Membrane Potential of Electrolyte-depleted Muscle Fibres

Abstract

Koketsu and Kimura¹ have reported experiments in which the potassium concentration within frog muscle fibres [K]_i was reduced by soaking sartorii in hypotonic sucrose solutions. They found that, although [K]_i was reduced from 130 to about 48 m.equiv./l fibre water by this procedure, the membrane potential of the fibres measured in normal Ringer's fluid by the micro-electrode technique was not decreased. It remained at about 93 mV, in spite of the fact that the potassium-equilibrium potential E_K was then only 80 mV. They concluded that the results did not favour the ionic theory of membrane potential^2–4. Ling also quoted these experiments⁵ as evidence against the membrane theory.