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Histochemistry and Cell Biology

, Volume 111, Issue 2, pp 117–123 | Cite as

Fiber type composition of four hindlimb muscles of adult Fisher 344 rats

  • Robert S. Staron
  • William J. Kraemer
  • Robert S. Hikida
  • Andy C. Fry
  • Jerry D. Murray
  • Gerson E. R. Campos
ORIGINAL PAPER

Abstract

 The limb and trunk muscles of adult rats express four myosin heavy chain (MHC) isoforms, one slow (MHCI) and three fast (MHCIIa, MHCIId, and MHCIIb). The distribution of these isoforms correlates with fiber types delineated using myofibrillar actomyosin adenosine triphosphatase (mATPase) histochemistry. For example, type I fibers express MHCI and fiber types IIA, IID, and IIB express MHCIIa, MHCIId, and MHCIIb, respectively. Fibers containing only one MHC isoform have been termed ”pure” fibers. Recent evidence suggests that a population of ”hybrid” fibers exist in rat skeletal muscle which contain two MHC isoforms. The purpose of the present investigation was to document the entire range of histochemically defined ”pure” and ”hybrid” fiber types in untreated muscles of the young adult Fisher 344 rat hindlimb. The selected hindlimb muscles (soleus, tibialis anterior, extensor digitorum longus, and gastrocnemius muscles) were removed from 12 male rats and analyzed for muscle fiber type distribution, cross-sectional area, and MHC content. Care was taken to delineate eight fiber types (I, IC, IIC, IIA, IIAD, IID, IIDB, and IIB) using refined histochemical techniques. Hybrid fibers were found to make up a considerable portion of the muscles examined (a range of 8.8–17.8% of the total). The deep red portion of the gastrocnemius muscle contained the largest number of hybrid fibers, most of which were the fast types IIAD (8.5±2.8%) and IIDB (5.2±2.3%). In conclusion, hybrid fibers make up a considerable portion of normal rat limb musculature and are an important population that should not be ignored.

Keywords

Fiber Type Myosin Heavy Chain Gastrocnemius Muscle Trunk Muscle Muscle Fiber Type 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Robert S. Staron
    • 1
  • William J. Kraemer
    • 2
  • Robert S. Hikida
    • 1
  • Andy C. Fry
    • 1
  • Jerry D. Murray
    • 1
  • Gerson E. R. Campos
    • 1
  1. 1.Department of Biomedical Sciences, College of Osteopathic Medicine, Ohio University, Irvine Hall, rm 430, Athens, Ohio 45701 e-mail: staron@ohiou.edu Tel. +1-614 593 2409; Fax +1-614 597 2778
  2. 2.Center for Sports Medicine, The Pennsylvania State University, University Park, PA 16802, USAUS

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