[Membrane potential levels in Acetabularia cells].

The membrane potential (MP) of A. mediterranea cell is shown to have two stationary levels RP==--170 mv and EP=--80 mV and an unstable one -- level of action potential peaks -- EP=--60 mV. The following transitions between the MP levels are possible: RP leads to EP' equilibrium EP leads to RP. The transition RP leads to EP' always has an exponential region. Values of the MP levels and the time constant of RP leads to EP' transition are equal in spontaneous AP, in AP induced by switching off the light or current pulse, when the cell is treated with 10(-3) M solution of DNP and when a part of cell is amputated. It is suggested that RP leads to EP' transition takes place when the electrogenic Cl-pump is switched off, while EP leads to RP when it is switched on.