THE ROLE OF MITOCHONDRIAL POTASSIUM FLUXES IN CONTROLLING THE PROTONMOTIVE FORCE IN ENERGIZED MITOCHONDRIA

The two components of the protonmotive force, the pH gradient (Delta p H) and the transmembrane electric potential (Delta psi), were measured in rat liver mitochondria as a function of K+ concentration in the su spending medium. It was found that both the rate of formation and the final level of Delta pH upon energization of mitochondria with succina te increased with increasing [K+]. Concomitantly, Delta psi decreased so that the level of the protonmotive force remained practically uncha nged. Potassium channel opener RP66471 further potentiated both the fo rmation rate and the level of Delta pH. These results are interpreted as showing that the electrophoretic K+ influx enables the formation of Delta pH by partly compensating charge transfer due to the proton pum ping. (C) 1995 Academic Press, Inc.