The uptake of choline by rat liver mitochondria.

1. Rat liver mitochondria can accumulate choline against a concentration gradient. Maximally about 30 nmol choline per mg mitochondrial protein are found in the matrix space. 2. The process of choline uptake is biphasic. After a rapid uptake of 1.5-15 nmol per mg protein, a slower uptake occurs if an energy supply is present. In the absence of energy, only the rapid uptake is found. 3. The inhibition of uncoupler-stimulated choline oxidation by cations is the result of an inhibition of choline uptake.