Formation of C21 bile acids from plant sterols in the rat
- Univ. of Oslo, Rikshospitalet (Norway)
Formation of bile acids from sitosterol in bile-fistulated female Wistar rats was studied with use of 4-14C-labeled sitosterol and sitosterol labeled with 3H in specific positions. The major part (about 75%) of the 14C radioactivity recovered as bile acids in bile after intravenous administration of (4-14C)sitosterol was found to be considerably more polar than cholic acid, and only trace amounts of radioactivity had chromatographic properties similar to those of cholic acid and chenodeoxycholic acid. It was shown that polar metabolites were formed by intermediate oxidation of the 3 beta-hydroxyl group (loss of 3H from 3 alpha-3H-labeled sitosterol) and that the most polar fraction did not contain a hydroxyl group at C7 (retention of 3H in 7 alpha,7 beta-3H2-labeled sitosterol). Furthermore, the polar metabolites had lost at least the terminal 6 or 7 carbon atoms of the side chain (loss of 3H from 22,23-3H2- and 24,28-3H2-labeled sitosterol). Experiments with 3H-labeled 7 alpha-hydroxysitosterol and 4-14C-labeled 26-hydroxysitosterol showed that none of these compounds was an efficient precursor to the polar metabolites. By analysis of purified most polar products of (4-14C) sitosterol by radio-gas chromatography and the same products of 7 alpha,7 beta-(2H2)sitosterol by combined gas chromatography-mass spectrometry, two major metabolites could be identified as C21 bile acids. One metabolite had three hydroxyl groups (3 alpha, 15, and unknown), and one had two hydroxyl groups (3 alpha, 15) and one keto group. Considerably less C21 bile acids were formed from (4-14C)sitosterol in male than in female Wistar rats. The C21 bile acids formed in male rats did not contain a 15-hydroxyl group. Conversion of a (4-14C)sitosterol into C21 bile acids did also occur in adrenalectomized and ovariectomized rats, indicating that endocrine tissues are not involved.
- OSTI ID:
- 6774742
- Journal Information:
- Journal of Biological Chemistry; (USA), Journal Name: Journal of Biological Chemistry; (USA) Vol. 265:14; ISSN JBCHA; ISSN 0021-9258
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BILE ACIDS
BIOSYNTHESIS
BODY
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
CHROMATOGRAPHY
COENZYMES
DIGESTIVE SYSTEM
GAS CHROMATOGRAPHY
GLANDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LIQUID COLUMN CHROMATOGRAPHY
LIVER
MAMMALS
MASS SPECTRA
METABOLISM
METABOLITES
NAD
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
RATS
RODENTS
SEPARATION PROCESSES
SITOSTEROL
SPECTRA
STEROIDS
STEROLS
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES