Newly synthesized cholesterol in human bile and plasma:
quantitation by mass isotopomer distribution analysis.
Empen, Klaus, Kerstin Lange, Eduard F. Stange, and J[umlaut]urgen
Scheibner.
Department of Internal Medicine, Division of Gastroenterology,
Medical University of L[umlaut]ubeck, L[umlaut]ubeck, Germany
APStracts 3:0154G, 1996.
The purpose of this study was to quantitate the contribution of newly
synthesized cholesterol to bile and plasma in humans. Eight healthy
volunteers were intravenously infused with 0.125 mmol [1-13C]acetate
per kg per h for 15 h. During continuous enteral nutrition plasma
aliquots and samples of duodenal bile were collected hourly. The
trimethysilylether of unesterified cholesterol was analyzed by gas
chromatography/mass spectrometry for quantitation of the mass
fragments M+0 (m/z 368), M+1 (m/z 369), M+2 (m/z 370), M+3 (m/z 371)
and M+4 (m/z 372). The fractional syntheses of plasma and biliary
cholesterol were determined using mass isotopomer distribution
analysis (MIDA). After 6 h of infusion, the [13C]enrichment of the
acetate pool remained constant at 12 %. The fractional synthesis
increased continuously during [13C]acetate infusion and reached 4.2 %
and 5.3 % in cholesterol of plasma and bile, respectively. Both were
highly correlated but the fractional synthesis of biliary cholesterol
exceeded that of plasma (p < 0.05). It may be concluded that the
contribution of de novo cholesterol synthesis to bile exceeds that to
plasma but is minor in man.
Received 2 July 1996; accepted in final form 31 July 1996.
APS Manuscript Number G262-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996