Limits for the use of (18O)cholesterol and (18O)sitosterol in studies of cholesterol metabolism in humans.
Biomed Environ Mass Spectrom
; 17(6): 463-70, 1988 Dec.
Article
en En
| MEDLINE
| ID: mdl-3240373
ABSTRACT
The present study was undertaken in order to determine whether 18O-labeled sterols could be used in place of 14C-sterols in clinical studies of cholesterol metabolism. (3 beta-18OH)Cholesterol and (3 beta-18OH)sitosterol were simply and inexpensively synthesized and precisely and accurately quantified by gas chromatography/mass spectrometry. 18O-Sterols added to fecal homogenate and saponified were completely recovered. However, in a series of validation studies in humans, the fecal recoveries of orally administered (18O)cholesterol and (18O)sitosterol were significantly lower than the recoveries of 14C-sterols given simultaneously. We found that the losses were largely limited to the coprostanol and ethylcoprostanol fecal metabolites. In vitro fecal incubations of 18O-sterols and unlabeled water or of unlabeled sterols with H2(18)O indicated that the losses occurred during fecal bacterial metabolism and were likely due to 3 beta-oxygen exchange with the oxygen of water, possibly via a 3-ketosteroid intermediate. These data indicate that (18O)cholesterol and (18O)sitosterol are invalid tracers for the measurement of human cholesterol metabolism by methods based on fecal sterol recovery.
Buscar en Google
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Sitoesteroles
/
Colesterol
/
Heces
Idioma:
En
Revista:
Biomed Environ Mass Spectrom
Asunto de la revista:
BIOQUIMICA
Año:
1988
Tipo del documento:
Article