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Cited by 149Muscle Physiology and DisordersCardiomyopathy and Myosin StudiesCardiovascular and exercise physiology

Fiber type populations and Ca2+-activation properties of single fibers in soleus muscles from SHR and WKY rats

Bortolotto, Susan K., Stephenson, D. George, Stephenson, Gabriela M. M.·1999·American Journal of Physiology-Cell Physiology
DOI 10.1152/ajpcell.1999.276.3.c628
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Abstract

Electrophoretic analyses of muscle proteins in whole muscle homogenates and single muscle fiber segments were used to examine myosin heavy chain (MHC) and myosin light chain 2 (MLC2) isoform composition and fiber type populations in soleus muscles from spontaneously hypertensive rats (SHRs) and their age-matched normotensive controls [Wistar-Kyoto (WKY) rats], at three stages in the development of high blood pressure (4 wk, 16 wk, and 24 wk of age). Demembranated (chemically skinned with 2% Triton X-100), single fiber preparations were used to determine the maximum Ca 2+-activated force per cross-sectional area, calcium sensitivity, and degree of cooperativity of the contractile apparatus and Ca 2+-regulatory system with respect to Ca 2+. The results show that, at all ages examined, 1) SHR soleus contained a lower proportion of MHCI and MLC2 slow (MLC2s) and a higher proportion of MHCIIa, MHCIId/x, and MLC2 fast (MLC2f ) isoforms than the age-matched controls; 2) random dissection of single fibers from SHR and WKY soleus produced four populations of fibers: type I (expressing MHCI), type IIA (expressing MHCIIa), hybrid type I+IIA (coexpressing MHCI and MHCIIa), and hybrid type IIA+IID (coexpressing MHCIIa and MHCIId/x); and 3) single fiber dissection from SHR soleus yielded a lower proportion of type I fibers, a higher proportion of fast-twitch fibers (types IIA and IIA+IID), and a higher proportion of hybrid fibers (types I+IIA and IIA+IID) than the homologous muscles from the age-matched WKY rats. Because the presence of hybrid fibers is viewed as a marker of muscle transformation, these data suggest that SHR soleus undergoes transformation well into adulthood. Our data show also that, for a given fiber type, there are no significant differences between SHR and WKY soleus muscles with respect to any of the Ca 2+-activation properties examined. This finding indicates that the lower specific tensions reported in the literature for SHR soleus muscles are not due to strain- or hypertension-related differences in the function of the contractile apparatus or regulatory system.

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Crossref · 10.1152/ajpcell.1999.276.3.c628

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  • Essential amino acids drive the process of muscle protein synthesis.

    “It has become apparent that it is mainly the essential amino acids that drive the process of muscle protein synthesis [86].”

    From Periodized Nutrition for Athletes (2017) · cites this paper as [86]

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Authors
Bortolotto, S. K., Stephenson, D. G., & Stephenson, G. M. M.
Affiliations
  • Victoria University (AU)
  • La Trobe University (AU)
ORCID
Stephenson, D. George
Venue
American Journal of Physiology-Cell Physiology
Publisher
American Physiological Society
Published
1999-03-01
Volume
276
Issue
3
Pages
C628-C637
ISSN
  • 0363-6143 (ISSN-L)
  • 1522-1563
DOI
10.1152/ajpcell.1999.276.3.c628
OpenAlex
W2182519137
Cited by
149
References
29
Citations by year
2025: 1 · 2024: 1 · 2023: 3 · 2021: 1 · 2020: 3 · 2019: 3 · 2018: 5 · 2017: 3 · 2016: 3 · 2015: 3 · 2014: 9 · 2013: 9 · 2012: 11
FWCI
2.28
Type
journal article
Language
en
Open access
closed
Locations
  • American Journal of Physiology-Cell Physiology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Muscle Physiology and Disorders
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Cardiomyopathy and Myosin Studies
  • Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
Keywords
soleus muscle, spontaneously hypertensive rats, hypertension, muscle fiber composition, myosin heavy chain isoforms, hybrid muscle fibers, calcium activation, calcium sensitivity, contractile apparatus, type I muscle fibers, type IIA fibers
MeSH terms
Animals, Calcium, Isomerism, Male, Muscle Contraction, Rats, Inbred SHR, Rats, Inbred WKY, Muscle, Skeletal, Muscle Fibers, Skeletal, Myosin Light Chains, Myosin Heavy Chains, Rats

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