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>Homeostatic Regulation of Membrane Potential by an Electrogenic Ion Pump against Change in the K+Concentration of the Extra- and Intra-Organ Perfusion Solutions
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Homeostatic Regulation of Membrane Potential by an Electrogenic Ion Pump against Change in the K+Concentration of the Extra- and Intra-Organ Perfusion Solutions
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机译：Homeostatic Regulation of Membrane Potential by an Electrogenic Ion Pump against Change in the K+Concentration of the Extra- and Intra-Organ Perfusion Solutions
The dependence of membrane potentials on changes in the extra-cellular K+concentration K+ewas investigated in potato tuber slices with dripping perfusion, and in growingVignahypocotyl segments with pressurized intra-organ perfusion methods. Only under anoxia were the membrane potential of potato tuber slices and the electric potential difference between the parenchyma symplast and xylem (Vpx) ofVignahypocotyl segments depolarized markedly (46 mV and 42 mV/logK+eunit, respectively) with increasing K+eabove the critical values. The electric potential difference between the parenchyma symplast and organ surface (Vpsof the hypocotyl segments remained nearly unchanged up to 30 mEq K+e. Under highly aerobic conditions the membrane potentials were relatively independent of K+eexcept at very high K+concentrations. Vpsshowed even hyperpolarization with the increasing KCl concentration in the perfusion solution that is not in direct contact with the surface membrane of the parenchyma symplast. The respiration-dependent electrogenic components of the membrane potentials regularly increased with the increasing K+e. A voltage-dependent homeostatic control of membrane potential is discussed.
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