The formation of cholest-5-ene-3β,26-diol as an intermediate in the conversion of cholesterol into bile acids by liver mitochondria

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Abstract
1. When [14C]cholesterol was incubated with rat liver mitochondria, radioactive 26-hydroxycholesterol, 3β-hydroxychol-5-enoic acid and other bile acids were isolated from the incubation mixture. 2. In the absence of added 26-hydroxycholesterol, the specific radioactivity of the 26-hydroxycholesterol formed from [14C]cholesterol during the incubation was higher than that of the 3β-hydroxychol-5-enoic acid. Addition of increasing amounts of 26-hydroxycholesterol led to a progressive fall in the specific radioactivity, and to a progressive increase in the mass, of the 3β-hydroxychol-5-enoic acid recovered at the end of the incubation. 3. It is concluded that 26-hydroxycholesterol is an intermediate in the formation of 3β-hydroxychol-5-enoic acid from cholesterol. 4. Comparison of the specific radioactivity of the 26-hydroxycholesterol formed in the incubation mixture with that of the added [14C]cholesterol indicates that endogenous cholesterol in mitochondria is accessible to cholesterol 26-hydroxylase.