A Patch Clamp Study of Tonoplast Electrical Properties in Vacuoles Isolated from Chenopodium rubrum Suspension Cells

Christian Baum ann Physiologisches Institut der Justus-Liebig-Universität Gießen, Aulweg 129, D-6300 Gießen, Bundesrepublik Deutschland Z. Naturforsch. 40c, 886—890 (1985); received October 23, 1985 Patch Clamp, Membrane ATPase, Tonoplast, Vacuole, Chenopodium rubrum L. The patch clamp technique has been applied to isolated vacuoles from green suspension cells of Chenopodium rubrum to record electrical parameters of the tonoplast. In a symmetrical K* solution of 46 mM, the membrane displays a near zero voltage, whereas 2 mM ATP will hyperpolarize it to 15 or 20 mV (vacuole positive). The conductance amounts to about one S-m~2. Fluctuations of the clamp current are explained by an unknown channel species having opening times of 5 — 10 ms. Together with previous work on a tonoplast vesicle preparation and unpub­ lished data on vacuoles from our laboratory, the present results indicate an electrogenic mem­ brane ATPase pumping protons from the cytoplasm to the vacuole.