Chloride ions and the membrane potential of Purkinje fibres

According to the ionic theory of electrical activity the membrane potential depends on the unequal distribution of ions between the intraand extracellular phases, and on the relative permeability of the membrane towards them. For cardiac muscle the role played by sodium and potassium has been studied to some extent (see Hoffman & Cranefield, 1960) but that of chloride has received little attention. The present paper deals with the effects produced by the substitution for chloride ions of nitrate ions or large anions such as acetylglycinate and pyroglutamate. The results suggest that the contribution of chloride ions to the total membrane conductance is low in a resting fibre but increases when a fibre is depolarized. The findings and interpretations are in good agreement with those recently published by Hutter & Noble (1959). The main results of the present investigation have been reported in a preliminary communication (Carmeliet, 1959). METEODS

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