The relationship between the H+ and K+ movement across the mitochondrial membrane and the distribution of anions between the intra- and extramitochondrial space has been analyzed in the presence of uncouplers, nigericin and nonactin.
- 1Mitochondria accumulate added anions in the presence of respiratory inhibitors and oligomycin. This accumulation is accompanied by the exit of endogenous anions. Respiration or ATP hydrolysis does not, in itself, increase anion accumulation, but only in as much as it gives rise to proton ejection and cation uptake.
- 2In sucrose medium anion uptake, found in the presence of respiratory inhibitors and oligomycin, is inhibited by uncouplers, nigericin and nonactin, all of which cause H+ uptake and K+ release. The ratio of the intra- to the extramitochondrial concentration of endogenous anions is also strongly diminished by uncouplers, nigericin and nonactin.
- 3With nonactin-pretreated mitochondria, uncouplers, even at very high concentrations, do not inhibit anion uptake.
- 4With nonactin, as the external K+ concentration is increased, the uptake of H+ is progressively decreased and similarly the anion uptake inhibition is diminished.
- 5The 2,4-dinitrophenol-induced uptake of H+ is unaffected by the presence of K+ in the medium up to a concentration of 125 mM. The inhibition of anion uptake and the efflux of endogenous anions, induced by dinitrophenol, are equal in the presence or absence of 100 mM KCl.
- 6In the presence of an external concentration of 100 mM KCl, with nigericin the uptake of H+ is strongly diminished and similarly the anion uptake inhibition and the efflux of endogenous anions are greatly decreased. With nonactin, H+ ejection occurs accompanied by stimulation of anion uptake.
- 7The ratio of the intra- to the extramitochondrial concentration of succinate increases as the external pH decreases. This increase of anion uptake by lowering the pH is inhibited by dinitrophenol.
- 8It is concluded that inhibition of anion uptake and efflux of endogenous anions are dependent upon the uptake of H+ by the mitochondria and vice versa H+ ejection is responsible for stimulation of anion uptake.
proton activity in the inner mitochondrial phase
proton activity in the outer mitochondrial phase