Ion Transport in Liver Mitochondria. V. The Effect of Anions on the Mechanism of Aerobic K⁺ Uptake^*

Abstract

The effect of succinate on the stoichiometry of proton translocation and on mitochondrial swelling during K4 uptake has been studied. The decrease of the H4 :K4 ratio from 1 to 0.2 is accounted for quantitatively by the intramitochondrial accumulation of succinate.When the accumulation of succinate is inhibited at alkaline pH the H4:K4 ratio increases.

Phosphate-induced Stimulation of Acceptorless Respiration in Corn Mitochondria

“…They differ in two respects: acceptorless respiration was lower in fresh mitochondria and there was a burst of respiration on addition of ADP, just as reported for liver mitochondria (9,23). With the aged mitochondria there was no respiratory burst.…”

“…However, there is only trivial swelling until Pi is added. In liver mitochondria, release of respiration by valinomycin in the absence of Pi or acetate is linked to substrate uptake, for example succinate (23). Using NADH as substrate in corn mitochondria shows that valinomycin can act much like an uncoupler in the absence of permeant anions or substrates; i.e., facilitating membrane penetration by K+ releases respiration by a means not linked to net salt transport.…”

Mitochondria metabolite transport

“…The uptake of succinate has been measured in as-sociation with movement of Ca2+ and K+ [2 1, 22,34] . Furthermore, the rate of succinate oxidation could be quantitatively correlated to succinate uptake which controls the internal succinate concentration [35].…”

Calcium ion-induced uptakes and transformations of substrates in liver mitochondria

“…Along with a net gain of cations there is in general a less-thanequivalent loss of protons; electroneutrality is maintained by anion uptake. When there is a massive uptake of K+, a considerable quantity of anions also moves (Lynn & Brown, 1966; , although there is also a variable amount of ejection of protons (Harris, Cockrell & Pressman, 1966;Rossi, Scarpa & Azzone, 1967). Ca2+ uptake, which requires energy but no special inducing agent, has been noted to be accompanied by uptake of phosphate (Lehninger, Rossi & Greenawalt, 1963), acetate (Rasmussen, Chance & Ogata, 1965), malate (Quagliariello & Palmieri, 1969), glutamate or hydroxybutyrate (Kimmich & Rasmussen, 1968).…”