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

Abstract

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 mᴍ, the membrane displays a near zero voltage, whereas 2 mᴍ ATP will hyper-polarize 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 Together with previous work on a tonoplast vesicle preparation and unpublished data on vacuoles from our laboratory, the present results indicate an electrogenic membrane ATPase pumping protons from the cytoplasm to the vacuole.