Work-induced growth of rat soleus muscle is accompanied by an early increase in new RNA synthesis. To determine the cell type(s) responsible for the increased RNA synthesis, we compared light autoradiographs of control and hypertrophying muscles from rats injected with tritiated uridine 12, 24, and 48 h after inducing hypertrophy. There was an increased number of silver grains over autoradiographs of hypertrophied muscle. This increase occurred over connective tissue cells; there was no increase in the number of silver grains over the muscle fibers. Quantitative studies demonstrated that between 70 and 80% of the radioactivity in the muscle that survived fixation and washing was in RNA. Pretreatment of the animals with actinomycin D reduced in parallel both the radioactivity in RNA and the number of silver grains over autoradiographs. Proliferation of the connective tissue in hypertrophying muscle was evident in light micrographs, and electron micrographs identified the proliferating cells as enlarged fibroblasts and macrophages; the connective tissue cells remained after hypertrophy was completed. Thus, proliferating connective tissue cells are the major site of the increase in new RNA synthesis during acute work-induced growth of skeletal muscle. It is suggested that in the analysis of physiological adaptations of muscle, the connective tissue cells deserve consideration as a site of significant molecular activity.
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1 June 1973
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June 01 1973
AUTORADIOGRAPHIC LOCALIZATION OF NEW RNA SYNTHESIS IN HYPERTROPHYING SKELETAL MUSCLE
Charles K. Jablecki,
Charles K. Jablecki
From the Laboratory of Neurochemistry, National Institute of Mental Health, and the Laboratory of Neuropathology and Neuroanatomical Sciences, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20014.
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John E. Heuser,
John E. Heuser
From the Laboratory of Neurochemistry, National Institute of Mental Health, and the Laboratory of Neuropathology and Neuroanatomical Sciences, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20014.
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Seymour Kaufman
Seymour Kaufman
From the Laboratory of Neurochemistry, National Institute of Mental Health, and the Laboratory of Neuropathology and Neuroanatomical Sciences, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20014.
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Charles K. Jablecki
From the Laboratory of Neurochemistry, National Institute of Mental Health, and the Laboratory of Neuropathology and Neuroanatomical Sciences, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20014.
John E. Heuser
From the Laboratory of Neurochemistry, National Institute of Mental Health, and the Laboratory of Neuropathology and Neuroanatomical Sciences, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20014.
Seymour Kaufman
From the Laboratory of Neurochemistry, National Institute of Mental Health, and the Laboratory of Neuropathology and Neuroanatomical Sciences, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20014.
Dr. Jablecki's present address is the Department of Neurology, Mayo Clinic, Rochester, Minnesota 55901. Dr. Heuser's present address is the Department of Biophysics, University College of London, London WC 1, England.
Received:
October 19 1972
Revision Received:
February 05 1973
Online ISSN: 1540-8140
Print ISSN: 0021-9525
Copyright © 1973 by The Rockefeller University Press
1973
J Cell Biol (1973) 57 (3): 743–759.
Article history
Received:
October 19 1972
Revision Received:
February 05 1973
Citation
Charles K. Jablecki, John E. Heuser, Seymour Kaufman; AUTORADIOGRAPHIC LOCALIZATION OF NEW RNA SYNTHESIS IN HYPERTROPHYING SKELETAL MUSCLE . J Cell Biol 1 June 1973; 57 (3): 743–759. doi: https://doi.org/10.1083/jcb.57.3.743
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