イオンchannelの親和性とgating機構の状態の示標
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概要
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A theoretical relation between permeability and the affinity of channels specific for the questioned ion species was derived in terms of the fluid mosaic model. It was mentioned that, when the affinity of channels to the permeable ion was not extremely high, the dependence of the chord conductance on membrance potential did not correctly represent the dependecne of the number of the conducting channels on membrane potential. Analyses of the relation of K permeability to [K]<SUB>0</SUB> in Nitella and myelinated nerve fibres revealed that the affinity of K channels was independent of membrane potential, and neither so high that all the conducting channels were occupied by K<SUP>+</SUP>, nor so low that only a negligible fraction of the channels was occupied. Under such conditions, the actual relation of the number of open K channels to membrane potential may be estimated from the modified g<SUB>K</SUB> vs. E relation obtained by using the instantaneous current voltage relation.