulated myometrium from the non-pregnant and pregnant rats gave isometric force of 45 and 135 mN/mm2 and Vmax of 0.71 and 0.52 lengths/s (37 degrees C) when measured at 95% of optimal length, whereas in chemically skinned uterine strips at 22 degrees C Vmax was 0.09 and 0.13 lengths/s, respectively. The length-force relationship was of similar shape in the non-gravid and gravid skinned tissues. The energetic tension cost (ATP-turnover/active stress) in skinned fibres was also similar. The mechanical and metabolic characteristics of the gravid and non-gravid uterus found in the present study do not suggest an obvious difference in the intrinsic properties of the myosin, although significant functional alterations in the tissue appear during pregnancy. This corresponds to the lack of a difference in the pattern of the heavy chains. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Smooth muscle, Myosin isozymes, Pyrophosphate gels, Uterus, Pregnancy
in
Pflügers Archiv
volume
412
issue
6
pages
624 - 633
publisher
Springer
external identifiers
  • pmid:3211713
  • scopus:0023690482
ISSN
0031-6768
DOI
10.1007/BF00583764
language
English
LU publication?
yes
id
4c9b65e3-a28f-46ea-b595-7241b6e36403 (old id 1104238)
date added to LUP
2008-08-07 13:06:45
date last changed
2017-08-06 04:36:52
@article{4c9b65e3-a28f-46ea-b595-7241b6e36403,
  abstract     = {The myosin heavy chain stoichiometry and the force-velocity relation have been determined in the myometrium of the non-pregnant and pregnant rat. The relative proportions of the slower migrating heavy chain (MHC1) greatly exceeded that of the faster migrating heavy chain (MHC2) as shown by electrophoresis on SDS 4%-polyacrylamide gels. The ratios of MHC1/MHC2 were 2.2/1 in the non-pregnant rats, 2.6/1 in the pregnant rat, and contrasted with 0.8/1 in the rat portal vein. This stoichiometry was unchanged by extracting the myosin from the smooth muscle as native myosin in a salt extract, as dissociated myosin using sodium dodecyl sulphate (SDS) or by isolating the native myosin first by a non-dissociating (pyrophosphate) electrophoresis step and subsequently analysing the protein bands on the SDS 4%-polyacrylamide gel. Although the unequal proportions of the heavy chains suggested the possibility that the native myosin molecule may be arranged as homodimeric heavy chains, no evidence for or against the existence of native myosin isoforms could be obtained by electrophoresing native myosin extracts on pyrophosphate-polyacrylamide gels. The force-velocity relations of the intact electrically stimulated myometrium from the non-pregnant and pregnant rats gave isometric force of 45 and 135 mN/mm2 and Vmax of 0.71 and 0.52 lengths/s (37 degrees C) when measured at 95% of optimal length, whereas in chemically skinned uterine strips at 22 degrees C Vmax was 0.09 and 0.13 lengths/s, respectively. The length-force relationship was of similar shape in the non-gravid and gravid skinned tissues. The energetic tension cost (ATP-turnover/active stress) in skinned fibres was also similar. The mechanical and metabolic characteristics of the gravid and non-gravid uterus found in the present study do not suggest an obvious difference in the intrinsic properties of the myosin, although significant functional alterations in the tissue appear during pregnancy. This corresponds to the lack of a difference in the pattern of the heavy chains.},
  author       = {Sparrow, Malcolm P and Mohammad, Mukhallad A and Arner, Anders and Hellstrand, Per and Ruegg, J Caspar},
  issn         = {0031-6768},
  keyword      = {Smooth muscle,Myosin isozymes,Pyrophosphate gels,Uterus,Pregnancy},
  language     = {eng},
  number       = {6},
  pages        = {624--633},
  publisher    = {Springer},
  series       = {Pflügers Archiv},
  title        = {Myosin composition and functional properties of smooth muscle from the uterus of pregnant and non-pregnant rats},
  url          = {http://dx.doi.org/10.1007/BF00583764},
  volume       = {412},
  year         = {1988},
}