Electrogenic Pump Current and ATP-Dependent H^+ Efflux Across the Plasma Membrane of Nitellopsis obtusa

元データ 日本植物生理学会


The correlation between the pump current and the ATP-dependent H^+ efflux was examined in internodal cells of Nitellopsis obtusa. To control the cytoplasmic pH and ATP concentration, the tonoplast was removed by intracellular perfusion with an EGTA-containing medium. Two groups of perfused cells were prepared, one with 1 mM ATP (+ATP cells) and the other without ATP but with hexokinase and glucose (-ATP cells). The ATP-dependent H^+ efflux was calculated as the difference in H^+ efflux between the +ATP and -ATP cells. Based on an electrically equivalent circuit model of the plasma membrane, the pump current was calculated from the membrane potentials and the membrane resistances of both +ATP and -ATP cells. When the membrane potential was not too high (-220mV), the ATP-dependent H^+ current (19mA m^<-2>) was almost equal to the pump current (20mA m^<-2>) calculated from the electrical data. This indicates that the electrogenic pump current across the plasma membrane of Nitellopsis obtusa was mostly carried by H^+. But when the membrane potential was high (-280mV), the H^+ current was lower than the pump current. The possible cause of this discrepancy is discussed.


新免 輝男 Department Of Life Science Faculty Of Science Himeji Institute Of Technology
Tazawa M Fukui Univ. Technol. Fukui Jpn
Takeshige K Kyowa Hakko Kogyo Co. Ltd. Tokyo
Shimmen Teruo Department Of Biology Faculty Of Science Osaka University:(present)department Of Botany Faculty Of S
Tazawa Masashi Departlnent Of Biology Faculty Of Science Osaka University
Takeshige Kazuhiko Department of Botany, Faculty of Science, University of Tokyo