Cell and Tissue Research

, Volume 275, Issue 1, pp 39-49

Cytoplasm-to-myonucleus ratios and succinate dehydrogenase activities in adult rat slow and fast muscle fibers

  • Brian S. TsengAffiliated withDepartment of Physiological Science, University of California
  • , Christine E. KasperAffiliated withSchool of Nursing
  • , V. Reggie EdgertonAffiliated withDepartment of Physiological Science, University of California

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The relationship between myonuclear number, cellular size, succinate dehydrogenase activity, and myosin type was examined in single fiber segments (n=54; 9±3 mm long) mechanically dissected from soleus and plantaris muscles of adult rats. One end of each fiber segment was stained for DNA before quantitative photometric analysis of succinate dehydrogenase activity; the other end was double immunolabelled with fast and slow myosin heavy chain monoclonal antibodies. Mean±S.D. cytoplasmic volume/myonucleus ratio was higher in fast and slow plantaris fibers (112±69 vs. 34±21x103 μm3) than fast and slow soleus fibers (40±20 vs. 30±14x103 μm3), respectively. Slow fibers always had small volumes/myonucleus, regardless of fiber diameter, succinate dehydrogenase activity, or muscle of origin. In contrast, smaller diameter (<70 μm) fast soleus and plantaris fibers with high succinate dehydrogenase activity appeared to have low volumes/myonucleus while larger diameter (>70 μm) fast fibers with low succinate dehydrogenase activity always had large volume/myonucleus. Slow soleus fibers had significantly greater numbers of myonuclei/mm than did either fast soleus or fast plantaris fibers (116±51 vs. 55±22 and 44±23), respectively. These data suggest that the myonuclear domain is more limited in slow than fast fibers and in the fibers with a high, compared to a low, oxidative metabolic capability.

Key words

Nucleus DNA Muscle cells Myosin Immunofluorescence microscopy Rat-(Sprague Dawley)