Cross-Bridge and Calcium Behavior in Ferret Papillary Muscle in Different Thyroid States

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Author(s)

Abstract

X-ray diffraction studies were made using synchrotron radiation on ferret right ventricular papillary muscle under three different thyroid states: euthyroidism, hyperthyroidism, and hypothyroidism. The latter two states were induced by treatment with L-thyroxine and methimazole, respectively. The X-ray equatorial reflections were recorded at a time resolution of 10 ms to study the mass movement of myosin cross-bridges from thick to thin filaments. The myosin isomer content was measured by gel electrophoresis which showed that V3 isomer was predominant in euthyroid muscle and 27% of myosin was V1 isomer in hyperthyroid muscle. The intracellular free Ca concentration was measured by using the aequorin method. The peak Ca concentration was similar in all three states, but in the hypothyroid state the time-to-peak was longer and the decay was slower. The time-to-peak of twitch tension was shorter in hyperthyroidism and longer in hypothyroidism than in euthyroidism. The different time courses of twitch tension in different thyroid states accompanied a cross-bridge movement which closely followed the tension development. In hyperthyroidism, the cross-bridge movement significantly preceded tension development, suggesting that hyperthyroid myosin (V1) has a longer latency period between the shift to the vicinity of the thin filament and force development.<br>

Journal

  • The Japanese Journal of Physiology

    The Japanese Journal of Physiology 51(3), 319-326, 2001-06

    THE PHYSIOLOGICAL SOCIETY OF JAPAN

References:  22

Codes

  • NII Article ID (NAID)
    10008293731
  • NII NACSIS-CAT ID (NCID)
    AA00691224
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    0021521X
  • NDL Article ID
    5840260
  • NDL Source Classification
    ZS8(科学技術--医学--解剖学・生理学・生化学)
  • NDL Call No.
    Z53-D40
  • Data Source
    CJP  NDL  J-STAGE 
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