The formation of lithocholic acid, chenodeoxycholic acid and alpha- and beta-muricholic acids from cholesterol incubated with rat-liver mitochondria.

1. When rat-liver mitochondria were incubated with [4-(14)C]cholesterol in the presence of a soluble supernatant fraction, various steroids more polar than cholesterol were formed. These included 3beta-hydroxycholest-5-en-26-oic acid, 3beta-hydroxychol-5-enoic acid, lithocholic acid, chenodeoxycholic acid and alpha- and beta-muricholic acids. 2. All the radioactive C(24) bile acids recovered were in conjugated form, probably as taurine conjugates. 3. The formation of 3beta-hydroxychol-5-enoic acid from cholesterol shows that liver mitochondria are capable of carrying out the oxidative removal of the isopropyl unit of the side chain before any modification has occurred in the ring system.