Side chain hydroxylation of cholesterol, campesterol and β-sitosterol in rat liver mitochondria

• Main Authors: L Aringer, P Eneroth, L Nordström
• Format: Article
• Language: English
• Published: Elsevier 1976-05-01
• Series: Journal of Lipid Research
• Subjects: 24-, 25-, 26-, and 29-hydroxylation; hydroxyalkylated Sephadex LH-20; Thin-layer chromatography; Gas-liquid chromatography-mass spectrometry
• Online Access: http://www.sciencedirect.com/science/article/pii/S0022227520369832

The extent of the side chain hydroxylation of cholesterol, campesterol (24 α-methylcholesterol), and β-sitosterol (24 α-ethylcholesterol) in rat liver mitochondria has been compared. Two β-sitosterol metabolites, tentatively identified by liquid chromatography, thin-layer chromatography, gas-liquid chromatography, combined with radioactivity detection, and gas-liquid chromatography-mass spectrometry as the 26- and 29-hydroxy derivatives, were formed in the proportion 1:1. The sum of 26-hydroxy- and 29-hydroxy-β-sitosterol obtained amounted only to about one-fourth of the yield of 26-hydroxycholesterol. Campersterol appeared to give rise only to 26-hydroxycampesterol (tentatively identified), which was formed in similar yields as 26-hydroxycholesterol (0.2-0.4%). The formation of 29-hydroxy-β-sitosterol but not of 28-hydroxycampesterol indicates that the omega-hydroxylation of the steroid side chain is dependent on the length of the side chain. Cholesterol gave rise to identifiable amounts of a 25-hydroxy derivative but the formation of 25-hydroxy derivatives of β-sitosterol and campesterol could not be established with certainty. 24-hydroxycholesterol was also found to be formed in the mitochondrial system. The ratio between the yields of 26- and 25-hydroxychoelsterol ranged between 2 and 3, and that between 26- and 24-hydroxycholesterol was about 10.