This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Lassalles, J.-P. Articles by Thellier, M. Search for Related Content PubMed PubMed Citation Articles by Lassalles, J.-P. Articles by Thellier, M. Agricola Articles by Lassalles, J.-P. Articles by Thellier, M.

Membranes and Bioenergetics

Microelectrode Measurements on Red Beet Vacuole ¹

Biological Effect of Na⁺ OR NO₃^– Ions, Diffusing from the Microelectrode

Laboratoire "Echanges cellulaires", UA CNRS 203, Faculté des Sciences, BP 67, F76130 Mont-Saint-Aignan, France

Glass microelectrodes filled with 3 molar KCl are widely used to measure intracellular potentials and it is usual to try to minimize their electrolyte loss. In these experiments we have used the ionic leak of our microelectrodes, filled with various salt solutions, to introduce a given ion into the red beet vacuole. This allowed us to show that NO₃^– ions reduce the magnitude of the current spectral density while they do not change the resistance of the tonoplast. This is true when NO₃^– is either added to the external medium or used as the microelectrode filling solution. This can be interpreted by a NO₃^– effect on the vacuolar side of the tonoplast, resulting in an inhibition of the ion transporting ATPase. Replacing K⁺ by Na⁺ ions in the medium has no effect on tonoplast resistance (R_s). On the contrary, when ions leaking from the microelectrode are H⁺, Li⁺ or K⁺, R_s is close to 4 kilohm square centimeter, whereas R_s is of the order of 30K square centimeter when Na⁺ are the leaking ions. We also found a possible correlation between the presence of a Lorentzian in the current spectral density (cut-off frequency = 2 hertz) and a Cl^– efflux from the vacuole. This could be explained by the existence of Cl^– channels on the tonoplast.