CATION UPTAKE AS BASIS FOR PRODUCTION OF PROTON PULSES BY MITOCHONDRIA AT ANAEROBIC-AEROBIC TRANSITION

Calcium movement and proton pulse production by mitochondria have been studied using pH‐ and K+‐sensitive glass electrodes and the Ca++ indicator murexide. Anaerobic treatment led to the release of free Ca++ into the medium, the quantity depending on the preparative procedure and the composition of the medium. The ejection of protons by anaerobic mitochondria given small additions of oxygen was accompanied by the uptake of approximately equal numbers of calcium ions. Addition of ethylene glycol bis (β‐aminoethyl)‐N, N′‐tetraacetic acid (EGTA) reduced the proton pulses to about 40% of their maximum size in KCl medium, and to 5% in a sucrose medium. Mitochondria treated with EGTA and valinomycin gave proton pulses that were accompanied by approximately equal uptakes of K+. Mitochondria kept anaerobic for 20 min and then aerated were found to be without respiratory control by ADP unless EGTA was added before aeration. It is concluded that the production of proton pulses by untreated mitochondria at the anaerobic‐aerobic transition occurs only under conditions where sufficient free Ca++ has leaked out to allow energy‐dependent exchange between external Ca++ and internal protons. Copyright © 1969, Wiley Blackwell. All rights reserved