The Mechanism of Ca2+ Action on the Healing-over Process in Mammalian Cardiac Muscles:A Kinetic Analysis

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  • 西江 弘
    Department of Physiology, Faculty of Medicine, University of Tokyo

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タイトル別名
  • THE MECHANISM OF Ca<SUP>2+</SUP> ACTION ON THE HEALINGOVER PROCESS IN MAMMALIAN CARDIAC MUSCLES: A KINETIC ANALYSIS
  • Mechanism of Ca2 + Action on the Healin

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The effect of Ca2+ concentration and temperature on the recovery of membrane potential after investigating lesions using sucrosegap technique in the guinea-pig papillary muscles were studied. At certain temperatures, this recovery showed increased accerelation with increasing Ca2+ concentration. The relation between rate constant of the recovery and Ca2+ concentration was quite similar to that of the reaction between an enzyme and substrate. This relationship could be expressed by the equation Y=xn/(Km+xn), where Y is the normalized rate constant and x the Ca2+ concentration. The coefficient, n, was evaluated by performing Hill's plot. The value of n largely changed between 1 and ca.2 at 32°C-37°C. The input resistance fell at the instant of formation of a lesion and started to rise with recovery of membrane potential. The resistance change after lesion formation was also observed in the potassium-Tyrode's solution in which Na+ was substituted with K+. The concentration-rate relationship of Ca2+ in the healing-over seems to indicate that Ca2+ binds to some molecules in the junctional membrane and produce a structural change of intercalated disc which brings about the healing-over. The large change of n suggests that Ca2+ has a cooperative action in the healing-over process, or alternatively that the state of membrane lipids has some effect on the process.

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