Oscillation of membrane potential in L cells: III. K+ current-voltage curves

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Abstract
Cultured L cells were found previously to have an oscillating membrane potential. Current-voltage (I–V) curves were measured during these oscillations. TwoI–V curves were recorded, one at the maximum and one at the minimum of oscillations. Each curve is nonlinear, and when they are subtracted from one another, the result gives theI–V curve for the K+ current producing oscillations. ThisI K–V curve is zero for −85 to −90mV and saturates for positive and high negative membrane potentials. When the external K+ is increased theI–V curve is shifted and its zero current potential is reduced. The K+ zero current potential follows a Nernst relation when plotted against the external K+ concentration. TheI K–V curves all have a similar shape at different K+ concentrations, showing a saturation on each side of the zero current potential. The results can be explained satisfactorily in term of a carrier model for K+ ions.