The coupling of electrical ion fluxes in rat liver mitochondria

Abstract

Although the molecular mechanism of the mitochondrial proton pump is not understood [ 11, the ion fluxes driven by the proton pump are phenomenologically distinguished into two groups: (a) the electrical fluxes, whereby strong acids and bases come into equilibrium with A$ and (b) the electroneutral fluxes whereby weak acids and bases come into equilibrium with ApH [2]. Two questions arise. First, this scheme has difficulties to cope with the observation that intact mitochondria catalyze both the active uptake and extrusion of strong electrolytes (i.e. KCl) without inversion of the membrane polarity [3,4]. Second, the notation of the fluxes of strong acids and bases as electrical, leaves still open the dilemma as to whether the coupling of the fluxes involve long range or short range interactions (delocalized or localized potentials). We have examined the effect of divalent cation transport inhibitors on the steady state distribution of divalent cations and on the active divalent cation extrusion [S] . The two processes possess properties which can be explained by assuming a tight coupling of the fluxes. The view is therefore discussed that electrical fluxes may be microscopically coupled through short range interactions (localized potentials).