This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.104.041483v1 88/3/2340    most recent Alert me when this article is cited Alert me if a correction is posted Services 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 Google Scholar Google Scholar Articles by Hattori, T. Articles by Ohta, Y. Search for Related Content PubMed PubMed Citation Articles by Hattori, T. Articles by Ohta, Y.

Repetitive Transient Depolarizations of the Inner Mitochondrial Membrane Induced by Proton Pumping

Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Nakacho, Koganei, Tokyo 184-8588, Japan

Correspondence: Address reprint requests to Yoshihiro Ohta, E-mail: ohta{at}cc.tuat.ac.jp.

Single mitochondria show the spontaneous fluctuations of m. In this study, to examine the mechanism of the fluctuations, we observed m in single isolated heart mitochondria using time-resolved fluorescence microscopy. Addition of malate, succinate, or ascorbate plus TMPD to mitochondria induced polarization of the inner membrane followed by repeated cycles of rapid depolarizations and immediate repolarizations. ADP significantly decreased the frequency of the rapid depolarizations, but the ADP effect was counteracted by oligomycin. On the other hand, the rapid depolarizations did not occur when mitochondria were polarized by the efflux of K⁺ from the matrix. The rapid depolarizations became frequent with the increase in the substrate concentration or pH of the buffer. These results suggest that the rapid depolarizations depend on the net translocation of protons from the matrix. The frequency of the rapid depolarizations was not affected by ROS scavengers, Ca²⁺, CsA, or BA. In addition, the obvious increase in the permeability of the inner membrane to calcein (MW 623) that was entrapped in the matrix was not observed upon the transient depolarization. The mechanisms of the spontaneous oscillations of m are discussed in relation to the matrix pH and the permeability transitions.