Measurement of rate of appearance of hepatic udp-glucose in vivo in
rats: relation to glycogen deposition and labeling patterns.
Hellerstein, Marc K., Amy Letscher, Jean-Marc Schwarz, Denise
C[acute]esar, Cedric H. L. Shackleton, Scott Turner, Richard Neese,
Ken Wu, Sandra Bock, Suzanne Kaempfer.
Department of Nutritional Sciences, 309 Morgan Hall, University of
California at Berkeley, CA 94720-3104; Division of Endocrinology and
Metabolism, Department of Medicine, University of California, San
Francisco, 1001 Potrero Avenue, San Francisco, CA 94110; Children's
Hospital of Oakland Research Institute, Oakland, CA
APStracts 3:0216E, 1996.
We previously described an isotopic method for quantifying the rate of
appearance of hepatic UDP-glucose (Ra UDP-glc) and the direct entry
of glucose into hepatic UDP-glucose (UDP-glc) in humans. Here, the
method is tested in depth in rats. The basic principles are that
dilution of labeled galactose in hepatic UDP-glc, sampled non
-invasively by the xenobiotic- glucuronate (GlcUA) method, reveals Ra
UDP-glc. First, labeling patterns in secreted acetaminophen-GlcUA
were compared to hepatic glycogen and plasma glucose, by using mass
isotopomer distribution analysis from [2-13C]-glycerol. Labeling was
consistent with common precursor pools of glucose-6-phosphate and
triose-phosphate for all end-products studied, in fasted, iv glucose-
and iv fructose-infused states. Next, [1-3H]-galactose was
administered. After a 24-h fast, Ra UDP-glc was 25.0 + 1.7 [mu]mol
/kg body wt/min and rose to 57.7 and 72.7 [mu]mol /kg/min at iv
glucose infusion rates of 111 and 167-194 [mu]mol /kg/min,
respectively. Liver glycogen deposition correlated closely with Ra
UDP-glc (R2 = 0.76) although the turnover value was roughly 50%
higher than the net deposition rate. In conclusion, the turnover of
an intrahepatic metabolite, UDP-glc, can be measured non- invasively,
and RaUDP-glc correlates with liver glycogen deposition in rats.
Received 11 March 1996; accepted in final form 20 August 1996.
APS Manuscript Number E118-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996