In vivo nmr investigation of intramuscular glucose metabolism in
conscious rats.
Jucker, Beat M., Alexander J. M. Rennings, Gary W. Cline, Kitt Falk
Petersen, and Gerald I. Shulman.
Department of Internal Medicine, Yale University School of
Medicine, New Haven, CT
APStracts 4:0075E, 1997.
In vivo 13C nuclear magnetic resonance (NMR) spectroscopy was used to
quantitatively determine the rates of muscle glycolysis, glycogen
synthesis, pyruvate dehydrogenase (PDH) and pyruvate carboxylation
flux in the hindlimb of conscious rats. 13C NMR spectroscopy was used
to observe 1-13C glucose label precursor incorporation into
intramuscular 1-13C glycogen, 3-13C lactate and 3-13C alanine during
a hyperglycemic (11 mM)/hyperinsulinemic (10 mU/kg/min) clamp. The
glycogen synthesis rate was calculated to be 224+/-23 nmol/g/min. The
kinetic data obtained from the label turnover in the intramuscular C
-3 lactate and C-3 alanine metabolite pools as well as in plasma C-3
lactate and C-3 alanine was combined with a steady state rate
analysis to determine the glycolytic flux (Vgly=67.4+/-10.1
nmol/g/min). Steady state isotopomer analysis of glutamate and
pyruvate in skeletal muscle tissue extracts was used to determine the
anaplerotic contribution of substrate via pyruvate carboxylation
(Vpc). The pyruvate dehydrogenase flux (Vpdh) was calculated after a
steady state flux correction for Vpc. Calculated values of Vpc and
Vpdh were 24.8+/-4.3 and 110.0+/-18.7 nmol/g/min respectively. In
addition, 2-13C acetate was used in a separate study to determine
that pyruvate carboxylation was the major pathway for anaplerosis in
skeletal muscle under conditions of hyperglycemia/hyperinsulinemia.
Received 26 December 1996; accepted in final form 26 March 1997.
APS Manuscript Number E626-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 3 April 1997