Separate Oscillations of the Electrogenic Pump and of a K+ -Channel in Nitella as Revealed by Simultaneous Measurement of Membrane Potential and of Resistance

In Nitella oscillations of membrane potential with periods ofabout 15 min and of about 1 h can be observed. The comparisonof the related changes in resistance and in potential showsthat the 1-h oscillation controls a carrier-type transporter,probably an electrogenic pump with a stoichiometry of 1 H⁺/1ATP. The control loop related to the 1-h oscillation can bestimulated by internal pH as changed by butyrate or procaine.IV-curve studies show that the 15-min oscillation modulatesthe conductivity of a K⁺ -channel. No way has been found toinfluence the spontaneously occurring 15-min oscillation whichprobably is generated in the chioroplasts. The oscillationsseem to provide a means of exerting a selective influence onone transporter. Correspondence to: Institut für Angewandte Physik, NeueUniversität, Haus N61A, D-2300 Kiel, F.R.G. Key words: H⁺-pump, IV-curves, Nitella, oscillations, pH-regulation, potassium channel, stoichiometry