[Active transport of triphenylmethylphosphonium in mitochondria].

Energy-dependent accumulation of triphenylmethylphosphonium (TPMP+) in rat liver mitochondria at 0 degree C is only 30-50% less than that observed at room temperature, while the rate of TPMP+ penetration drastically decreases enabling accurate studying of transport kinetics. Potassium diffusion potential accelerates the influx of TPMP+ and decreases the efflux rate in agreement with the expected behaviour of penetrating cations diffusing along or against an electric field. On the contrary, energization of mitochondria supposed to generate the metabolic membrane potential increases only the influx rate of TPMP+ without affecting the efflux of the cation. The data are clearly inconsistent with the presence of a metabolically dependent membrane potential. Energy-dependent accumulation of TPMP+ appears to be an active process transporting lipophilic cations against their electrochemical gradient. Stationary-state distribution of TPMP+ between energized mitochondria and medium cannot be used for the membrane potential determination.