Changes in permeability to protons and other cations at high proton motive force in rat liver mitochondria

Abstract

1. We have confirmed that the respiration rate of rat liver mitochondria can be substantially inhibited with only a small drop in proton motive force. We have directly measured the passive proton permeability as a function of .DELTA..psi. by using K+ diffusion potentials and have shown that there is a large increase in proton permeability at high .DELTA..psi.. This can quantitatively account for the inhibitor titrations of respiration. 2. .DELTA..psi. and .DELTA.pH were shown to have roughly equal effects on the relatively high respiration rate in static head. 3. The permeabilities to K+, tetramethylammonium+ and choline+ were shown to increase greatly at high .DELTA..psi., in a similar way to proton permeability, indicating a similar mechanism of entry.