Ascorbic acid - a vitamin is observed by in vivo 13c-nmr
spectroscopy of rat liver.
K[umlaut]ustermann, Ekkehard, Joachim Seelig, and Basil
K[umlaut]unnecke.
Biocenter of the University, Klingelbergstrasse 70, CH-4056 Basel,
Switzerland . NMR Center, Massachusetts General Hospital, Building
149, 13th Street, Charlestown, MA 02129, USA
APStracts 4:0222E, 1997.
The first in vivo detection of a vitamin with nuclear magnetic
resonance (NMR) is reported for mammalian liver. Vitamin C, also
known as ascorbic acid, was monitored non-invasively in rat liver by
"whole-body" 13C-NMR spectroscopy at high field upon infusion
of [1,2-13C2] glucose into anaesthetised rats. Generally, the carbon
resonances of ascorbic acid overlap with those of other highly
abundant cellular metabolites thus precluding their observation in
situ. This problem was resolved by taking advantage of the 13C-13C
spin couplings introduced by the two covalently bound 13C nuclei in
[1,2-13C2] glucose. During glucose metabolism [5,6-13C2] ascorbic
acid was synthesised, which also exhibited characteristic 13C
homonuclear spin couplings. This feature enabled the spectral
discrimination of ascorbic acid from overlapping singlet resonances
of other metabolites. Quantitative analysis of the spin coupling
patterns provided an estimate of the turnover rate of hepatic vitamin
C in vivo (1.9+/-0.4 nmole/min/g) and a novel approach towards a
better understanding of optimum vitamin C requirements in humans. The
results obtained in vivo were confirmed with high resolution proton-
and 13C-NMR spectroscopy of liver extracts.
Received 27 May 1997; accepted in final form 1 October 1997.
APS Manuscript Number E240-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 29 October 1997